The thing is, none of them know what's happening at first.

Hulk is roaring loudly, gleefully throwing anything that gets close enough for him to reach. Sam is the only one with eyes on him when he gets hit — something glowing and bright purple — and then Hulk is shrinking.

Sam tips his head to activate his com hands free, and then says, "Uh, we've got a problem. Banner's down and out, and I'm going to have to pull him out before he gets mobbed." And then Sam is tucking his wings, diving after the still shrinking form.

Something's wrong.

Sam can tell something's wrong – Bruce is thinner than he should be, shoulders narrower, but Sam doesn't have time to deal with it before he's scooping Bruce up and weaving through more weird purple bolts, what the fuck is his life. He's not sure what they are, exactly, but if they can take down the Hulk, he doesn't want to find out.

The extraction is going just fine, Sam's out of the thick of it and headed toward the quinjet, when Bruce starts blinking awake and everything goes sideways.

"What the…" Bruce's exhaustion is clear, as it always is when he turns back, but there's an underlying thread of something Sam doesn't recognize in the short statement. Not until Bruce continues.

"What the fuck oh my god are we fucking flying jesus goddamn christ put me down!" Bruce says, somehow all in one sentence.

"I'm not putting you down in the middle of aliens that shoot mystical magical purple weapons, dude," Sam says easily.

"What the– who the fuck are you?" Bruce asks, which is about when Sam realizes that something is very wrong. "Am I– where are my clothes?" Bruce follows, which is when Sam remembers that while a sense of humor is important, sometimes laughing is not polite.

Sam sets Bruce down gently at the end of the quinjet's loading bay and takes a proper look.

It's not like he spends a ton of time around Bruce — Bruce spends most of his time with Tony or in the labs or with Tony in the labs, and Sam spends a lot of time with Bucky, who never wants to be anywhere near Tony or labs, so their paths don't cross often.

But they cross enough that Sam can tell the difference. Bruce's shoulders are slimmer, and he's missing a lot of muscle mass. His wrists are thinner than they should be.

But even more noticeable than the loss of mass, now that Sam's up close, is how young he looks. His eyes are familiar, dark and shadowed, but his face is unlined, and all they grey that was starting to show in his hair is now gone.

If Sam had to guess, he'd say the person in front of him was… maybe 17. Certainly no longer approaching 50.

Bruce shifts, awkwardly, crossing his arms across his chest to cover himself, and Sam is startled from his brief examination.

"Oh, fuck," he says. "Wait, here." He pulls out a blanket from one of the crates nearby and tosses it to Bruce, who gratefully wraps it around his shoulders.

Sam thanks God and Tony Stark's innovation for the stretchy pants that grow with the Hulk that Tony had made. This situation is awkward enough.

"Uh." Sam says. Bruce looks up at him.

Sam stalls. What do you even say to your suddenly teenaged coworker?

Bruce is eyeing him with extreme suspicion, but seems slightly less poised to run than he did before the blanket.

"How old are you?"

It might not be the most urgent question, but Sam really doesn't know where else to start.

"How old are you?"

Sam pulls his goggles off and runs a hand over his head. "Too damn old to be dealing with this shit," he mutters to himself. "Forty," he says louder. "I'm forty."

"Fifteen," Bruce says, and Jesus Christ he's an actual child. He's younger than the spider kid.

"How do your wings get enough aerodynamic lift to counteract the uneven weight distribution on the rostro-caudal axis?"

Right. Clearly still a genius. Sam pulls his wings in completely and turns, letting Bruce get a good look at the jet pack that provides all his thrust, because he figures the basic tenets of dealing with Bruce Banner still apply — distract the man with science, and he'll usually forget to be awkward.

Bruce reaches out, his face awed, but then after half a second he snatches his hand back as though he's been burned.

It's at that moment when Tony's voice comes through his coms. "Wilson? You and Jolly Green good over there?"

Sam activates his com manually, figuring that'll give Bruce a chance to track what he's doing. "We've got an… anomaly, but nobody's in current danger."

"Copy that, Bird Boy. We should be able to mop it up out here."

"I'm not an anomaly," Bruce says, chin jutting out in a stubborn expression.

"Really?" Sam asks. "Then how did you get here?"

Bruce frowns, and his eyes flick up and to the left.

Sam can see the moment when Bruce realizes that he doesn't know the answer, and he watches Bruce's face shut down, close off, and turn away. Just before it does, though, Sam sees the moment of pure panic and fear, and shit.

Bruce takes a step back. Sam knows better than to reach out.

"Hey," he says instead, pitching his voice soft and soothing. "Hey, it's fine, it's cool, we'll figure it out."

Bruce does not look convinced in the slightest — in fact, he looks slightly concerned at the implication that Sam doesn't know how he got here either — which is, of course, when Tony decides to make his appearance.

And Tony doesn't do anything with subtlety. He descends in the suit and lands right next to the young Bruce, flipping up the faceplate and peering at him. "Whoaaaaaaa. Tiny Banner!"

Bruce frowns, his thick eyebrows furrowing. "Who are you? How do you know my name?"

Which is when Steve jogs up, pulling off his helmet, and makes everything even more complicated.

Bruce's eyes go wide, disbelieving.

Steve tips his head, making his familiar concerned puppy face. "Bruce? Are you alright?"

"You're… you're…" Bruce stammers.

Which, yeah, between Tony's suit and Steve's face in every goddamn history book imaginable, those are probably the most likely to freak Bruce out.

"Maybe we deal with this back at the Tower?" Sam suggests.

"I'm not going anywhere with you!" Bruce says, his features cast in a terrified, stubborn rage. "You kidnapped me!"

Tony blinks. "Interesting theory, String Bean, but not quite."

"Right, because I'm going to believe my kidnappers when they tell me they haven't kidnapped me."

The sarcasm rolls off his tongue so naturally, it seems to take Steve a moment to recognize it, but when he does, he pulls himself upright, into full "Captain America talking to the public" stance, and says, "We're not keeping you against your will."

"Wait, what?" Tony cuts in. "Yes, we are! We are definitely keeping him! Or do you want to let a teenaged Bruce Banner roam the countryside with no knowledge about the state of the world, none of his usual protection, and no idea when he might turn back?"

"We can't just kidnap him!" Steve says.

"Sure we can," Tony says. "It'll be temporary. Probably. I think."

"That's not reassuring, Tony," Sam says.

Tony shrugs, his suit folding down around him. "I didn't really intend it to be. Tony Stark," he says, sticking out his hand to Bruce. "Welcome to the year 2019."

Bruce's jaw drops. He looks at Steve, and then Sam, as though one of them will tell him this is all just an elaborate joke. Sam just shrugs a bit.

Bruce blinks, looks around, and then sinks into one of the bay seats and drops his head into his hands. The rest of the team boards and the bay doors close, but most of the fight seems to have gone out of Bruce.

..

"Look I promise I'm not going to kill you," Tony says. "I just… I know you don't know me, but I know you, and I know you'll feel more at home in the lab. Plus, come on, you know you want to see all the future science shit, don't even try to tell me you don't."

Bruce seems to be vacillating rapidly between skeptical and overwhelmed, but in the end he does wind up following Tony to the lab, where Peter is bent over a microscope.

"Hey, webhead," Tony says absently. Peter looks up.

"Dr. B? Whoaaaa, how'd you get so tiny? Are you younger? You look younger. You look younger than me, actually. How'd that happen?"

Bruce blinks at the rapid influx of words. "I… don't know?" he finally says, apparently opting to just answer the last question.

"Was it magic? I bet it was magic. Magic is the worst, man."

"It was probably magic, because sorcerers are dicks," Tony puts in. "Bruce, come see my homemade particle accelerator, you're gonna love it."

"You do not have a particle accelerator in this building."

"I think you'll find that I do."

"I don't believe you."

"Then come see it!"

Tony hasn't gotten to impress Bruce with his lab in actual years, and he can't say he's mad about having the opportunity.

But even as he does, the voice in the back of his head worries. What if this isn't temporary? What if he can't fix this?

What if Bruce is just fifteen years old now? No Hulk, no attachment to the Avengers. Will Bruce walk away?

What would they do if he did?

Tony thinks about the lab without Bruce, about just him and Peter chattering with no quiet, calm presence to steady them, no one to make snarky jokes.

The thought is intolerable. Even if this is permanent, Bruce has to stay.

Tony is deep in thought, but Bruce's quiet voice breaks through. "What happened to Jen?"

Tony blinks.

"Who?"

"Jen. My cousin Jen. If this is the future… did she become a lawyer like she wanted? Is she okay?"

"J?" Tony says. "Is that a good answer?"

"Ms. Walters is practicing family law in New Jersey," JARVIS says.

"Wh- Who is that?"

"That's JARVIS. He's my AI, he pretty much runs the building. But I'm pretty sure he got that from a basic google search."

"A what now?"

"...that's adorable. What year are you from? Nah, doesn't matter. Google - it's a global search engine on the Internet. Don't ask me to explain the Internet, though. No one can explain the Internet, not even a genius."

Bruce blinks at him, and then blinks again, heavier. "But he's right? Jen's okay?"

"JARVIS never lies. Unless I ask him to. Which I haven't. But you should sit. Time traveling or shrinking or whatever the hell happened to you probably gets exhausting."

Bruce blinks again. "I am… bizarrely exhausted, yeah."

Tony guides him to the lab couch — it's seen all three of them sleeping on it at one time or another, and one memorable time all three at the same time, when they tried to science binge too hard.

It takes less than five minutes for Bruce to crash. Tony grins, tucking the couch blanket over him, and gestures to Peter to follow him out. For once, Peter takes the hint to be quiet until they make it out of the lab.

…

The post-mission pile of pizzas has just arrived when Tony gets an alert from JARVIS.

"Sir, it seems Dr. Banner is returning to his normal age."

"Oh, thank fuck. If he wakes up, let him know that there's pizza?"

And, with that, it becomes nothing more than another bizarre day in their lives. Not even the most bizarre. It might just break the top ten though.

..

For: HSWW: C&A: Auction, Hufflepuff prompt 1: deaging, 1982 words; Bex's basement: Nat, trait: suspicious