Title: Un-fucking-believable

Summary: Tony decides that the best way to help Bruce's control over the Other Guy would be to cross the line as many times as he can, in as many directions as he can. Steve does not approve, but then again, neither does anyone else.

.

Tony started small, which should have been the first warning that he was up to no good. Steve knows that the man likes to push, and sure, some situations call for it, but the way in which Tony goes about testing boundaries is akin to diving off a plane to test air resistance.

It's extravagant and dangerous and only by some miracle does it turn out okay in the end. Usually by Tony building himself a pair of wings on the way down or revealing a parachute that he was attached to the whole time.

No, wait. Tony would just summon his suit and call it training, Cap, it's just like your morning runs except I don't get sweaty and you couldn't hope to match my speed.

…Yeah, it started slow.

Doesn't make it any less dangerous, though.

Day 1 - 3:26pm

Steve watches in bemused horror as Tony shuffles across the shaggy carpet for the fourth lap around the living room, socks scuffing nicely. The super soldier wonders if he should stop Tony before the man hurts himself but it doesn't look hazardous apart from the trip factor.

Then again, it is Tony.

"Do you want to sit down?" Steve asks, twisting his neck awkwardly as Tony passes behind him.

"If I wanted to sit, Cap, I would sit." Tony waves him off but trips and staggers, flailing to keep his balance. He straightens quickly and glances around as if there was even the slightest possibility that everyone wasn't staring at him.

Clint just tries to subtly give Steve and Bruce wide-eyed looks. By the way the archer wiggles his eyebrows, Steve is supposed to tackle Tony, Bruce will open the balcony doors and Clint will throw the billionaire off his own tower.

"What are you staring at, cat piss?" Tony smirks as he starts up with the shuffling again.

Is Steve seeing things or is Tony's hair starting to stand up?

"It's Katniss, you Robo-cop rip-off. If you're going to reference, do it right or go home," Clint fires back with a grin.

"This is my home, you freeloader," Tony retorts. "The giant A on the side of it is just a pity present."

Clint slowly turns to look at Tony, eyes exaggeratedly wide and voice in an understanding tone as if some great epiphany struck him. "You think your funny, don't you?"

"What I think is universally acknowledged as at least a decade ahead of any possible contender, and is studied as the gospel truth in my fields of work." Tony shoots a smirk at Clint. "Just let that sink in for a bit, archer."

Clint screws up his face before it blanks completely. "Don't taunt the secret agent, Stark."

"Hey, calm down. He didn't mean it like that." Steve isn't even sure who he's talking to at this point, the words just come automatically whenever Tony annoys someone.

"Embarrassment, denial, anger," Tony mutters, glancing sideways at Clint when he passes behind Bruce. "You know, Steve, I would believe you a lot more if he didn't look like I caught him trying to suck his own dick."

Bruce chokes.

"That entire sentence makes me want to slap somebody," Clint's admits, looking considering as he tracks Tony's shuffling form around the room.

"Clint-"

"It's fine." Tony holds up a hand and cuts off Steve. "I know when I'm unwanted. I was just leaving anyway."

Bruce glances over when the noise of socks on carpet speeds up, and get treated to the terrifying sight of a Tony shuffling full speed towards him like an out of control stream train.

"What are-" is as far as Bruce gets before Tony reaches out and pokes him. "Hurk-!"

Bruce feels his body jerk in reaction to the electricity singing though him. By the time he recovers, Tony has already sprinted out of the room, cackling with maniacal laughter.

"So that's why he put in the carpet," Clint murmurs.

"Don't," Steve says, not even bothering to look to know that Clint has kicked off his shoes and started shuffling his feet. "Sorry, Bruce. I should have been more comprehensive when I banned his taser-pen."

"It's fine, Steve," Bruce huffs in laughter. "I'm more shocked that he was able to focus long enough to gather that much electricity."

That should have been the second warning.

Day 12 - 8:41pm

Bruce gestures sharply. "The isolation itself would be difficult." He catches himself and crosses his arms but continues with his rapid speech, unwilling to be cut off yet again by Tony. "That particular strain isn't a catalyst, it binds itself to the target and becomes engulfed when –"

Tony scoffs. "Not with the added protein-"

"Thank you, Tony!" Bruce barks out when he's interrupted.

He's vaguely aware that the pause lasts for a brief second but the silence seems like a physical weight. The struggle to keep the Other Guy suppressed is vicious and tiring, only adding to his headache.

"You're welcome, Bruce." The words are perfectly polite, but quiet as they slide off Tony's tongue, carrying a mocking edge as if the man is barely holding himself back from laughter.

Tony swaggers around the bench, tapping half-heartedly at the holograms before leaning a hip against the bench near Bruce. He watches the man clean his glasses roughly, catching a glimpse of green around the temples, and lets out a sigh.

"Look, the fact is; I'm right," Tony calmly dismisses, an hour of arguing filled with solid scientific theory out the window, because that's how logic works.

"Tony-" is as far as Bruce gets before the sheer frustration blocks his throat. He wipes sweaty palms on his pants and takes a deep breath, focusing on anything but Tony's ridiculous hypothesis.

He has no idea why he even bothers. Trying to argue with Tony Stark is like trying to topple a century old oak by slapping it and wishing really hard. He just can't stop, though – the evidence Tony showed is just plausible enough to be an option but the overall thesis is outrageous to the point of stupidity.

"That's a very shallow excuse," is what Bruce settles on.

"I'm a shallow man," comes the retort.

Jarvis beeps quietly, trying to play mediator as the holograms display further excerpts of science journals.

"You think I care?" Bruce snaps out.

"You think I want you to?" The grin on Tony's lips is too sharp, echoed by Bruce's own grip on the bench that craters the metal before he gets a hold of his strength.

Bruce is the first to look away.

Tony picks up a tablet idly and starts playing with it when it turns on automatically. He can only last so long, though.

"Whatever. I'm not one for the squishy sciences, and even I know you're wrong." Tony smirks at the newest high score in Angry Birds and glances up at Bruce through his eyelashes. "There's no need to argue for the sake for arguing-"

Bruce's head snaps to Tony as he snarls, smacking the man's tablet out of his hands. It clatters to the ground and Tony jerks back in shock, hearing a ripping sound a split second later as Bruce's shirt falls to the floor in tatters. Bruce staggers back, suddenly gasping heavily and very, very green.

…

"Code green."

Steve's head snaps up at the perfectly calm tone of the AI, dropping his sketchpad onto the table and lurching to his feet as Thor skids around the corner with a manic grin on his face, already swinging his hammer.

Where did Steve put that shield, again?

…

Hulk whips his head around, searching for enemies but calms quickly when he finds himself in the workshop with an outraged Tony staring at him.

Hulk huffs when it's clear that Bruce is still angry and sits heavily, shaking the tools that weren't held down and making Tony wobble, when it becomes evident he won't be turning back with the scientist still pacing in the back of his mind.

"Hey, not okay! You can't just run when you know I'm right, Bruce!" Tony snatches up the tablet, the only thing making sure it wasn't broken is the fact that it was Bruce's reinforce tablet.

Completely forgetting that he had been playing a game instead of looking at evidence to support his theory, Tony waves the tablet in Hulk's face, having to get on his toes and stretch up to reach eye height with Bruce's alter-ego. "Look at this, Hulk, look at my genius that Bruce insists is wrong."

Hulk turns away from the flailing, gaze bored as he examines the lab. Bruce cheers him on. Humans are weird.

"Are you seriously ignoring me right now?" Tony makes a frustrated sound, throwing the tablet onto the bench and climbing onto Hulk's leg, having to brace himself on a green shoulder to not fall off the uneven terrain. Tony glares up into bored, glazed over eyes. It was high school all over again. "Just because you're bigger than me-"

Hulk simply huffs in amusement, the gust of air blowing back Tony's hair and making the man squint, startled out of his rant.

Unfortunately for Tony, Hulk then decides to have a nap and flops down. Having lost the stability of Hulk's shoulder that he was leaning against, and competing with the shifting thigh underneath him, Tony falls with a short, startled cry.

The breath is knocked out of him and Tony gets intimate experience as to how uncomfortable muscles are to lie on. He groans and hauls himself up to a kneeling position, stilling at an honest to God snore from Hulk.

"Did you just fall asleep?" he asks in shock. "Are you shitting me, Hulk?"

The glass doors swoosh open, Thor and Steve barrelling through, and the God has to catch himself on the edge of a bench to slow himself down.

"Tony!" Steve cries, skidding to a stop and gaping at the scene.

Tony gestures sharply at the Hulk who he's still kneeling on. "Who even falls asleep that fast?"

Thor points at himself and opens his mouth to speak.

"Don't even talk, Thor," Tony interrupts in frustration.

Day 20 - 9:29am

The car swerves in the recording, identified immediately as Tony's because of how expensive it looks. The car jerks to the side, missing oncoming traffic by a hair's width, and comes under control surprising quickly considering the speed it's going.

The sleek curves of the chrome coloured car bulge and strain as the vehicle pulls over to the break down lane, smoothly coming to a stop despite the rocking and windows shattering. The roof bends outwards and rips off, the convertible factor helping.

Hulk leaps out, huffing and snarling as he looks around. Eventually he glances down at an annoyed looking Tony who gestures at the passenger seat and speaks rapidly, the camera not detailed enough when zoomed in that far to pick up his lips moving, but the way Tony moves his hands make it obvious.

Hulk seems to roll his eyes at whatever Tony is saying and stomps over, gingerly pulling out the passenger seat to leave it on the ground so he could get into the car, flopping over the back seats with one leg stuffed into the space where the passenger seat used to be, the other hanging out of the car.

Tony drives off, out of camera range.

The recording pauses and Steve turns very slowly to the grimacing Bruce and highly amused Tony, both of the scientists on the couch beside the super soldier.

"In the middle of the highway?" Steve sighs. "Really, guys?"

"I never noticed the guy in the blue Toyota was texting. That was very dangerous of him." Tony shakes his head in disappointment.

"Excuse me?" Bruce turns to the genius.

"I should have side-swiped that asshole," Tony adds on.

"You are absolutely incredible," Steve says in a monotone voice. "Not in the fun way, either."

"Well, really, it was Bruce's fault," Tony defends, turning to his fellow scientist. "It's been nice knowing you, but from the fact that Steve even has the recording, Fast and the Furious will most likely run you over with his ship soon."

"Stark!" Fury barks out, appearing in a window over the footage, taking up the entire TV screen.

"God, I missed your heavenly voice," Tony greets the director. "But you really need to speak up, you're so quiet."

"You are the stupidest mother fucker-" Fury visibly reigns himself in, disappearing off screen for a brief moment and coming back with a controlled expression. "You know what I'm going to do, Stark? I'm going to get your file and write 'lower your expectations' on it. Right across the front. In red pen."

"I think someone's jealous."

"Jesus, Stark, shut up," Natasha interrupts in the background of the camera.

"There's an emotion there," Fury admits. "But it's not jealously."

"Is it lust?" is as far as Tony gets before Steve covers his mouth with a hand.

"I am so very sorry," Steve says to Fury before turning to Tony. "Bad Tony. Don't make me get Pepper."

Muffled protests meet his threat but Steve just places another hand at the back of Tony's neck and the man is effectively trapped in the super soldier's grip from the ridiculously unfair strength that the blond holds.

"I'm sorry, Fury," Bruce speaks up, ignoring the flailing Tony who isn't even trying that hard to get away from Steve. "I thought I had better control over the Other Guy but I've… shifted twice now and even though I don't hurt anyone I'm beginning to think that I should leave-"

"Your punishment," Fury begins, cutting over Bruce. "Is that you are on Stark duty. Indefinitely."

Everyone does their best to ignore Natasha breaking down in uncontrollable laughter.

"I- I've shifted in heavily populated areas-" Bruce tries to reason.

"And Stark is still more of a threat than you," Fury dismisses.

"To be fair, Tony is more of a threat than you," Bruce fires back.

Fury pauses, staring down Bruce. "The Hulk has done nothing but pout. Give it an enemy, it becomes a savage monster. Give it a friend, and it has no idea what to do with itself." Fury leans back into his chair. "Make no mistake, you are a threat and we will still be keeping a close eye on you, but you've made progress in training it. Keep it up."

"With all due respect, you don't train the Other Guy-" Bruce stutters to a halt when the window closes, signifying Fury hanging up. He sighs, dragging a hand across his face.

Steve doesn't say anything, watching Tony closely ever since he felt the smile pressing against his palm.

Day 34 - 12:16pm

Tony and Bruce are arguing, standing close enough that if one of them swung at the other Steve won't make it, which of course is making the blonde twitchy. He can only hope that Thor would step in, but the God is distracted with breaking the sandwich maker.

There is no hope for the two spies, either. Clint is perched on the fridge and wiggling his eyebrows at Natasha, forming a plan of attack that she is very pointedly ignoring as she eats her lunch at the table.

Steve considers the situation again. The two scientists are standing in front of the kitchen bench, so Steve doesn't have an obstacle in his way. It would still be better if the two moved further away from the kitchen with Clint and Thor, and came closer to the table where Steve and Natasha are sitting.

Steve wishes he could at least see Bruce's face to tell if he's close to 'Hulking out' but throughout the argument Tony has been pacing up and down across the room and settled facing the rest of the Avengers so Bruce's back is to them.

Unfortunately, Steve doesn't have telekinesis. (Although apparently that's a thing these days with mutants.) He also has no idea about what the two are arguing over. Tony and Bruce are supposedly using English but Steve swears that for a period of about five minutes they slipped into Latin.

"I have hard evidence," Tony contests. "The experiments were done and the results were observed, plain and simple. How hard is it to understand that your method is old school – and how long will it take to sink in? I have a meeting to get to."

Bruce cries out in wordless frustration, running his hand through his hair. "Your theory is so wrong it physically hurts to listen." He gestures vaguely at the tablets on the kitchen bench, abandoned next to sandwiches when they started the argument, forcing Tony to step back to avoid being hit. "I've seen the bogus 'research' you've given me as evidence. It might not be your field but you've done enough investigation that you should know better."

Bruce is walking forward now, making Tony back up. Steve tenses, ready to act.

"The data is unreliable and invalid; all of the methods were done by seven year olds who were told to write a story, because it certainly reads like it, and they don't even have controls - don't even get me started on the bias. You're a genius, Tony, think." Bruce is gasping slightly from saying everything without taking a breath.

Tony, from where he has been backed into the kitchen bench, has his arms crossed. Bruce only just seems to realise what he's been doing and goes to step away, but blinks at how relaxed Tony looks, the man leaning back on the bench with a small smirk.

"Your eyes have been green for ten minutes now," Tony informs him, practically dripping smugness.

Bruce stills, right along with everyone else.

"You're right, Brucie, I am a genius." Tony passes by with a strut, off to a meeting he's already half an hour late to.

Bruce blinks, feeling the steady presence in the back of his head, and registers that the Other Guy hasn't tried once to break out despite the anger that definitely should have broken the levee. He then thinks of all the other situations in which Tony had pushed for Bruce to shift.

The four weeks of arguing was just a ploy for conditioning - desensitising.

"I've already told Fury; you can't train the Other Guy," Bruce contests to Tony's back.

"Of course not," Tony responds. "I was training you."

Bruce chokes out a laugh, only just registering that this was an answer. "I love you."

"Love you more, Brucie bae," Tony calls over his shoulder as he disappears into the lift.

"Let's not make this a competition," Clint speaks up. "I get really competitive."

Natasha perseveres with her lunch, intent on ignoring the situation, while Thor tries to look casual holding two separate sides of the sandwich maker that should definitely not be separate.

"Un-fucking-believable, all of you," Steve sighs into his hands.

"Language."