## Probability

### Work Text:

Darcy waltzed into the lab where Tony and Jane were bending over a machine, overseen by the recently-arrived Sif.

“Are you sure this won’t blow up my Tower?” Tony asked as Jane adjusted something.

“Fairly certain,” Jane replied.

Darcy distributed coffee, pausing before she allowed the Asgardian to have any. Sif shot her a questioning look, and she said, “I dunno. The last time we gave one of you people this stuff, an innocent mug lost its life.”

“Just give her the coffee, Darcy,” Jane instructed.

“Hey, shouldn’t it be ‘righty tighty?’” Tony put in over her shoulder.

“Stop distracting me, Stark.”

“Okay, if you could avoid smashing this mug, I’d be thankful,” Darcy said, holding it out.

“I will do my best, Lady Lewis,” Sif told her, reaching for the cup.

Their hands touched, the machine sparked, and the doomed mug tumbled to the floor, splintering into pieces and washing coffee over the feet of the women standing over it.

“Aw, come on, she even warned you!” Tony complained. “That was my favorite coffee cup!”

“No it wasn’t,” Jane told him.

“Uh, Jane?”

“Hang on, Sif.”

Tony frowned. “Wait, she called you ‘Jane.’ Doesn’t Sif usually—?”

Jane looked at Darcy, then at Sif. “Hang on. Say that again?”

“The only thing I want to come out of your mouth is ‘I can fix this,’” said Sif’s voice. “No technobabble, just, ‘I am so, so sorry, Darcy, and I can fix this.’” Jane stared at her. “That’s your cue,” she prompted.

“Oh…” Jane replied, realization dawning.

“Lady Foster, we appear to have—” Darcy’s voice began.

“Oh! You body swapped them!” Tony pointed out.

“Yeah, thanks for that,” came the annoyed tone from Sif’s mouth.

“What did you do, reverse the polarity?” Tony wondered.

“I do not believe I am adequately prepared to do battle in this form.” Darcy’s voice sounded more serious than it ever had in her life (except maybe the week before when she’d caught Tony trying to make off with the last box of Pop Tarts).

“You can do battle with a tiny scientist when she needs to get to bed after a science binge, and that’s good enough for me,” Sif!Darcy shot back.

“Just wait a second, I can totally make this right,” Jane vowed, and dived into her machine.

“Yes! Words I want to hear!” The phrase sounded strange coming from Sif, and Tony looked at her sideways.

“Hey, you know…” he began, and both Sif and Darcy focused on him, awaiting the inevitable. He swallowed nervously beneath the imposing scrutiny, but continued. “You ever wish you could... make out with yourself?”

“My Lord Stark,” said Darcy!Sif. “Now is hardly the time for lecherous actions.”

Sif!Darcy, on the other hand, said, “Totally.”

“What?” said Darcy!Sif.

“He’s right. I totally have. We should make out. It’s gonna take a while for Jane to fix us anyway, right Jane?”

“Uh…” Jane replied, poking her head out from beneath the machine. “Yes? I’m pretty sure you’ll need to be touching for it to work, but it doesn’t have to be that much.”

“Great; let’s do this.” Sif!Darcy moved toward her own body, while Darcy!Sif looked apprehensive, especially at the sight of Tony’s face, which was effectively communicating his glee at his front row seat (which was only slightly diminished by the lack of popcorn).

Darcy!Sif held out a hand. “What makes you think I am interested?” she asked icily, in exactly the same tone Actual!Darcy used when the guy from the PR department had asked her out three weeks ago.

“Uh, because if we don’t, we’re going to wonder what it would have been like for the rest of our lives?” Sif!Darcy cajoled. Tony nodded emphatically.

“Almost there…” Jane ground out from within her machine.

“I do not wish to,” Darcy!Sif said, crossing her arms.

““Why not?”” Sif!Darcy and Tony whined in unison. “Shut up, Tony,” Sif!Darcy said, shooting him a deadly look. Then she stepped closer to… herself, and repeated, “Why not?”

Darcy!Sif blushed. It wasn’t a strange look on Darcy, but the knowledge that it was Sif doing the blushing...

“Because,” the warrior explained, wrapping each of her hands around the opposite elbow, “If I am to kiss you, I would rather enjoy the experience from inside my own skin.”

“Oh,” Sif!Darcy breathed. “Yeah, I… guess I understand that.” She reached out and brushed her fingers over the other woman’s hand.

Both gasped.

“What?! What happened?” Jane said, leaning away from the sparking machine.

“Am I me?” Darcy’s voice asked Tony.

“I dunno, which one are you?” he answered.

“I’m me!” Darcy insisted.

“But…” Jane scratched her head, puzzled. “I don’t think I actually did anything.”

“What do you mean you didn’t do anything? They swapped bodies!”

Sif rolled her eyes. “Did Prince Thor aid you in preparing the libations?”

Darcy looked confused. “Yeah, I mean, he was in the kitchen with me, but—”

Sif sighed. “That explains why he did not return with you,” she muttered.

“What was that?” Tony said, leaning toward her.

Jane blew out a long breath and stood. “It’s a pretty obvious situation: Sif likes Darcy. She probably told Thor and he probably tried to convince her to go for it but decided to take matters into his own hands when she didn’t.”

“So there was something in the coffee?!” Tony squeaked, peering at the bottom of his empty cup. He put out a tentative finger and poked Jane in the shoulder. “I’m not a woman,” he observed when he reopened his tightly shut eyes.

“No, it was sorcery of his mother’s,” Sif explained. “I delivered a package to him when I arrived, though I did not know what it contained.”

“So, this wasn’t your machine’s fault?” Tony asked.

“No, but it could have done something like this.”

“How?”

Jane shrugged. “Probability.”

“Leave quantum mechanics out of this.”

Sif frowned and crossed her arms. “I will not be so open with His Highness about my feelings next time,” she said.

“Hey, don’t you think you’re getting a little ahead of yourself?” Darcy objected, scooting closer and lifting her face toward Sif’s. “Maybe you should focus on the now before moving on to next time.”

“What do you—” Sif began, totally clueless despite Darcy’s increasing nearness.

“Oh my god, Tony; you’ve got boobs!” Jane shouted, pointing.

“I—what?!” the billionaire squawked, panicking and yanking at the neckline of his shirt. “No, I don’t,” he reported sullenly.

“No, you don’t,” Jane agreed, “But you missed Sif and Darcy’s first kiss, so I win.”

Tony pouted as Darcy turned and put her arm around Sif. “Tell Thor we said thanks,” she said to Jane. Sif blushed, nodded, and pulled Darcy with her out of the lab.

A few seconds after they exited, Jane’s machine sparked again, causing the lights to go out in the lab.

Tony demanded, “What’s this all about?”

“It wasn’t me,” Jane replied immediately.

“Wait…” Tony’s voice said.

The lights flickered back on, and ‘Jane’ regarded her chest. “I’m a woman!”