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Stark, A.E., and Banner, R. Bruce. (2013). "Biodosimetric Tools for Measuring Induced Isomeric Transition in Inverted Paired States." International Journal of Radiation Biology 89.9, 43-85.

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"Welcome to Stark Tower," Tony announces, turning so that he's framed against the tall glass doors and spreading his arms wide to encompass the whole building, repair crews and all.

"I've been, actually." Bruce sounds ironic, but he's smiling at Tony's little presentation, willing to go along with him. Tony grins in answer and slips through the doors, waving Bruce to walk towards him as he walks backwards.

"Right, right, but you haven't seen R&D yet," he says impatiently. "It doesn't count as seeing Stark Tower if you were lolling around too naked and exhausted to enjoy the fancy science toys. Hi Celia."

"Hello, Mr. Stark," Celia replies from the front desk. "Is there anything I can do for you today?"

"You can ensure that Dr Banner here is given a warm welcome and anything he needs, basically for the foreseeable future."

"Yes, sir." Celia picks up the phone.

"Uh, I don't know how long I'm going to be staying – " Bruce begins, but Tony's already walking away from that.

"This is my private elevator. I'll give you the code, though; you probably have a good reason not to get stuck in a tiny metal box with ten other people. You look fabulous in that shirt, by the way. The yellow is really fetching on you."

"It's your shirt."

"Is it?"

They ride the elevator up seventy or so floors, and when the doors open Bruce's reaction is everything Tony was hoping for. Slack jaw, wide eyes, maybe a bit of drool, the whole thing. He knew it.

"Like I said," Tony grins, nudging Bruce with his elbow. "Candyland. And this is just the first floor."

Bruce's eyes dart around, taking in the huge gleaming open space filled with every toy off the physicist's wish list, the little machine shop at the back (there are bigger shops elsewhere, but sometimes you need something right away and don't want to have to travel to get to your vacuform), the new baby particle accelerator Tony designed, the cozy little lounge area that Tony had built on each floor for naps and snacks and makeouts.

"How long did you say you wanted to stay?" Tony asks, taking off his sunglasses and folding them neatly into the breast pocket of his suit. Bruce has staggered forward two or three steps, apparently unconsciously, drawn by the incredible magnetism of nerd to science.

Slowly, he turns around to face Tony. "Below the belt, Stark," he says, but he's smiling all over his face.

"Oh please," Tony says, slinging an arm around Bruce's shoulders. The yellow really does look great on him. "Call me Tony."

-

Science and flirting aside, Tony absolutely does not intend to start having sex with Bruce. Or with the Hulk, for that matter.

It just sort of works out that way.

Really it's Bruce's fault, with his tweedy professor act and his wry self-effacing manner; Tony never could resist an introvert, and Bruce is the world's greatest introvert (except for when he's the world's greatest extrovert, of course; it's delicious). Tony doesn't know very many people who are a) superheroes, b) as smart as he is, and c) fascinating science projects in and of themselves – it's basically just Tony himself, Bruce, and Reed Richards, and Richards is a penis – so it makes sense that Tony would be interested. On top of that, Bruce turns out to be funny, interesting, and good at MarioKart (more points in his favor over Richards) so really there's nothing else for Tony to do but adopt him.

And once he's cajoled Bruce into moving into Stark Tower, Bruce is just there all the time, full of patience and good humor, ready and waiting to be cajoled into other things. Tony cajoles Bruce into hanging out with him in the labs, into helping him design new radiation shielding for the suit (since he might be called on to take it into space again), into letting Tony help him invent Asgardian energy detectors. Tony cajoles Bruce, meeting less resistance than he anticipated, into coming down to SHIELD headquarters with him for what they're optimistically calling Avengers Strategy Meetings and what are really just Clint throwing spitballs at everyone with disgusting accuracy while they all try to figure out how to work together without killing one another. He cajoles Bruce into watching Star Trek with him, and into having dinner with him every night he's not having dinner with Pepper. He even cajoles Bruce into coming out on missions with them, their team, The Avengers, more and more, solving the rash of frankly bizarre crises that now seem to face the city on a roughly weekly basis. Bruce always, always goes along with Tony's cajoling, always accepts it with enthusiasm and humor, and he doesn't seem to mind having been suddenly promoted to Tony Stark's Best Friend.

All of that goes so well, in fact, that Tony almost doesn't notice himself cajoling Bruce into making out with him, it's just such a natural extension of their established cajoler-cajolee relationship. He flirts, and Bruce flirts back, the way people do when they tell themselves they're just humoring Tony. He gets into Bruce's personal space, and Bruce doesn't back away, stays easy and calm as he talks about electrons. So it's kind of a shock after a few months of successful cajoling, when Tony backs Bruce up against a wall and kisses him, to find that Bruce isn't so easily cajoled on this particular point.

Bruce pushes Tony off him, grip tight and unhesitating on Tony's shoulders, which Tony can't help but register as promising even if Bruce is pushing in the wrong direction. Tony pulls back, letting Bruce have those six inches but not moving his arms from where he's bracing them against the wall, hemming Bruce in, holding him in place. Tony is very, very good at sussing out peoples' kinks, and he pegged Bruce as the guy who wants to be tied up from day one. The flush to Bruce's face and the way he licks his lips involuntarily tell Tony that he's probably not wrong.

"What?" Tony asks, disgruntled.

"I can't," Bruce says, in that apologetically steely tone that he gets sometimes.

Tony shuffles through potential scenarios in his mind, looking for an explanation for this behavior, trying and rejecting each one in turn – Bruce is obviously into sex, given his SHIELD file and the porn that Tony's found on his computer, and obviously into basically all types of human bodies in that delightful adorable pansexual objectivist scientist way (again, given said porn), and Bruce is of course attracted to him, Tony Stark, because come on, and –

"Is this about Pepper? Because I'm allowed to fuck other people. Or, you know, we both are, though there are a shitload of rules involved and frankly I've never had a relationship that came with a notarized contract before but actually it seems to be working? And boy could I tell you some stories about Pepper and some of her beaus, although, actually, no, I can't, that's in the contract come to think of it – "

Tony is shut up the one and only way he likes to be shut up, when Bruce closes the gap between them and kisses his mouth, soft and lush and regretful. Then he pulls back again, and pushes Tony's shoulders harder – yeah, that quiet composed strength would clearly be awesome in bed – to hold him at arm's length.

"It's not about Pepper. Though that is nice to know. And very . . . informative." Bruce makes a weird frowny face that reminds Tony of the time two weeks ago when the Hulk swallowed a bomb that they found strapped to a giant mutant HYDRA butterfly. Like he's having trouble digesting something. Tony wonders briefly if the Hulk ever shits, and if he doesn't what happened to the bomb, then mentally waves that line of thought away as probably unrelated to their present conversation.

"It's the, uh, other guy. I can't get – too excited." Bruce says gently, after a minute, when it's clear that Tony's too lost in thought to deduce the answer on his own.

Tony blinks.

"I – what, seriously?" His mouth moves for a second without any words coming out of it, which is a new experience for him. "But – I – it's nothing like the same thing! I mean, unless you like your sex with plenty of rage and pain, and I mean, I would have no objection, but surely we can find other options . . . " he trails off, taking in Bruce's amused/sad expression. It's kind of awful that he's come to know it as Bruce's default expression. "Have you tried it? Did you try it with someone, and you hulked out?"

Tony's seen the Hulk's cock. Tony would happily admit to having had one or two stray fantasies about the Hulk's cock, but mostly just in that vague way that he has sexual fantasies about all the hot buff deadly superheroes he hangs out with. He can only imagine what it would feel like to have that thing inside you, but then, his imagination is extremely vivid and detailled. Having the Hulk's cock inside you unexpectedly, though, would be . . . bad.

Bruce's lips press together. "No, but – one time, with my old girlfriend, I could feel it about to happen. I know what it feels like when it's coming on, Tony, it's unmistakable. And she wasn't – there wasn't any pain or discomfort, I was just. Excited." He cracks a self-deprecating smile. "So, I can't."

Tony takes a step back, puts a hand over his mouth, starts to pace in short quick three-step circuits. "So all that porn on your computer, that's just, what? For intellectual purposes?"

"I love your dedication to personal privacy."

"Oh please, it's not like I opened any of the files. Or, well. Not many of them, anyway." He gets distracted for a second thinking about how resourceful Bruce had been at hiding the porn on his computer, and how nerdy his folder names had been – god Tony wants to sex his brain so hard – then breaks himself out of it and points an accusing finger at Bruce. "Anyway, don't change the subject. You can totally come without hulking."

"Sometimes," Bruce shrugs. "If I do a set of breathing exercises first, put myself into a relaxed state, take an ambien or two, focus exclusively on the actors instead of on my own body . . . "

So that's what the porn is for. Tony snaps his fingers. "All right, there you go, we've got some data. I can work with that. Seriously, Bruce, I do not mind working around your little . . . problem."

Bruce hesitates. Tony bets that there aren't a lot of people who've pursued Bruce as a sexual partner after the conversation about how sex turns him into a giant green smashing machine, which means he's probably got fewer ingrained lines of defense from here on out. Excellent.

"Tony, the Hulk isn't erectile dysfunction, I don't – "

Tony moves forward to put himself where he was before, backing Bruce up to the wall, arms braced on either side to keep him from escaping. He presses a knee between Bruce's legs and Bruce shifts slightly to arch against him, just a little, like his body is seeking out contact he knows he shouldn't let himself have.

"I trust you," Tony breathes, kissing him once, as chastely and gently as he can. "It'll be fine. I trust you. C'mon."

"You could – surely you could find someone to sleep with who doesn't present this problem. Like, anyone else in the world, maybe."

"Mmmm, yeah, I could, but I want you," Tony says easily, biting at Bruce's jaw. Bruce doesn't seem to have anything to say to that, so Tony wraps his arms around Bruce's shoulders and kisses him again, deeper this time, but still slow, easy.

"You're really used to getting what you want," Bruce murmurs against Tony's mouth, chuckling, and when Tony kisses him next it's with his standard-issue cocky grin.

"Always."

Bruce keeps making disapproving noises while he kisses Tony back, and closes his eyes tightly and breathes shakily when he puts his hands on Tony's body. His fingers dig into Tony's shoulders and pull him in, pull him in the right direction this time, making him fall in towards Bruce and lose himself in hot, biting, restrained kisses.

-

So, but, it turns out that Bruce was right, Tony was wrong, and Tony's a big enough amazing enough genius to admit that sometimes he's wrong, which he will totally do the moment that Bruce comes back to hear it.

They did go slow, is the thing; Tony didn't try to push, didn't try to rush. It took days of just making out before Bruce would even step foot in a bedroom, where he'd promptly folded himself up on the floor and told Tony not to bother him for a while. And Tony had done it, just let Bruce take a pill and do some yoga breathing stuff and get ready and the whole time he was a good boy and just watched from the other side of the room, twitchy and anxious and slipping a hand down into his pants every now and then to relieve the ache a little. And when they finally got to it, the sex part was slow: slow kisses, slow touches, with Tony narrating every step to avoid surprises and Bruce nodding up at him dark-eyed and it was a handjob, for Christ's sake, who turns into a rage monster when receiving a handjob?

Apparently, Bruce Banner does.

Which is how Tony finds himself straddling the hips of a man turning rapidly green, writhing naked and sweaty against the sheets as he resists the change, his cock hard and leaking in Tony's hand. Bruce gasps for breath and looks up at Tony desperately, like he knows he can't keep it at bay and is begging Tony to get out, run, go get the suit or something –

Bruce's body expands beneath him, his thighs thickening with green cords of muscle and lifting Tony up so that his knees aren't even touching the bed anymore. The change is even more dramatic in the torso, in the neck, in Bruce's face, which broadens and flattens out until it looks like Bruce but also looks like someone entirely different. The Hulk even has different hair, Tony thinks calmly, as he holds on desperately to the body beneath him to avoid getting bucked off. On top of the Hulk seems like the safest place to be at the moment, and it has the additional benefit of also being the most interesting.

His brain runs through all the calculations. How quickly he could get out of this room, how quickly he could get to the nearest suit. How fast the Hulk is, how strong (Tony's done the math). How fast and strong the Iron Man suit is in comparison. How much damage the Hulk could do before someone was able to subdue him, which by the way no one on the planet has ever actually been capable of doing before, including the visiting Norse god of thunder with his special magic hammer.

And the interesting thing – the really interesting thing, Tony thinks, all this flashing through his mind in the split second between Bruce and Hulk – is that he's still got Bruce's cock in his hand, and it doesn't seem to be getting any less hard as Bruce screams and twists into a new shape.

Tony doesn't really want to see what kind of damage the Hulk might do when he's blueballed and cockblocked.

"Shhhhhhh," he says, almost involuntarily, like the monster below him is a child having a tantrum. Bruce is gone now, and it's all Hulk, strange violent eyes looking up at him, giant green hands fisting against the sheets, digging into the mattress like it's butter. Tony strokes a cautious palm down the Hulk's chest – and he's hot, so much hotter than Bruce, like he's burning up inside with all that power and anger.

"It's okay," Tony says, throat dry. He gets both his hands on the Hulk's cock, because the thing is way too big around for Tony to be able to hold it in one fist, and starts working him, slowly, just the way he and Bruce had talked about, jacking him in a gentle rhythm with tight steady pressure. "It's okay, big guy, c'mon, c'mon – "

The Hulk throws back his head and honest-to-god groans, and the sound of his voice rumbles up through Tony's body like the shockwave after an explosion, vibrating his arc reactor in its socket. He speeds up his hands, squeezing hard, cupping one palm over the head, trying to work the whole thing at once but it's like giving a handjob to a young sapling, seriously, and Tony doesn't think he's ever been more turned on in his entire life. The Hulk is writhing and tearing the shit out of the sheets, the mattress, the bedframe, and Tony pulls and squeezes and makes him writhe, gives him what he needs. The sheer power in the thighs beneath him, in the body Tony's currently spread out on top of – it's a rush, like all the best moments of Tony's life, like his first flight in the Iron Man suit, like discovering vibranium, like he's riding the proverbial fucking tiger

The Hulk's eyes snap open and his gaze locks with Tony's. The feeling that shudders through him then isn't fear and it isn't lust but it's bound up tightly with both of them, like a spiralling double helix of intense overwhelming sensation that goes straight to Tony's dick. Tony redoubles his efforts, trying to maintain his grip. Every time the Hulk shifts or thrusts beneath him it almost bucks him off, so the effect is not unlike trying to jerk off a mechanical bull, except way hotter and more dangerous.

Large green hands, easily capable of snapping a mid-sized luxury automobile clean in half (Tony's seen it, saw it last week in fact), come up to wrap around Tony's sides. His hands are huge, seriously giant. How did Tony never realize this before? The fingers span from Tony's armpits down to his waist and when he takes a deep shuddering breath he can feel them against his body, not exerting pressure but restricting the expansion of his lungs just by the weight of them, just by resting harmlessly against his skin. Tony feels dizzy with it, overwhelmed as the Hulk presses him between his two hands and just – holds him there, holds him steady.

"Yes," the Hulk growls, and oh shit Tony needs to come, needs to get some fucking friction, so he slides to the side, straddles one massive thigh, and rubs against it, keeping up his double-fisting action on the Hulk's cock as he does, and it's not enough not enough but then the Hulk's hands shift on his body and he starts to squeeze just a little and Tony gasps for breath oh jesus

"Yes," Hulk says again, through gritted teeth this time, and then starts coming all over Tony's hands and arms. Tony ducks back instinctively, because he was traumatized as a kid by that fucked up Larry Niven article about Superman's potentially deadly comeshots, but while it's copious, it's not particularly forceful, which is something of a relief.

Then he's letting go of the Hulk's giant green dick and falling forward, and now he feels the ache in his arms and wrists but he doesn't even care, just braces himself on the convenient planes of the Hulk's body and ruts against his thigh, presses his forehead to the Hulk's hot hard belly and closes his eyes and groans as he starts to come.

The Hulk starts chuckling while Tony is still panting wetly against his skin and trying to remember his own name. One of those huge hands comes up – slowly – to cradle his head, which, ow, but it's probably meant to be gentle, Tony should probably take this as a sweet post-coital snuggling thing and not as a threat to pop his skull like a grape –

The Hulk's hand drops back down to the mattress with a dull crash. "Hulk sleep now," the Hulk informs him, and just like that he's out, head falling to the side and off the hopelessly inadequate and by now rather abused pillow, mouth open and . . . and snoring. It's weirdly adorable. Though, also, super-loud.

"Well," Tony says to himself, glancing at the slightly green-tinged semen that's all over his arms, his torso, the Hulk, the bed, and – yup, the floor, too. "I guess I'll just go take a shower."

He tries not to drip too much on the way to the bathroom, where he discovers some pretty gorgeous bruises already blooming to the surface, but no real damage. Score one for distracting the Hulk with sex; the military should've tried this tactic years ago. Tony imagines the squad of Marines tasked with sexing-the-Hulk duty, and the probable safety equipment, and the procedural manual, and laughs into the hot spray of water against his face.

When he comes out of the bathroom he's whistling a merry tune and not at all surprised to see Bruce, pink and comparatively tiny, lying in the little bed-crater left by the Hulk. Tony's going to have to find a sturdier bed, or maybe build one. He takes a second to text Pepper and let her know he fucked someone – someones? does Bruce count as two people? Is he an automatic threesome? Tony includes these questions in his series of texts, which he follows with a quick self-portrait of himself making a holy-shit-I-fucked-the-Hulk face, and then tosses his phone onto a chair and moves to stand beside the bed. Bruce even looks worried in his post-hulkgasmic sleep, jesus.

He pokes Bruce repeatedly in the shoulder and then in the face until he frowns, bats at Tony's hands, and wakes up.

"Good morning, sleepyhead," Tony grins. "Do you have any idea how much semen the other guy produces when he comes? It is truly astonishing. And it's not even like I'm going to be able to find a condom that won't break." He frowns, wondering what the coefficient of friction of Hulk's superskin against latex would be. "I guess I could make some."

Bruce blinks up at him, clearly not understanding; then he twitches and visibly comes back to himself, eyes focusing on Tony. "Oh jesus," he mutters, looking around him, at the sticky handfuls of mattress ticking and the shreds of sheets and the now extremely disgusting pool of cold semen on his belly. "What – are you okay?" Sitting up, he grabs his glasses from the bedside table, and, putting them on, turns to peer at Tony's body with the intense disinterested worry of a medical doctor.

Tony sighs, drops his towel to the floor – an act which in a just universe would inspire a better, sexier reaction than Bruce's deepening frown – and spreads out his arms. "I'm fine."

"You're covered in bruises."

"Not the first time," Tony grins. Bruce raises an eyebrow at him. "Seriously, it's okay. I'll need a new mattress and possibly a new bed, but otherwise there's no harm."

Bruce, unconvinced, keeps running his hands along Tony's ribs, then along the bones of his arms, prodding gently around the edges of the worst of the bruising. Which, after a minute or two, starts to kind of give Tony a semi. It's not his fault he had a very kind and handsome pediatrician when he was a kid and developed a sort of thing for medical exams. It should be plenty obvious to Bruce, since Tony's naked and Bruce is examining his body, but apparently Bruce is more focused on making sure that Tony's not lying about having horrible internal injuries or something. After another minute or two Tony steps forward, shooing Bruce's doctor-hands away, and kneels on the bed, straddling Bruce's waist the way he had been doing half an hour ago when things started to get weird. Bruce is gross and sticky, but hell, Tony can always take another shower. Maybe Bruce will let him wash his back.

"How did you convince him to – " Bruce pauses, blinks, and then apparently the memories start to come back to him, or else he finally notices that he's sitting in a giant wet spot of light green jizz. "Tony," he says, and his voice is tight, like maybe his throat is closing up. "Did you have sex with the – the other guy? Because I seem to remember – "

"It was awesome," Tony grins. "I was a little worried at the beginning, I admit, uncharted waters and so forth, but once we both got into it I have to say it was pretty great. Sorry you couldn't be there, though." To make up for it, he leans in to kiss Bruce's mouth, but Bruce pushes him away, hard enough that Tony has to scramble off his lap and back up to his feet. Tony sighs. They're back to this. Great.

Bruce looks like he wants to yell at him, but isn't quite sure where to begin, or even what he's most mad about at the moment. Tony is extremely familiar with this look, since he receives it from Pepper, Fury, Steve, Natasha, or Hill on a pretty much daily basis, so he adopts his time-tested steamrolling defense strategy and rushes right in to cut him off.

"Oh, so what, now you're going to get all closed-off and distant and tell me we can never do that again? Seriously? Because of a couple of bruises and a slightly worse for wear mattress? Please, you don't even –"

Bruce cuts him off, speaking loud enough to drown him out. "Tony, you don't know what you're playing with. You don't know what he can do."

Tony raises an eyebrow. "I think I do, actually." He mimes his double-fisting action from earlier. "Great cardio, though I think I'm going to have to do more work on my flexors and biceps if we really want to make this a regular thing – "

"This is not going to be a regular thing!" Bruce yells, and Tony winces. It's true that sometimes this strategy only makes Pepper, Fury, Steve, Natasha, and Hill angrier, now that he thinks about it.

"I – "

"No! Tony, it's not safe, it's not – " he takes a deep breath, then pinches the bridge of his nose. "I could've killed you," he finishes, almost uninflected, a bald statement of a fact he's learned to live with, that he could be about to kill people all the time.

Tony needs a new tactic, something to bypass Bruce's usual guilt-channels. This time he doesn't touch Bruce, just goes to sit next to him on the edge of the bed, leaving a couple of inches between them. He wonders if this is the weirdest naked conversation he's ever had, and makes a note to consult JARVIS later for his list.

"What triggers the Hulk?" he asks. Bruce looks up quickly at his tone, which is the challenging, argumentative one he uses in the lab when they're working out some problem together. Whether Bruce realizes it or not, the muscles in his neck and shoulders relax slightly at the familiar context. Tony congratulates himself on achievement one unlocked.

"Pain," he responds, immediately. "Fear. Being backed into a corner and threatened. Any sudden overwhelming emotion. Any heightened physical state." He quirks his mouth, not quite a smile. "Adrenaline is indicated, but it's not the only factor by far."

"You forgot one."

Bruce, who is just as much of a genius as Tony is, which is half the reason Tony wants to bang him so much in the first place, gets it immediately, and smiles at him sidelong, that sad amused smile again. "And my conscious decision to let him take over."

He's been doing that more and more, over the past few months, letting the Hulk out to play when there are Doombots or HYDRA mutants or AIM weapons of mass destruction flying around the city. The Hulk has been pretty consistent about sticking to only smashing the bad guys when he does. There's even an adorable Youtube video of the Hulk carefully handing a rag doll back to the rescued little kid it belonged to. When Pepper saw it she'd asked Tony, only sort of as a joke, if having a transitional object of his own would help change the Hulk back into Bruce. Tony also has a theory about voluntary versus involuntary transformation, but it's not quite ready to run by Bruce yet. Maybe he'll ask Pepper about it.

"Right, better. And what triggers Bruce Banner?"

Bruce's eyebrows shoot up, but Tony can see that his brain is already working. "I've had less opportunity to study that," he says, then bites his lip and continues. "Usually I just wake up in the woods somewhere. And when I fell from the Helicarrier I think that knocked him unconscious, that was a first. Lately it's always been, you know, after big battles and such."

"So, it's normally just that the other guy gets all tuckered out and needs a nap."

"Something like that." Still smiling; good.

"Well, here's another data point for you: nothing tuckers him out like a good orgasm."

Bruce's lips twitch. "It's too bad the military didn't think of that years ago," he says, and Tony wants to dance in place. "There could be a dedicated squadron of Marines who could just follow me around, and their equipment – "

"The safety equipment alone, I know!" Tony agrees. "I would pay good money, quite a lot of good money in point of fact, to be the guy who writes that procedural manual."

Now Bruce laughs, a rich rumbling sound that reminds Tony of the Hulk.

Tony cups a hand over Bruce's naked hairy knee, pressing his advantage. "What I'm saying is, there are few things more important for you than learning ways to turn from the other guy back into yourself. And sex actually seems to be one of the safest methods we can use to poke at the border between the two of you and figure that out. And so," he concludes triumphantly, "you owe it to science, to yourself, and to the people of New York City to have tons of hot awesome monster sex with me."

"I'll think about it," Bruce says, which Tony is going to take as a win. "I've never been in quite this situation before, with the opportunity to do tests."

A thought occurs to Tony. "You've never actually hulked out during sex with anyone before today," he says slowly. Bruce gives him a puzzled look and nods.

"Yes? That's what I said before we started this."

"So, what you're telling me is, I just punched the Hulk's V-card." The enormity of the awesomeness of that is almost too much to contemplate. Tony should get some kind of award or something. A sex award. Most Daring Deflowering.

Bruce blinks, startled, then his face breaks into a wide grin. "Just be careful, Tony, I bet he'll get real cranky if you don't call him tomorrow. And maybe you should send him flowers."

Tony leans over and plants a smacking kiss on Bruce's cheek. "Nah, he already gets the handjobs. I'll get you the flowers."

-

Bruce strolls into Tony's workshop the next day with an unobtrusive little purple carnation in the buttonhole of his tweed suit jacket, which makes Tony grin to himself. He reaches out an arm as Bruce starts to walk by him and grabs a handful of Bruce's shirt – and by the sound Bruce makes, possibly a handful of Bruce's chest hair as well, whoops – and hauls him in for a kiss.

A while later, he says, "Good morning."

Bruce looks glazed, but replies calmly: "It's three in the afternoon."

"Is it? Shit, I think I was supposed to pick up Pepper at the airport."

"Of course you weren't," Pepper says, coming in the door. Knowing her, she had probably been waiting outside patiently for them to finish kissing. "I would never ask you to pick me up at the airport. What I told you was: expect Happy to be gone this afternoon, because he will be picking me up at the airport."

Tony gives her his best dazzling smile, though he can't help but notice how Bruce takes a nervous step or two back, trying to make it a little less obvious that they were just making out. They'll have to fix that.

"See, that's why I love you," he says. "You really get me."

Pepper walks up and kisses him, brief and soft, just to say hello. "I get that you're a self-obsessed absent-minded atemporal narcissist vampire, yes," she replies primly, before turning to smile at Bruce.

"Really, self-obsessed and a narcissist. Both of those."

"Yes. Hello, Dr Banner."

"Bruce, please," he stutters, taking an additional step backwards and almost tripping over a bench.

"Bruce," Pepper nods. "Bruce, it's absolutely fine that you're having sex with my boyfriend, so please stop skittering around like that. I'm not going to bite."

Tony pouts at her, and she smacks him.

"Uh, thanks," Bruce says, and tries half a smile.

Tony grins. "Let's all get dinner!"

"It's still three in the afternoon," Bruce says, but now it's a whole smile.

"I missed lunch, actually," Pepper says, "I could eat." She breaks away from Tony and falls in next to Bruce, taking his elbow as they head for the elevator. "So I hear you're taking over the radiation labs," she says, leaning in to him. "I can't tell you how glad I am to have someone in there who knows what he's doing."

"Hey," Tony says, reflexively.

"Well, I don't know if someone who blew up a radiation bomb and turned himself into a monster is necessarily the definition of 'someone who knows what he's doing,' but I do love the lab."

"Trust me, in comparison to Tony, you're doing just fine. At least you haven't given yourself cancer."

"It was one tiny melanoma, and it was benign!" Tony interrupts, nettled. It probably wasn't even because of the radiation. Probably. He pushes the elevator button with more force than is strictly necessary.

"Well, perhaps with Dr Banner around you could consider giving yourself zero melanomas instead," Pepper replies, quirking a grin. "Help me here, Bruce."

"I'll do my best," Bruce offers, as they emerge from the elevator. The two of them remain arm-in-arm as they walk out the front door of the tower and into the sunshine, where Happy is waiting next to the limo.

"It'll be nice to have a stabilizing influence around," Pepper says, letting go of Bruce's arm and giving it a little pat. "I trust you to make sure he doesn't do anything ridiculous to himself."

Tony can't help but grin at the expression on Bruce's face at that, like he's both bemused and touched to be thought of as a stabilizing influence. Tony loves Pepper a lot, so he reels her in for a big wet kiss right there on the sidewalk, not caring about the paparazzi who usually station themselves in the vicinity.

"I'm sure glad you approve of my new sex friend, Mom," he murmurs against her mouth.

"Oh God, please get in the car," Happy groans. Tony shoots a wink at him and hops in obediently.

-

"Are you serious about him?" Pepper asks, later, when Bruce has made some excuse to leave them alone.

"We've had sex once. And he had to be cheered up afterwards with science talk. And yes, of course I'm serious, you don't just have sex with gamma monsters without being at least a little bit serious about it, do you know how much work it is to jerk that guy off?"

"I can imagine," Pepper laughs. She's barefoot, pressed against him on the couch, her toes slipping up into the legs of his pants, pressing against his bare calves. "Well, have sex with him a few more times. See how it goes. Maybe I'll go to Brazil a day early, give you two some space."

"I feel compelled to point out at this juncture that Bruce is currently giving us some space." Tony says, shivering as Pepper pushes her big toe against his achilles tendon.

"So he is," Pepper agrees. "How about that."

-

"Are you close?" Tony pants, and Bruce laughs, groans, pushes forward into the circle of Tony's fist.

"Yes on both counts," he puffs. He's naked except for his socks and his glasses, body pressed full-length against Tony's, his ass grinding back against Tony's dick. Tony's braced against the wall with his pants still sort of bunched around his knees, but he's beyond caring much about that.

"So I should get off now, huh? The Hulk hasn't been so big on reciprocity the last few times."

Bruce's head falls back onto Tony's shoulder; Tony, helpless, works his teeth against the lobe of his ear.

"Or else you just don't want to get a handjob from a, a guy who can snap you like a twig."

"There's that," Tony allows. He speeds up his hand and maybe it's his imagination but it looks like Bruce starts to go a little green around the edges. "Yeah," Tony breathes. "Yeah, c'mon, turn around, get on your back – " Bruce does, breaking away with a groan and falling back onto the bed. Tony takes the opportunity to wiggle out of his pants, and Bruce takes the opportunity to put his glasses carefully out of his own reach and pull off his socks.

"What?" Bruce says, when he sees that Tony is giving him a look. "I like these socks."

"You are absolutely the cutest rage monster I know." Tony grins, slipping his tank top over his head, and lets Bruce ball the socks up and toss them into a corner before crawling on top of him and pinning his wrists. Bruce squirms and bucks against him, and when he opens his eyes Tony can see that they're starting to shade between brown and green.

"You like this," Tony says, looking down at him. "You like being restrained. And the other guy likes breaking out of restraints."

"I used to do this before," Bruce says, almost too quiet to hear, as Tony shimmies down his body. "I – oh fuck," he stops talking while Tony starts sucking, which is quite polite and gratifying and all, but Tony wants to hear the end of that sentence. He pulls off.

"Pardon? What was that?" Then he goes back down, taking Bruce deep, getting him wet.

"Getting, getting tied up," Bruce says, his hand coming down to ruffle through Tony's hair, gentle, but still somehow reminding Tony of that first time, of the Hulk's giant hand cradling his skull. "Before the experiment, I liked that." He says it really matter-of-fact, like it's no big deal, but Tony guesses that once you've been an inarticulate naked monster rampaging through New York you lose some of your hangups about shame.

Tony really wants to pursue this line of questioning further, but he's got dick in his mouth and Bruce's skin is getting hot, the muscles beginning to ripple and stretch, just slightly, beneath the skin. He makes a note to ask Bruce about it later, though, because there are definitely bondage possibilities in their future.

"Oh, oh, jesus, Tony." Bruce is twisting beneath him. Where Tony's hands wrap around his hips the skin is getting harder, rougher, greener. "Get off, get off, I'm going to – "

Tony pulls off in a hurry, because when Bruce Banner warns you that he's getting close you don't just wink and swallow insouciantly. He stays nearby, though, stays on top, because he loves the feeling of Bruce's body expanding under him, getting bigger, going out of control.

"Do it," Tony says, riding him, getting a hand on his own dick. "Do it, let go, c'mon, do it on purpose, Bruce, just let it happen – "

Bruce falls back against the pillows, eyes shining emerald, takes a slow, even breath, shoves his cock up against Tony's ass, and changes, smooth and easy like he does in the field, like it's allowed, like it's what he wants.

Tony jerks himself a couple more times and it's over, he's coming all over what is now the Hulk's stomach, almost losing his balance as he shakes through it, falling eventually and smacking his palms against the Hulk's chest to brace himself. Distantly, he feels the Hulk wrapping arms around him, holding him steady, fucking up between Tony's thighs in obscenely powerful thrusts. Tony blinks and realizes that the Hulk is looking him in the eye, and the moment he looks back the Hulk grunts and grits his teeth in what might be a smile.

"Mouth," he growls, and Tony blinks again.

"I can't do it for you like I do it for Bruce, buddy – " but he shuffles back down anyway, because he's not going to say no, and because his thighs already feel chafed. He does give it the old Stark try, but he can't quite get his mouth around the head, so he settles for two hands and a lot of licking and lipping. Tony suppresses a shudder as he thinks about what it would have been like to have it in his mouth while it changed, have Bruce's cock expanding to fill the space inside of him.

It doesn't take long – it never does, with the Hulk, who isn't really into delayed gratification – and soon there's a thousand pounds of green rage monster twisting and bucking beneath him, roaring, coming all over everything. Tony really has to invent those condoms, seriously, but it's one of those things where he only ever thinks about it when the Hulk is coming all over one of the bedrooms, never when he's down in the polymer lab.

When Tony looks up a second later, the Hulk is actually panting for breath, which Tony hasn't ever seen before outside of battle, and grinning his weird blunt-toothed grin.

"Bruce now?" the Hulk offers, and Tony manages an enthusiastic nod, once he's picked his jaw up from the floor.

"Thanks, big guy," he stammers, a second later, as the giant green body begins to shrink down again. In seconds, Bruce is blinking up at him, and Tony scrambles belatedly to get his knee out of Bruce's groin and his elbow out of his solar plexus. It's weird how delicate Bruce always seems, after, even though he's broad-chested and strong enough by human standards. Tony collapses beside him, trying to avoid the wet spot, which is futile since the entire bed is a wet spot. And torn to shreds again. He's basically keeping an entire mattress store in business these days.

"This is going to sound gross," Bruce drawls, as Tony snuggles in against his shoulder, "but I notice that the pools of greenish semen are still remarkably warm. I didn't sleep?"

"The other guy offered to switch back to you," Tony murmurs, like it's no big deal, just a cooperative considerate green rage monster as per usual. "Neither of you was unconscious."

"Huh. There's a data point." Bruce uses a sheet to clean himself off as best he can, then tosses it to the floor.

"I told you this would be scientific." Tony presses two fingers against Bruce's jaw, uses them to turn his head towards him. He smiles, then kisses him slowly.

"I have a request," Bruce says, a minute or two later, and immediately stops making eye contact. Tony's interest is piqued.

"Of course," he says, magnanimously.

Bruce hesitates for a few seconds, then swallows and says, "Could you fuck me?" At Tony's raised eyebrows, he hastens to explain. "Like this, I mean, like now. When I'm, when he's done. I don't think I could get it up again, he'd probably stay dormant, and it would feel – I'd like to know how it feels."

Tony considers this for roughly 0.68 seconds, then springs up off the bed and stalks towards the dresser. "I've got some Viagra around here somewhere, hang on."

Bruce laughs and stretches, lacing his fingers behind his head. "Remind me to make you something better tomorrow. That stuff is amateur-level."

Tony gazes at him adoringly while he pops the pill in his mouth. "Now, see, I knew there was a reason to keep you around."

The fucking feels amazing, is how it ends up feeling, at least to Tony; Bruce is pliant and relaxed and soft beneath him, so soft and squishy and real, his voice breaking with quiet breathy moans that hit Tony just as hard in the arc reactor as the Hulk's much higher-decibel sex noises. Tony fucks him, and fucks him, until they get into a rhythm, until they get into a place where it feels like it's never going to end and doesn't need to. Bruce's hands fist what's left of the sheets as he shoves back against Tony's easy rolling thrusts, and he makes noises like he's coming apart, like Tony's breaking him into pieces. Tony fucks him as gently as he can, slow, almost agonizingly slow, and it feels like hours before he comes in Bruce's ass, shuddering and spilling into Bruce's body, trying hard not to leave any finger-shaped bruises on his hips.

After, Bruce rolls back over and gives him a lazy, satisfied grin. "Thank you," he says. His cock is half-hard and his skin is a little green here and there, but both effects are fading fast now Tony's stopped fucking him.

"Anytime," Tony replies faintly.

-

"I'm worried that you aren't actually capable of consent," Bruce says, a couple days later.

"Hey!" Tony's too exhausted to actually listen to words, but that sounded like an insult. His outrage is muffled by Bruce's naked shoulder, against which Tony is currently pressing his whole entire face. He's got a leg slung over Bruce's thigh and an arm over Bruce's waist and he's pretty sure if Bruce were to stand up he could just cling on like a toddler.

"With the H – with him, I mean. The other guy. You can't say no, can you? In the middle of it."

Tony trails his fingers over Bruce's belly, lightly, playfully. For once, he doesn't say the first thing that comes to his mind, which is "feature, not a bug." He figures it's too early in their relationship for that confession. Hell, it might always be too early in their relationship for it.

"I don't mind?" he tries, but doesn't sound convincing even to himself.

"It's just – it's another way in which this whole thing is incredibly dangerous. What if he hurts you? How can you make him stop?"

"Can we teach the Hulk about safewords, do you think?"

Bruce snorts in derision, but that's because he has a much lower opinion of the Hulk than Tony does. Tony bets he could teach the Hulk about safewords.

They lie there in silence for a little while. Tony keeps tracing his fingers over Bruce's skin; he's so soft and cool like this, so yielding. Sometimes Tony imagines that Bruce-as-Bruce is spongy, porous; that Tony could push his fingers right through him if he wanted to, and that it wouldn't hurt either of them a bit.

Bruce sighs. "I wake up every morning and tell myself I'm not going to do this anymore. That it's – it's crazy, pretending that this isn't going to end in disaster, that I'm not going to kill you, that I'm not just kidding myself and that I – he – can be, be domesticated – "

"Hey, hey, hey," Tony interrupts, desperately, a thread of panic tugging inside him. He doesn't know if he can deal with Bruce freaking out over this.

"I tell myself I'm going to stop, and then I don't, and then you're just, you act like he's not even scary, like it's no big deal. What the hell is that, Tony? How can you do that?"

"Well, for one thing, I've heard him snore." The line works like it's supposed to, cutting into Bruce's – whatever – emotions – and making him laugh a little, despite himself.

"Yeah, it's weird how you two are so much closer than he and I are," Bruce sighs, rubbing a hand over his face.

"Ah, see, you're just jealous of our intimate relationship," Tony points out. He nudges his head at Bruce's upper arm until Bruce gets the hint, moves up the bed enough to wrap his arm around Tony's shoulders, slip Tony's head against his chest. "Classic sibling rivalry. Don't worry, there's enough of me to go around."

Bruce lifts his other arm, trails a finger over a yellowing bruise on Tony's torso. It's one of many. "You sure about that?"

"Yes – oh! yes, okay, definitely," Tony replies, as Bruce's finger presses down painfully into the bruise. "Wow, and here I thought you were the type who liked it on the bottom."

"I liked getting tied up," Bruce corrects absently. "Doesn't mean I'm not a . . . " he trails off, realizing what he was about to reveal.

Tony supplies the word for him. "A sadist?"

"Anyway," Bruce coughs. "I don't do that anymore."

"Hmmm."

-

Pepper is finally back in town that weekend, so Tony meets her for lunch as a civilized preamble to getting her back home so they can rip each others' clothes off. He stands and kisses her mouth when she comes in to the restaurant, restrained and polite per the terms of their contract, though Tony does push it a little by slipping her some tongue. Of course when he pulls away Pepper's eyes immediately flick down to his collar, to the fresh bruise that isn't quite hidden by his shirt.

"I see you and Bruce are making it work," she comments as she sits and opens her menu.

"Baby, you ain't seen nothing yet," Tony grins. "How was Brazil?"

"Gorgeous. Hot. Sweaty." She peeks at him over the top of her menu, smiling sweetly, perfectly aware that she's setting him up with that line. The great thing about Pepper is that she knows how desperately Tony needs a straight man, and knows quite well that the straight man is the true genius of any comedy duo. Tony is so very glad she's back.

"Yes! Indeed. I saw the photo you texted me. What was his name, Diego? Flavio? Fabio?"

"Thiago," Pepper sighs. "Though unfortunately I can't show you any battle wounds; the little dear wanted all the bruises for himself."

"I keep telling you, you visit Catholic countries, you're going to find men who want to be crucified, it's not complicated – "

"Oh, yes, so different from being here with you, you'd never get yourself up on a cross – "

" – really have to try something new, Pep, all these gorgeous men with martyr complexes, I don't know what you see in them – "

" – and anyway who says I don't like a little Pontius Pilate roleplay now and then?" Pepper grins at him; he lifts her hand to his mouth and kisses it.

"I'm sure you'd be stunning in a toga and a fat suit," he says earnestly. "Maybe a greasy wig."

"Of course," Pepper agrees airily.

-

Later, when they've had a proper and more extensive hello, Pepper trails her hands over the map of bruises that dot Tony's body. For a moment Tony tenses up, positive that she'll say something – are you sure it's safe, Tony, are you sure you should be doing this, are you sure that's what you want, isn't this unhealthy – but she doesn't, she doesn't, and he breathes and reminds himself that there's a reason he's with Pepper, and it's because she knows him better than anyone in the world. It's because she knows when he's being self-destructive in a bad way and she knows when he's not, and Tony doesn't even know how she knows that because half the time he doesn't know himself, but somehow it works.

"What's it like?" is what Pepper ends up saying instead. Tony kisses her.

"It's – amazing. Terrifying. Incredibly, deeply sexy, Pep, you should see him – "

"I doubt very much that Dr Banner would let me."

Tony blinks. "You don't – no?"

Pepper shoves at his side until he rolls over on his back, then climbs on top of him. "I think it's a miracle that he lets you, honestly. You should be honored. But what I meant was," her knee between his legs, her fingers sliding behind his balls, "what's it like when he fucks you."

"I – he doesn't," Tony says, so surprised that he can't even come up with a snappy reply, a way to cover up the truth. Pepper slips her index finger inside of him, slow, easy. Probably something like one-seventy-fifth the circumference of the Hulk's dick, Tony can't help thinking. "He hasn't."

"Really?" Pepper's finger stops moving. "It's been weeks."

"Well, forgive me for taking it slow and working my way up to putting monster cock inside my ass!" Tony gesticulates at the ceiling. Pepper rolls her eyes and shoves her finger deeper. "Do you know what kind of force the Hulk exerts? Even when he's not – oh, jesus Pep, yes – not trying?"

"I do," Pepper says evenly, stroking in and out of him with two fingers now. "Frankly, that's why I thought it'd be the first thing you'd do."

-

Around that time construction finishes on the new Avengers levels and the rest of the team starts moving in; first Steve, who's glad to be out of SHIELD housing, then Natasha and Clint, and finally Thor, who had been off in New Mexico for a few weeks visiting his lady friend, who turns out to be Jane fucking Foster of all people. Tony and Bruce geek out over that for a few days when they find out, Bruce going especially dreamy-eyed since she actually works in his field and has been publishing a lot of cool shit on gamma lately. Tony wonders if Thor could be persuaded to persuade her to move to New York; he's been trying to hire her for years.

The others settle in and it's kind of nice, having the occasional party and shared hangout spaces, spending time with his team when they're not fighting shoulder to shoulder against giant floating eyeball monsters. He and Bruce and Pepper usually sit together on the couch for movie night, and if any of the others notice that he's isn't just holding hands with Pepper, they don't mention it.

If any of them hear the occasional crashing and smashing and roaring from upstairs, or notice the steady stream of mattress deliveries, they don't mention that either.

-

"What's it like?" Tony breathes, as Bruce's eyes start to change and his skin starts to lose its pink. "What's it like, right now? What does it feel like?" He speeds his hand up for a few strokes, then slows it right down again, keeping his grip tight but not giving Bruce quite what he needs.

"What," Bruce gasps, "are you fishing for? It feels great, just go faster."

Tony laughs, presses a kiss to Bruce's nipple. "No, no, I mean – the Hulk part. You're green right now, did you even know that? You start going green really early in the process."

"Do I?" Bruce lifts an arm and looks down at himself. "I'm not that green."

"You should see your eyes." Tony bends down and kisses Bruce's mouth, lush and wet. "What's it feel like?" he repeats, against Bruce's lips. Tony gives his cock a little extra squeeze to punctuate the question.

"Good," Bruce growls, and his voice is lower than normal, not quite as deep as the other guy, but getting there. Tony eases back, makes his touch light, teasing. The green fades. Tony grins.

"It's so much fun to have sex with you, you come with your own little orgasm-meter." Now he takes his hand off of Bruce's cock entirely and starts roaming elsewhere, stroking his thighs, kissing his soft belly, running his fingers through his chest hair. Bruce's eyes stay somewhere between brown and bright green as he watches Tony carefully.

"You're not gonna let me, are you," he sighs.

Tony shimmies downward and places a sucking kiss on Bruce's inner thigh. "Tell me how it feels."

Bruce sits up on his elbows. "You really want to know?" The question is genuine, surprised.

Tony strokes a slow thumb over Bruce's left knee, doesn't meet his eyes. "I always want to know."

A few seconds tick by, the room going still around them as Tony waits for Bruce to say it. "What I don't tell people," Bruce says slowly, voice low, "what I never tell anyone, is how good it feels to change into him." He licks his lips. "Even when I don't want to."

Tony takes Bruce's balls in his hand, caresses them gently. Rubs a thumb against the crease where they meet his body. Tries not to talk.

"It's like I – let go of myself," Bruce says. "Like flying, like the, the Hulk is always straining upwards and I cut the tethers, one by one – oh, that's nice, keep doing that."

There's a definite increase in green, but Tony hasn't controlled all the variables and can't tell whether it's a physical response to what Tony's doing or an emotional response to what Bruce is saying. He does as Bruce says, keeps rubbing gently, then brings his other hand up to wrap loosely around Bruce's cock again, stopping momentarily to get more lube.

"So it's like orgasm," Tony offers. When he looks up Bruce is shaking his head, eyes flashing a strange hazel under dark messy hair.

"Not at all. And sort of. It's like – have you ever done acid?"

"No, I treat my body like a temple."

Bruce laughs. "Well, it's like that, with all the fear and freaking out and getting unstuck in time." Bruce arches forward into Tony's hands, starts thrusting through Tony's tightening fist. Greener, greener, greener.

"But good."

"But good," Bruce agrees. "Like raw – raw sensation. Oh, fuck, Tony – "

"That's what we're working up to," Tony agrees, and takes his hands off Bruce's dick again, moves to lie full-length on top of him instead. Bruce groans, tries to fuck up against Tony's body, but he doesn't have the right angle or the right leverage.

"What?" Bruce pants, and meets Tony's eyes. "What did you say?"

Tony ignores the question. "Can you do it slow? Like, if you're cutting the tethers, can you cut them slowly?" He lifts his hips to keep Bruce from getting the friction he needs.

"Tony, come on – "

"No way. Tell me first." Tony grins down at him, teasing, and then Bruce's eyes flash all the way green and the world is spinning around Tony as Bruce rolls him over, gets on top and holds him down.

"Yes," Bruce says, and his grip on Tony's wrists is deceptively light and easy, because Tony can tell there's already more than human strength there. "I'm pretty sure I can." He leans down and kisses Tony hard, grinds his cock down against him, rubs himself against Tony's body like he's scratching an itch. Using him. It feels amazing.

When he pulls back Tony's breathing fast and his dick is hard. For a moment neither of them moves, and then Tony surges upwards, resisting Bruce's grip as much as he can, kissing and biting his mouth, thrusting helplessly upwards, trying to get some friction. He doesn't try to get away, or to get back on top.

Bruce grabs Tony up and rolls them back over, maybe recognizing that Tony isn't the kind of guy to lose in a game of chicken, even when playing against a thousand-pound radiation monster who would crush him to death in two seconds flat if Tony were still under Bruce when he changed.

"Show me," Tony pants, "show me, show me, do it slow, I want to see – "

Green flushes up Bruce's body like a blush, like a rash, coating him in green, covering him, but his body doesn't start to shift right away; instead he's just Bruce-but-green, grinding up against Tony while Tony grinds down against him. A violent grin splits Bruce's face. His canines already look square, blunt.

"You're gonna like this," he grunts, in that low almost-Hulk voice. "Hold on."

And then it's slow, so slow: Bruce's muscles expanding and contracting, his bones starting to shift and then popping back into place, his body swelling inch by inch, bit by bit until Tony can't help but touch, can't help but put his hands on the planes of muscle, the ridges of bone, the shifting lines of Bruce's face; can't help but squeeze and stroke and scratch while Bruce thickens and stretches to fill his hands. A sound starts to emerge from this throat, like a whine, like a scream, but still muted and restrained.

"Easy," he hears himself muttering, "easy, easy, easy," in a soothing tone, the way he might try to calm an animal, "easy, Bruce, easy, just like that, you're doing so good, oh god you're so good – "

He's maybe halfway there, body shifting and twisting in slow-motion, rippling like water to fill empty space. His breathing is still ruthlessly controlled; he keeps taking slow, deep breaths even as his lungs and chest expand, even as his new muscles must be crying out for oxygen.

Tony grins wildly and takes both their cocks in hand, rubs them together while Bruce grows and grows against him. Just the sight of it is overwhelming, the way Bruce's dick gets bigger, thicker, hotter, rougher to the touch as Tony fucks himself sore against it. Now Bruce's breath starts to come faster, deep breaths turning to fast panting hyperventilation, and Tony grips harder, jerks faster, finally giving Bruce all he's got.

"Tony," he gasps, "I can't, I can't – "

"Yeah," Tony breathes. "Yeah, yeah, c'mon."

Bruce lets out a low groan and throws his head back and arches his back and expands, his whole body just flowing outward smoothly. He thrusts up once, hard, against Tony, who's already coming helplessly, then comes himself a second later, the instant he's fully Hulked.

When his eyes are able to process visual information again Tony collapses down onto the Hulk's chest. The great thing about having the Hulk for a bed partner is that you can't squish him; of course, Tony thinks, the downside is that he can easily squish you. Absently, Tony presses a soft kiss to the corner of the Hulk's broad mouth.

"That was amazing, buddy," he sighs. The Hulk doesn't move for a minute, but then, delicately, pats Tony's back.

-

Tony strolls into Bruce's lab one day to find him playing what can only be described – and will be described, if they ever get onto the internet – as Avengers sex videos.

"Whoa, sorry, am I interrupting a private moment?" Tony throws his hands up, taking a step back. He doesn't take his eyes from the screen, though, which is playing footage of the Hulk bracing his broad palms over Tony's ribs.

Bruce just smiles at him benignly over his glasses. "I'm compiling data."

"Is that what the young scientists are calling it these days."

"I could use your help, actually. My memories from when I'm the other guy aren't very good, and JARVIS's sensors can only tell me so much."

Tony blinks. "You – you had JARVIS take readings of us while we were having sex?" In retrospect, Tony kind of can't believe he's never done that himself. Video, sure, but – he glances over Bruce's shoulder at the other screens – infrared? Radiation levels? Heartbeats, blood pressure, enzyme levels . . . "This is amazing," Tony says, pulling up a stool and settling in beside Bruce.

"Well, this is why we've been having all the hot awesome monster sex, right? To gather data?"

Tony manages to tear his gaze away from the screen. Bruce is grinning at him sidelong. "Yes, Dr Banner," Tony says seriously. "That's definitely the reason."

Standing up again he backs Bruce up against the edge of the table, takes his mouth in a hot, bruising kiss. Bruce bites at his lips, wraps a broad palm around the back of Tony's neck and squeezes tightly, holding him in place.

As Tony breaks free and kisses and bites his way down Bruce's neck, Bruce sighs.

"I'll let you have first author."

"That's so hot," Tony mutters into the hollow of Bruce's throat. "But it's only right, since I did all the glamorous sexy field work and you're in here crunching the numbers."

Bruce laughs, the sound vibrating against Tony's lips. "You remind me of this professor I had at Cambridge." His voice is just a little bit Hulked, and Tony knows that nothing's really going to happen here in the lab in the middle of the afternoon, but it still sends a shiver down his spine and a jolt through his batteries every time Bruce lets a bit of the other guy slip through.

"Oh really."

"Yeah," Bruce breathes. He cocks his head, apparently considering something, and Tony waits; Bruce's ideas are usually worth waiting for.

He doesn't have to wait long. Bruce pushes away from the table, turns Tony around to reverse their positions, and braces his hands against Tony's hips as he drops to his knees.

"Must've been some professor," Tony offers. "What'd he teach?"

"Australian art history," Bruce murmurs, his quick hands making short work of Tony's button and zipper. Tony can't help but laugh, settling his hands on Bruce's shoulders as Bruce wraps a gentle human fist around his cock.

Bruce sucks gently at the tip, just for a few seconds, then pulls off. "Actually, he was my supervisor for my undergraduate project in biology." Another slow, easy suck. His glasses slip down his nose a little. "But I did take Australian art history." Now he sucks a little harder, takes more of Tony's cock into his mouth, and Tony fights to catch his breath.

Behind him, the light from the monitor flashes and changes; their sex video is still playing behind him, with the sound off.

"So are you gonna attach these instructional videos to the – oh, fuck – article we're apparently publishing? Give the world of radiation physics a thrill?"

Bruce hums around Tony's dick, amused, then pulls back again. Sometimes Tony wishes he were constitutionally capable of not talking, at least long enough to stop asking questions during a blowjob. "I thought we'd write around the sex parts, actually," Bruce grins. His mouth is red and wet, his skin flushed pink for once. Tony runs a finger along his jaw.

"You're such a prude," he says affectionately. "I'll have you know there are tons of sex videos of me on the internet – "

"I already knew that."

" – and they haven't affected my scientific reputation one bit."

Bruce grins, jacks Tony's cock slowly with his hand. "Fine, you get the Hulk to sign the consent form."

Tony starts to laugh, then changes to a breathy moan as Bruce sucks him again, now with one hand around the base of Tony's cock and another braced on Tony's hip, squeezing his thigh maybe hard enough to bruise; maybe as hard as Bruce is capable of squeezing.

"I think somewhere small but prestigious for our first co-authored publication," Tony muses, as Bruce's head begins to bob up and down on Tony's cock. His messy salt and pepper hair is in his eyes and his glasses are perched delicately halfway down his nose and it's like every sexy professor fantasy Tony's ever had. "Lots of attention without having to be too showy."

Bruce gives him a thumbs up, and Tony laughs again, keeps talking. "We can call it something totally academic and boring, and no one will know that it's – oh – oh, yeah – "

The sucking stops, and Tony looks down at Bruce, who's pulled his mouth off and is jacking his cock with one hand. "No one will know what?" he asks, and his eyes are dark.

Tony squeezes his shoulder. "No one will know that it's secretly our celebrity sex tapes," he grins, and thrusts into the hot tight circle of Bruce's fist. "That every experiment ended with you coming all over me." Bruce jerks faster. "That all the data was gathered while I jerked you and sucked you and you tore the shit out of the furnishings – " Tony stops, amazed, as Bruce's eyes slip closed and he falls forward, resting his forehead against Tony's hip.

"Suck me," Tony breathes, and Bruce shifts wordlessly and gets his mouth on Tony's cock again. Tony's so close now, his whole body just shaking with need. He pets Bruce's shoulders, his neck, touches a finger to his lips, grabs his hair, just touches him, as much of him as he can get his hands on.

"This is going to work," Tony murmurs, amazed.

Bruce moans around his dick and then swallows him, just swallows him right down, and Tony comes helplessly down his throat, in his mouth, knees almost buckling, held up by Bruce's solid broad shoulders under his palms.

When he's done Tony collapses down to the floor next to him, kisses him wet and dirty.

"You wanna go to one of the less frequented bedrooms with the sturdier beds and let me return the favor?" Tony asks.

"No, no, I'll be okay, I just – maybe don't touch me for a second," Bruce says, not making eye contact.

"You sure?"

"Yeah, the transformation knocks me out pretty hard sometimes, and I have stuff I wanted to finish today." He waves upward vaguely at the computer screens where, presumably, their sex tapes are still playing. Tony's really glad he blocked off this suite of labs for Bruce's private use.

"Ah, science over sex. I've made that decision many times myself." Leaning against Bruce, he lifts his hips and does up his fly. "Though really it's best when you can combine them. I remember one time – " An idea strikes him. "Uh, will you be okay here? Do you need any," he waves his hands in Bruce's general direction, "aftercare?"

Bruce chuckles. "No, I'm fine. Why?"

"Because I suddenly really need to go to the polymer lab," Tony says, jumping up. He starts to leave, then runs back to lean down and kiss Bruce one more time, then dashes away again. He can hear Bruce laughing as he goes, and grins to himself.

-

Pepper comes down to the polymer lab the next day to find him, and laughs when she sees the long row of pneumatic actuators powering large metal cylinders back and forth in a linear motion. She laughs again when she sees the materials covering each cylinder. Tony waggles his eyebrows from behind his protective goggles.

"What's up?" he shouts, over the noise of the machines.

"I came down to see what you were up to, but I think I can guess," Pepper shouts back. "Fury's on the line, something about killer cyborgs."

"Doombots?" Tony asks, shutting down the machines.

"No, something else."

Before he gets to it, #12 gives off a noise like a tire exploding and bits of plasticy film fly everywhere.

"JARVIS, scratch twelve," Tony calls out.

"Of course, sir. Shall I prepare the Mark VIII?"

"Yup, I guess." He turns off the last of the actuators and tosses his goggles onto the workbench. "What else did Fury say?"

"Just to be sure to bring Bruce," Pepper says. "I've sent Celia up to fetch him."

"Good good good," Tony says, racing into the elevator. Pepper rides with him down to the sub-level where the Mark VIII is, since it's not ready for self-deployment yet.

There's a long pause. Tony watches the floors tick away on the elevator display.

"So, you must really like Bruce, huh?" Pepper teases, after a minute.

Tony waves her off, scowling. "Shut up."

"No, no, I feel offended, you've never created any new polymers for me – "

"Yeah, well, you don't have a dick that can tear through masonry."

She nods solemnly. "More's the pity."

-

It takes Tony another week or so to finish the new material, partially because of various spates of cyborg interruptions, and partially because he's not actually a chemist or whatever, but anyway once it is done it's probably going to revolutionize some field or other, which is nice. Also it should work for its intended purpose, which is even nicer.

"I got you something," he tells Bruce, who looks up from the sandwich he's munching and the numbers he's crunching to raise his eyebrows at Tony.

"Yeah?" he sounds cautious. Tony, impatient, hands him the box.

"Open it, open it."

Bruce raises an eyebrow and complies, tearing off the bow and the wrapping paper and flipping up the velvet lid of the jewelry box. "It's . . . a condom?"

Tony bounces. "I invented you a polymer," he says. "I had, uh, concerns? About the Hulk's high-friction superskin. But I didn't want that to stop me from living the dream, so, ta-da! It absorbs force on the inside, sort of like vibranium, but on a smaller scale, obviously, it doesn't absorb everything. And the outside is skin-safe and slick and soft, see? Plus it's rated for your level of, ahem, force, it won't break, I tested it myself. Well. I didn't test it myself, obviously, I built machines to test it, calibrated to, to – uh." Tony stops talking, because Bruce is smiling at him like he doesn't want to but can't help himself, and it does something disastrous to Tony's train of thought.

"You want me to fuck you with this," Bruce says, his voice so soft and uninflected that Tony can't even begin to get a read on him.

"Yeah." Tony swallows. "If you like, you know, whatever – "

Bruce grabs him and kisses him, hard, then pushes him up against the wall and kisses him again, and again, and when he finally pulls back and stops his eyes are already bright green.

"Give me a couple days to think about it," Bruce pants, and leaves Tony alone in the lab.

-

Bruce avoids him for five days, and Tony paces his labs and freaks out a little and invents two or three patentable things and lets Bruce avoid him. Pepper's out of town again, London this time, so Tony can't even go downstairs and annoy her into placating him, which is probably for the best in terms of their relationship, but he still wishes she were there. He considers flying to London to interrupt her meetings, but compromises and sends her roughly two hundred text messages instead. She replies to about one out of ten, which means she's sympathetic and not too pissed off, and probably also means that her meetings are really boring, even to Pepper, who likes meetings.

Her replies are all basically the same, though, variations on a theme. calm down. give him time. it'll be okay. you can wait.

Tony waits. He forces Steve to watch all the Star Wars and Alien movies, even the shitty ones, which Steve does with good humor, nodding along to Tony's explanations of Death Star physics. He drags Clint down to the archery range and takes some high-speed camera footage, makes Clint explain everything about arrow trajectories and wind resistance until Tony has what he needs to design better, cooler arrows. He even asks Natasha to spar with him, which gets him a disbelieving look and a pat on the back. "That's a terrible idea," Natasha says, "but let's go get some smoothies, okay?" It turns out Natasha makes really good smoothies.

Thor actually notices his twitchy moping and offers to get Tony drunk, which Tony takes him up on. The resulting property damage isn't too bad, and Tony should be able to hide it from Pepper as long as he can get the contractors in to fix it before she's back from London.

When Bruce stops avoiding him, he does it all at once, coming into Tony's workshop at night and plunking himself down on the couch behind the bench Tony's working at.

"I don't want to hurt you," he sighs. Tony minimizes his project – it's his and Bruce's Hulk project, actually – and goes over to sit next to him.

"Yes, you do." Bruce looks up at him sharply, so Tony continues, "you do, and I want you to."

"Yeah, that doesn't make it any easier." Bruce scrubs a hand through his hair.

"It should. Look, you have all the data. It's all right there in the project file. The Hulk isn't out of control and hasn't been for a long time. So there's no problem."

"Yeah, it seems that way, but – "

"It is that way."

" – it seems that way, but all it takes is one wrong move, and he could – I could – "

"Bruce," Tony says quellingly, and Bruce is, momentarily, quelled. "If you really believed that, we wouldn't have gotten this far in the first place. And you wouldn't be here right now."

Bruce nods, conceding the point.

"Do I have to give you the do it for science speech again?"

"No," Bruce sighs. "It worked the first time."

"Thought so."

"Plus of course I was convinced by your raw sexual magnetism, I don't want to overplay the science experiment aspect of it."

"Great." Tony pats his hand. "Let's go put your dick in my ass."

-

It actually takes them a while to work up to it, though; that night they're both kind of on edge and Bruce goes really green really quickly, so they end up sticking to their established routine after all. The next night there's an alien invasion, just a little one but with very annoying sneaky aliens, so it ends up taking the better part of the following week to chase all the aliens down and round them up. After they find the last one and send it back to its dimension Thor decides to throw a party – at Stark Tower, of course, where Thor throws all his parties – to celebrate their mighty victory. Bruce gets adorably smashed, and Tony's fairly tipsy himself, or at least tipsy enough not to notice right away when Bruce starts making out with him sloppily in a darkened corner of the room.

"Bruce Banner," Tony says, emphatically, holding Bruce by the shoulders. "Bruce, Dr Banner, it is totally okay if you don't want to fuck me."

Bruce smiles. "Yeah?"

"Yeah. You absolutely do not have to fuck me. We can still hang out and do science and have hot monster handjobs on very sturdy steel-reinforced beds."

"That would be an elegant solution if I indeed did not want to fuck you."

"Wouldn't it?"

Bruce kisses him again, still sloppy but passionate, too, in the way he doesn't usually allow himself to get. "We'll have to come up with something else," Bruce breathes. "I can come up with something else, I have two PhDs."

Tony looks up from where he was sucking on Bruce's neck and stares him in the eye. "I did not know that. How did I not know that. Two PhDs? What was your second dissertation on?"

"W boson helicity fractions in top-quark decays."

"Fuck you're a stud. C'mere." Tony kisses him again, missing his mouth at first, but finding his way there eventually.

Just then Steve passes by their little alcove and does a double-take. "Are you two – ah – oh. Um."

"Definitely," Clint says. Tony glances over his shoulder and sees him sitting with Natasha on the back of the couch, both of them staring avidly and passing a bag of popcorn back and forth.

"Definitely 'ah-oh-um'-ing each other," Natasha agrees, mouth full of popcorn.

"Ah, victory sex!" Thor booms, coming out of the kitchen. He's wearing a chef's hat and an apron. "Shall we make it an orgy?"

-

They don't make it an orgy, though Tony does suspect that something might be going down with Natasha and Steve, or possibly Thor and Steve, or Clint and Thor and Natasha, or maybe Natasha and Thor. Tony's not sure. They're all super hot. And Tony's actually quite drunk.

He and Bruce leave the party area sometime after three in the morning, when the karaoke has moved on from Thor and Clint's pop-diva duets to Natasha's smoky Joan Jett covers. They make it back to Tony's floor of the tower with little incident – he's proud of his ability to drive the elevator while drunk, even if it does only go in two directions – and stumble out towards the bedrooms.

"Hey, hey," Tony says. "Come sleep with me."

Bruce looks at him fuzzily. "That's what I'm trying to do," he protests softly.

"No, in my bed." They've trashed a number of the guest bedrooms, many of them more than once, but Tony's pretty sure he's never had Bruce in his actual bedroom before. He likes that bed. He grabs Bruce's hand and pulls him along.

"Too fast, too fast," Bruce says mournfully. "If I trip and stub my toe and Hulk out it'll be your fault."

"I'll accept the consequences," Tony grins, pushing him into the bedroom. "Hey, you said Hulk out."

"I did," Bruce agrees.

"Now, there's one rule in this bedroom: don't turn into a monster in the middle of the night and trash the place." Tony considers. "And no fishhooking."

Bruce nods seriously. "Got it."

They get naked and crawl under the cool, clean sheets together. Bruce, to Tony's surprise, curls up next to him immediately, putting his head on Tony's shoulder and his arm over Tony's waist. Tony hesitates, then wraps an arm around him.

"This is nice," Bruce says, drooling a little against Tony's bare chest.

"Yup."

There's a long silence, and Tony is almost asleep when Bruce speaks again and startles him back awake.

"I just never thought I would want to be him. The Hulk. I never thought I would turn into him willingly. I always thought I needed a cure."

Tony tries to think of something to say to that, but it's too late and he's too drunk to come up with something pithy, and he hates being sincere.

"It's just a lot to get used to," Bruce sighs into the dark. "My life was profoundly different six months ago."

"Yeah," Tony says, finally. "Mine too."

-

It ends up happening after a battle, the kind where Tony (and the Mark VIII) get the shit beat out of them and Bruce spends the whole time locked in a lab designing a compound to repel mutant bears. When they meet up afterwards, Bruce is uncharacteristically tense, twitchy even, running his hand through his hair and bouncing on the balls of his feet.

"You okay there?" Tony asks, walking into the lab. "Did you have coffee?" Bruce turns toward him immediately.

"Hey," he says. "Let's fuck."

Tony raises his eyebrows. "Okay?"

Bruce hustles him out of the lab, into the nearest approved-for-the-Hulk bedroom, and doesn't waste any time in getting them naked. His hands are hot and fast, tearing at Tony's clothes, and then he gets his mouth on Tony's skin, placing a trail of sucking kisses over Tony's collarbones, his neck, edging around his arc reactor.

"Didn't like being left out, did we?" Tony laughs. "Give you a few months of regular Hulk Outs and you start to get tetchy if the rest of us go off without you."

"It's not that." Bruce is stripping off Tony's clothes, manhandling him around the room, not green yet but acting like it.

"No?" Tony braces his hands on the footboard of the bed and groans appreciatively when Bruce gets one lube-slick finger inside him.

"All the fighting, the – I could see you all on the monitors in the lab," Bruce says. His cock is hard against Tony's ass. "Fighting, and he – " Bruce stops for a second, takes a deep breath. "I wanted so bad to just, just let go, do some damage. I wanted to be him, but I had to be me, and I had to focus on the problem, and do science, and it was torture."

Two fingers in Tony's ass now, moving rough and fast against him, and while Tony would normally be all for that he gets the sense that Bruce is going to need to find his calm again if this is going to work, if it's going to go where he thinks it's going.

"Hey," he says, "Bruce. Hey. Slower."

Another shaky breath, and Bruce slows down, one broad palm coming to rest in the small of Tony's back. "Sorry," he says, "sorry, I – "

"Don't be sorry, just do it slow. Hey." Tony looks over his shoulder. "It's going to happen, I'm here, we're doing this. Slow down."

"Right."

Bruce backs away, taking his fingers out of Tony's ass.

"Well, maybe not that slow," Tony says, and Bruce laughs behind him.

"Get on the bed."

"On my back or my front?"

"On your back."

"Hmmm," Tony smiles, lying down.

Bruce takes his time coming to kneel beside him. He's hard, but, Tony's surprised to notice, not green at all. He's taking deep, even breaths.

"JARVIS, are you getting this?" Tony asks.

"Indeed, sir. Dr Banner has asked me to do enhanced data collection on all of your intimate encounters. Should I suspend?"

"No no, keep recording." Tony licks his lips as Bruce runs a slow, steady hand up Tony's calf to his knee. Still not green. "Actually, JARVIS, what's Dr Banner's gamma output right now? Is he – ow!"

Tony breaks off as Bruce pinches his inner thigh. "We analyze the data later," Bruce says. "We generate the data now. Pay attention."

"You keep pinching me like that, you'll have my attention," Tony pants. Bruce stares at him for a long moment, then pinches him again, harder. Hard enough to bruise.

"You like that?" Bruce asks, voice low.

"Pretty much," Tony gasps, his cock leaking against his belly. "Do it again."

Bruce pinches him some more, leaving little tiny red marks that'll black up later. Tony hopes to god that he doesn't get any other bruises on top of them; these ones he wants to keep. After a minute Bruce bends his head and sucks on the soft sensitive flesh of Tony's thigh, drawing it in to his mouth and biting hard, sending a bright flare of pain shooting through Tony's body. He slips his fingers into Tony's ass again, and he's still going fast and hard but now Tony knows that the roughness is deliberate, that Bruce is in control of it.

"Yeah," Tony gasps, spreading his legs a little wider. "Just like that."

Bruce starts up a hard rhythm with his fingers, sucking and biting his way up Tony's hip to suck his cock, once, with just a hint of teeth.

"You wanna come now, or you wanna come when the Hulk fucks you?" Bruce asks. Tony doesn't even have to think about it.

"I want to come when you fuck me," he replies, and Bruce nods. Shoves in a third finger, and god, it already feels like a lot, three big fingers holding him open, but it's still only the pre-show before the opening act, and they've got a ways to go.

"Good." Bruce reaches down to the floor with his free hand to find his pants, manages to liberate his wallet from his pocket and the condom from his wallet.

"Aw, you were keeping it in your wallet? That's so – ungh – sweet."

Bruce's skin shivers with green for a second while he rolls the condom on, and then he settles down into pink again. "Oh, this is weird," he says.

"What's it feel like?" Tony sits up a little, curious, and Bruce shoves him back down onto his back.

"It kind of – dulls sensation a bit," he says. "You could market these."

Tony laughs, groans as Bruce takes up his steady rough thrusts again. "Yeah, for five hundred thousand dollars a pop you can not have to worry about coming too fast. They'll sell like hot cakes."

Bruce laughs with him, bends over him to kiss his mouth. "It's a pretty amazing material, though," he murmurs. "You must have some applications for it." He takes his fingers out of Tony and lines up his cock, pushing into him slow and hard. Tony gasps.

"Oh! oh, god, yeah, I mean, no. That's what Development's for, I sent it off to them last week. Here you go kids, have an ultra-light ultra-thin expandable impermeable skin-safe material that – fuck, fuck, fuck, yes –" Tony takes a second to find his train of thought again, " – that absorbs force on one side and is, is soft on the other. R-revolutionize something."

Now Bruce is all the way in, rocking against Tony and pressing his face against Tony's knee, biting a little like he can't stop now he's started.

"I won't tell you what I used it for, but I will say water-based lubricants only," Bruce grins, short of breath.

"Ha, oh, god, don't make me laugh, I'll come – "

Bruce stops teasing and bites hard on the tender skin at Tony's knee, focusing him on the hot flare of pain, calming him down. Tony shudders and gets back on track, lifting his hips to meet Bruce's thrusts.

"Let me know when you're ready for more," Bruce says, and now his eyes are finally getting green. Tony meets his gaze.

"Anytime," he says. "You want me on top?"

"Not – not yet," Bruce says, and stops moving for a second while he takes a breath. "I can take it." A jolt of pleasure shoots through Tony at that, at the knowledge that the only thing keeping him alive and uncrushed right now is Bruce's will not to change. He rubs Bruce's shoulders with his hands, just to touch him, to feel the restraint singing in his muscles and the shivering thread of control that holds him together.

Tightening his legs around Bruce's shoulders, he pulls himself up onto Bruce's cock and then collapses back down. Bruce shudders.

"Give me more," Tony breathes. Bruce's skin flushes suddenly green and he does, thickening inside Tony's body, stretching him out just a little further.

"Yes, yes, yes." Tony struggles to catch his breath. "More, do it again – "

"Greedy," Bruce chuckles, voice getting low. He breathes out and his grip tightens painfully on Tony's legs and then he moans as he expands again, his cock growing inside Tony's ass. Tony arches his back and he thinks he's coming for a second, the sensation is so intense, but then his cock is still hard, pressed desperate against his belly.

Bruce bends and mouths Tony's nipple, bites at his neck, rubs his big palms against Tony's sides; he's almost unbearably heavy now, pushing Tony down into the mattress.

"You're amazing," Bruce says. "You feel so good." He gives a long, slow thrust, out and then back in, casual but rough and almost too hard to take, just the right side of painful. "Get on top of me."

When they roll over Bruce slips out, and Tony gasps at the sensation of emptiness. He straddles Bruce's lap immediately and gets Bruce's cock back inside him, wincing as he slides down onto it.

"Oh, oh, wait," Tony says, trying to adjust. He takes a deep breath. He's never been this full before, and they're not done yet, not quite. Bruce stills, his hands squeezing Tony's hips hard, leaving big finger-shaped bruises in their wake.

"Okay," Tony says a second later. "Okay, let me do the work, I got this." He grits his teeth and starts raising and lowering himself on Bruce's dick, riding him as hard as he can. Tony feels himself opening a little further on each thrust, taking a little more, until he's sliding up and down easily, quickly, every stroke a hot wave of sensation, setting off chain reactions all through his body, pleasure and pain zinging along his nerves.

"Can you – Tony, god, god, can you take more, I need – "

"Yeah, yeah, yeah, give it to me, c'mon. Get bigger. I want it. Get bigger inside me."

Bruce's eyes close and his head turns to the side as he lets out a long slow cry of pleasure, as he puts on more muscle and more weight and fills Tony up, stretches him out, forces him to take it.

"Almost there," Tony gasps, riding him hard now, fucking him, lifting himself up and down fast on the Hulk's cock. "Come on, I can take it, give me the – fuck! – give me the rest."

And now Bruce is screaming his way to the Hulk and Tony cries out too, stretched wide and aching and full and perfect, the thick hard force of the Hulk's cock splitting him open, holding him wide open. He takes it, takes every inch of it, lets it fill all the space inside him and turn him inside out.

"Jesus, fuck," Tony grits out. He tries to lever himself up and can't, tries to thrust but can't; he's got no leverage, and he's completely at the Hulk's mercy.

The Hulk just grins and runs his hands over Tony's body, knocking Tony around a bit but being careful, then settles them under Tony's thighs, holding him up enough to get a little purchase. Tony takes a few quick breaths and then rocks his body forward as best he can, shoving his weight against the Hulk and rubbing himself back and forth on the Hulk's dick. Beneath him the Hulk growls, rippling the air around them.

Tony wraps a fist around his cock and starts to pump himself in counterpoint to the shifting shallow thrusts of the Hulk's cock. His whole body is trembling now with exertion and pleasure, his skin running hot and cold and his ass trying to clench around the hard length inside him. Tony lets his head fall back and fucks helplessly, fucks his hand and fucks himself on the Hulk's dick, eyes slipping closed. He hears the Hulk roar beneath him and feels the Hulk's cock twitch inside his ass; Tony gasps for air and digs his fingernails against the Hulk's thighs and when he comes it's like his whole body is coming, the sensation rushing through every single cell, white hot joy overwhelming him for endless seconds.

It takes a little while for Tony to come back to himself, and when he does he feels Bruce already getting smaller beneath him, shrinking and softening inside him. Tony tries to catch his breath as Bruce blinks up at him, mouth red and slack.

"Hey," Tony tries to say, but his voice is hoarse and his throat is dry and it comes out as a dull croak. He swallows and tries again. "Hey."

"Hey," Bruce says. He looks utterly exhausted and utterly satisfied. He runs his hands – soft broad palms – up and down Tony's sides, almost absently.

Tony wipes his forehead with the back of his arm. A smile breaks over his face, he can't help it, and a few seconds later he's grinning down at Bruce, who's grinning up at him. Tony bends down as best he can and kisses Bruce's neck, his chin, stretches up to meet his mouth in a slow kiss.

-

They find a shower and a bed – both as close to where they are as possible, since Tony's going to have some trouble walking for a while – and sleep for something like twelve hours straight, which is almost twice as long as Tony's ever slept without being pass-out drunk first. But it was a long day, what with the mutant bears and then the monster cock in his ass, so he can probably be forgiven. When they wake up – it may or may not be morning – Bruce makes them pancakes, and Tony hobbles down to the kitchen to eat them.

As they're sitting down Pepper walks in, dressed for work in a perfectly tailored dove-grey suit, but Tony can't tell if she's just about to start the day or just finishing; the sunlight coming in the windows could be either sunrise or sunset, and the oven clock reads 7:23 – no help.

"Hi," Bruce says, holding out a chair for her next to Tony. "Want some pancakes?"

"Love some," Pepper says. Bruce flips the last batch and sets the plate of them on the table. It's piled high, the pancakes uniformly perfect and golden-brown. Tony's stomach actually rumbles.

Bruce sits down on Tony's left and takes some pancakes for himself before Tony's fork can reach the plate.

"Hey," Tony protests.

"I cooked, I get first pick," Bruce says, poking Tony's hand with his butter knife. Tony pokes him back with his fork.

"Pepper?" Bruce offers the plate of pancakes across the table. Tony glares at him, and Pepper laughs.

"Thanks," she says, grabbing two off the stack so that Tony can finally score some pancakes of his own. They all dig in, and Pepper tells them cheerfully about the fate of Tony's condom polymer.

"Basically it's all applications too boring to care about," Pepper says, chewing thoughtfully, "but which will all make the company plenty of money, so that's nice. Unfortunately I couldn't convince the nice people in Development to mass-produce them as Hulk-proof prophylactics."

"I still say you're missing out on a goldmine," Tony sighs. "Imagine all the smarmy assholes who'll claim they just really need the extra-strength Hulk-sized ones. We'd make a fortune and it would be purely at the expense of complete dickweeds."

"Your favourite way to make money," Pepper nods. "I agree that it would be a noble addition to the Stark line of Avengers-branded merchandise that we're rolling out, but for some reason I don't think the board would go along with it. Not to mention SHIELD PR."

"It's just sad to see such a beautiful invention perverted from its intended purpose," Tony sighs.

"You can always make them for me," Bruce offers. He's loading neat squares of syrup-drenched pancake into his mouth with his left hand, and with his right he's scribbling something in a notebook.

"Unfortunately they're reusable; you can just, uh, empty them out and boil them and they return to their original shape."

"Really." Bruce blinks at him. Tony shrugs. "Huh." And he goes back to writing in his notebook.

"What are you working on, Bruce?" Pepper asks, wrapping her hands around a hot mug of coffee. Probably it's morning, then; Pepper doesn't usually drink coffee at night.

Bruce speaks around a mouthful of pancake. "Oh, just this article Tony and I are putting together."

"What? Give me that," Tony says, and grabs at the notebook. There's a brief struggle during which Bruce's pen gets dropped into the pool of syrup on his plate, but Tony emerges victorious.

"I was working," Bruce mourns.

"Hush, I want to see." He looks it over. "You're writing the abstract? I wanted to write the abstract!"

"What's it about?" Pepper asks. Tony grins, and Bruce blushes, and the combination of the two makes Pepper raise an eyebrow.

"Well, according to this, we used a variety of testing methodologies to – "

"It's a sex chronicle," Bruce interrupts, sighing. "It's about how sex influences the Hulk's gamma transitions."

"Except we are endeavoring not to mention the Hulk or sex," Tony adds.

"Sounds simple enough," Pepper grins. "Be sure to let me know how that goes." She wipes her mouth with a napkin and stands up to leave. "Tony, we have that benefit for the Women in STEM Fields scholarship fund, don't forget."

"I am not sure that I will be able to stand up straight long enough to give a speech," Tony says, wincing. "I'm sitting on a cushion right now."

"Lucky for you I'm giving the speech," Pepper says, and kisses him on the top of the head. "You can bring your cushion with you. I'll just tell everyone you have hemorrhoids."

"I think I would be more comfortable with you telling them I take it up the ass from the Hulk instead," he says, turning in her grasp to kiss her when she leans down to meet him.

"Whatever you like," she agrees. "Just have your cushion ready at eight."

"I will definitely be ready," Tony agrees firmly.

"I'll make sure he's ready," Bruce offers, smiling.

"Thank you, Bruce," Pepper says, and kisses him on top of the head too. Bruce kind of ducks his head and grins like a kid, which Tony cannot help but find entirely adorable.

When Pepper's gone, Bruce holds out his hand for his notebook, and Tony hands it over, sighing.

"So," Tony says. "We used a variety of testing methodologies . . . "

Bruce pushes his glasses up his nose and reads. "We used a variety of testing methodologies to determine the best – "

"Sexiest." Tony grins at Bruce, and Bruce chuckles.

"To determine the sexiest, that's true, method of inducing isomeric transitions in gamma-irradiated subjects."

"See figure one, giant green rage monster." Tony leans in close, sucks at the soft skin behind Bruce's ear. Bruce shivers.

"Giant green sex monster," he corrects. His hand wanders over Tony's chest, drawing slow circles around the arc reactor.

"That too."

"Researchers used biodosimetric analysis to measure – "

"Researchers?" Tony repeats, drawing back a little. "You mean me."

"I'm a researcher too, asshole."

"You weren't there for half the testing! Frankly I think you abandoned me throughout the experimentation process."

"The Hulk was there. He can be a researcher. Stark, A.E., Banner, R. Bruce, and Hulk, T."

Tony laughs, captures Bruce's mouth with his, kissing slow and syrup-sticky.

"You're still going to give me first author, huh?"

"Of course," Bruce replies calmly. "It was all your idea."