Chuck's most secret and most shameful fantasies have always been about Ellie. He's not sure where they come from - maybe it's only natural, considering how close he and his sister had to become to make it after their parents left. Maybe it messed Chuck up that the only male influences available to him while he was forming a sexual identity were Harrison Ford movies, Morgan, and Mr. Thornton, the junior high health teacher. Ellie has this Carrie Fischer-quality that would have confused any pubescent boy, Chuck is sure, in his position; Morgan thought that Ellie was sex for a majority of his pre-adult life; and Mr. Thornton thought that his job, for the six weeks during which sex ed was supposed to be taught in his class, began and ended at passing out xeroxed pamphlets on family planning, popping a VHS into the VCR and then taking a fifty-minute nap behind his desk.
Whatever the reason, there are few fantasies that can get Chuck off as quickly or as explosively as the ones he has involving Ellie. Obviously, he isn't very proud of this fact, so he tries not to indulge himself too often. But when he's feeling particularly lonely, or just really tired and horny and he needs to get it out of his system, Chuck will call to mind an old favorite.
Sometimes it's the one where Chuck's done something bad or just thoughtless and Ellie "punishes" him for it. (Chuck used that one a lot when he was young and sometimes felt like a burden to Ellie, who was stuck playing mother and father and irritated older sister for him all at once.) (It never helped, by the way. Chuck would always finish feeling guiltier than he had before - not only for being such a responsibility to Ellie but also for somehow getting off on it.)
Sometimes it's the one where Chuck talks Ellie into it. He imagines that he cooks dinner for them (which of course doesn't suck; Ellie taught him how to handle himself in a kitchen) and gives her a neck rub while they sit on the couch, and then leans over her shoulder and kisses her, right on the lips.
Ellie objects quickly (but not immediately, which is key; she lets the kiss go on long enough that Chuck can tell that she likes it) because she has to be sure that Chuck knows what he's doing. She loves him and she's a good sister, and he has to convince her that nothing she could ever do or not do with him would make her less than the best person that he's ever known.
Sometimes Chuck imagines that Ellie is pleasantly surprised in the bedroom. She comments on his size and skill and asks questions, just like she would in real life, that would probably freak any other guy out if she was his sister. (She's had to ask those questions throughout Chuck's life. If she didn't say things like, "Chuck, did you remember a condom?" who would?) Other times, though, dream!Ellie is instructive. Like his very own sex tutor, especially whenever Chuck is in a sexual relationship with someone.
And that's where Chuck's threesome fantasies come into play.
The second most exciting fantasies that Chuck ever has involve his sharing Ellie with one of his girlfriends. Or, sometimes, someone Chuck couldn't possibly hope to date.
Chuck fantasized about having Ellie teach his first sex partner how to give a guy a blowjob, by using Chuck as a practice dummy. He imagined Ellie giving him a practical demonstration of how to eat Jill out. Before Ellie met Devon, Chuck used to picture her having sex with Bryce - just the two of them - because he thought that maybe it would be less gay to picture his male roommate coming if he didn't picture himself as the one making it happen. But after meeting Devon - a now regular guest star in his Ellie fantasies - Chuck gave up the ghost and let dream!Ellie direct him and dream!Bryce towards one of the more impressive solo orgasms of Chuck's life.
It stands to reason then that Chuck would fantasize about Ellie and Sarah, even though he and Sarah have the most satisfying relationship that Chuck's had with anyone.
"But Chuck loves the way I kiss him there," Chuck imagines Sarah saying, looking over at him with what he calls her 'Sexy Spy Glower'. "Right, Chuck?" She is no less intimidating, naked and kneeling at the foot of Chuck's bed, than ever.
Ellie doesn't look intimidated, though, stretched out beside Chuck with her head propped up by one hand, the other hand absent-mindedly stroking Chuck's chest.
"I'm not saying that he doesn't love it, sweetie," Ellie replies. "Just that he'd equally love it if you used a little more teeth. Chuck trusts you not to hurt him even though he's really incredibly sensitive right before he comes."
"Are you that close, Chuck?" Sarah asks, from between Chuck's spread legs.
"I'm-" Chuck would attempt to explain if this were really happening, his voice as shaky as the panting breaths he takes in the dark.
But his own hand is Ellie's in his mind, and she squeezes, cutting off his voice. Chuck wonders what it says about him that he can't get in a word edgewise with these two whenever they're in his fantasies together.
"He's getting there," Ellie answers for Chuck. "So if you're going to try it, try it now. Chuck, give Sarah a little more room, okay, honey?" And Chuck spreads his legs a little more, although there isn't actually anyone gently lifting his balls and pressing an exploratory kiss to the sensitized skin behind them.
"Oh god..." Chuck can't help but say aloud. And he lifts his hips into the grip steadily working his leaking dick, but he doesn't speed up his hand. Because Ellie wouldn't. Dream!Ellie would want to make Chuck wait. She has a point to make and Chuck can just wait until she's made it to have his orgasm.
Chuck imagines the first light scrape of Sarah's teeth against his flesh and it becomes very hard to honor dream!Ellie's wishes.
"Is that better, baby?" Sarah lifts her head to ask.
"Yes... oh, yes..." Chuck says into the darkness.
Ellie smiles. "Good. Now, if you want to make him really go nuts..."
"Ellie... Ellie don't-" Chuck would caution his sister if she and Sarah were really in his bed. Instead he just lies there, entire body singing, waiting, as he pictures Ellie rising and moving around to the end of the bed behind Sarah.
"It's okay, Chuck," he imagines Ellie reassuring him. "It's okay to ask for this here. This is your fantasy! You can have anything you want."
Chuck's hand becomes his own, in mind and body, and speeds up as Ellie guides Sarah's touch down the inside of his thigh. Together they fondle Chuck's balls as he draws up his knees. Chuck reaches down but it's Sarah's fingers that Ellie directs to the opening Chuck can never bring himself to admit to having explored once or twice during masturbation.
"Be really gentle... Yes. You like that, Chuck? Okay, Sarah, he can take a little more... That's right. Oh, Sarah, you're doing so well..." Chuck imagines Ellie keeping up a running commentary as Sarah tentatively strives to please him. He can almost see Sarah's gorgeous eyes looking up at him, from beneath lowered lashes, from time to time as Sarah gauges his reactions.
When he can't wait much longer, Chuck sees Ellie brush back Sarah's hair and press a kiss to the side of Sarah's neck.
"Okay, now, sweetie. Finish him off now," Ellie says. With one hand she cups one of Sarah's breasts, and with the other she guides Sarah's head down towards Chuck's straining dick.
"Oh... oh, yes. Sarah... Ellie... Sarah..." Chuck can't even keep straight whose name he is crying out as he nears climax, and whose he cries out strictly inside his head, but he knows that he is seeing both his wife's face and his sister's as a wave of pleasure hits him that would rock the bed if it weren't contained by his body. He shoots streams of come into his fist and onto his stomach as he imagines Sarah drinking him down, Ellie saying - in her 'Now you listen here, mister' voice - to Sarah: "Uh-uh. You don't pull back until he's all done. That's right... Just swallow, Sarah. Good girl..." And Chuck whimpers as the thought makes his spent dick almost jerk to attention all over again.
In the morning, Morgan will wake him up with the sound of a camera phone clicking. He'll talk about 'sexting' and keeping the passion alive and say things like, "Sure, Sarah's coping. She's got spy stuff to get her adrenaline pumping til she can come home to you, but how are you doing it, man? Going to bed night after night alone?"
And Chuck will just blush and say that he's fine waiting for Sarah to come home from her mission.
He's used to finding imaginative ways to pass their time apart.