"You absolutely promise this won't be permanent?"

"I swear it. Forty eight hours, max. It'll wear off gradually over the last couple of hours but until then, you'll be sixteen again."

"Greattttt. Because that's every grown man's greatest fantasy, to be pimply with a squeaky voice right before he's even had his growth spurt all over again."

Clint was understandably a little unhappy about the whole situation. He'd drawn the short straw, though, and now he had no choice but to follow through, no matter how hard he might try to talk his way out of it.

"How do you even know this will work in the first place? I'm guessing you didn't exactly use yourself as a guinea pig, Banner."

Looking up briefly from the monitor he was observing as he calculated the dosage based on Clint's weight and height and current age, Bruce nudged his glasses up a little higher on his nose, delaying the need to answer. "Well...I mean...the mice responded well."

Clint damn near shrieked at him. "Mice?! You mean you've only tested it on rodents?!"

"Well," Bruce muttered, "Every scientific theory has to start somewhere."

"And now you're back to calling it a theory!" Clint's eyes bugged out of his skull, backing away from the workbench hastily. "You're joking, right? About this whole stupid idea?"

When Bruce shook his head, eyes full of sympathy, Clint slumped dejectedly, reluctantly resigning himself to his fate. Whatever it might be.

"Fine," he grumbled, "Just make it quick so I can get this mission over with and go back to being a full grown man with all his short and curlies again."

Scrunching his face up as he pinched the bridge of his nose, Bruce just nodded, doing his best to bleach that image from his brain as he instructed Clint to sit down and lay back in the chair. "You'll likely experience a little disorientation, your balance will be a little compromised to begin with until you adjust, but your mind will be your own. You'll have all your memories, all your personality and...quirks...will be intact."

"Oh, I suppose you and Pym just asked your little mice subjects to clarify all that for you in a handy little questionnaire, huh?"

Ignoring Clint's little outburst, Bruce drew back on the syringe as it filled with the serum that would revert him back to his teenage body. "Okay? Ready?"

"Do I look ready?" Clint muttered, his eyes wide with trepidation and displeasure.

Bruce shrugged. "Not really."

Over the course of the forty seven minutes following the injection which flooded Clint's veins with the highly experimental solution, the Avenger's body shrank, in both height and muscle mass. The battle-weary creases at the corners of his eyes smoothed until they were no longer a visible reminder of the seven layers of hell he'd survived. The scruff on his jaw and chin retreated, leaving only the faintest hint of fluff on his top lip, while his voice lost its tenor. Almost disconcertingly, however, his nose still heralded the crooked memories of every time it had been broken in a fight, and the reminders of innumerable gunshots, stab wounds and other miscellaneous injuries still scarred his skin.

"Aw futz," Clint croaked as he tested out his resurrected, under-developed vocal cords. Looking at himself in the mirror, he cringed, resisting the urge to reach up to squeeze the zit that itched next to his left nostril. "Forty eight hours, right?"

For a moment, Bruce didn't respond. He was gawking awestruck, foremost at the serum's success, but also at the sight of sixteen year old Clint in all his gangly glory; he hadn't grown into his limbs, yet, and the years of hard work put into his physique hadn't yet passed. He hadn't expected the scars to remain, either; he had, foolishly he now realised, assumed that the formula would have somewhat regenerative properties.

"Banner! Don't stand there staring at me like I'm your Frankenstein's monster success story; answer me! Forty eight hours and I can go back to normal, right?"

"Right!" Bruce snapped out of his reverie, nodding emphatically at the teenaged Hawkeye. "So, better make them count. Unless you want to have to go through this whole thing again."

Eyes wide, Clint squawked a curse. "Not a futzin' chance."

It started slowly at first, so gradually it was imperceptible to the naked eye. The crackling pop of his maturing voice started to shift up an octave instead of dropping one. The shoes that had fit perfectly that morning started to slip off his feet with every step. The fuzz on his lip receded one hair at a time without him so much as lifting a razor. It wasn't until his gums painfully swallowed his wisdom teeth forty two hours in that Clint realised something was horribly wrong.

"Fix this!" Clint shrilled at Bruce as he stormed into the lab with all the fury his now twelve year old self could exude. "I'm supposed to be getting older, not younger!"

Bruce's eyes expanded in perfect synchronicity with his jaw dropping.

"I...none of the test subjects experienced anything like this. I'm not even sure what...I mean...I can't fix what I don't understand, Clint."

"Then understand it! Figure out what's happening and fix it!" the younger version of Clint Barton snapped, his voice no longer squeaking with the effort of pushing words past vocal cords that were still figuring out their role in this world. "An hour ago my balls were still right where I'd left them and now they're back up somewhere between my bladder and my spleen along with the pitch of my voice! Fix it so they drop back down where they belong or so help me God, Banner..."

Squashing down the absurd instinct to deliver an unnecessary anatomy lesson, Bruce exhaled slowly. Bracing himself for another outburst, he held his hands up, palms out so as to placate the already irate archer. "Give me time. I just...I need some time to run tests and figure this out, but I promise, I can fix this." He paused. "I think."

"It's the 'I think' part that worries me," Clint groaned. He was almost certain that in the five minutes since he'd walked into the lab, he'd shrunk another inch, and the pre-pubescent blemishes had faded from his now perfectly smooth skin. "I swear I'm losing two years every couple of minutes now. If you don't fix this before I'm back in diapers, I will sink my milk teeth into you!"

"Six hours," Bruce pleaded, "And that's if I take a lot of shortcuts. But I'm going to need at least six hours to run tests. I'll need blood, hair and a cheek swab. To begin with, at least."

Gritting his teeth, Clint scrunched his now nine year old face up in contempt. "I'd even jerk off into a cup if it would help but I'm not sure I'm even capable of that any more."

Pinching the bridge of his nose, Bruce rubbed his eyes with the pads of his thumb and forefinger, his glasses resting on his knuckles as he sighed. Admitting he needed at least six hours to even run the tests was one thing, but trying to tell Clint that he would need adult supervision for the duration of those six hours was going to be another thing entirely.

"Gimme the goddamn drink! I'm teething and have nappy rash that itches worse than a case of the clap because someone -" the piercing pair of literal baby blues shot daggers in Bucky's direction, "- forgot to powder my ass!"

At two years old, it was disconcerting hearing that sort of language spouting from Clint's tiny, but not yet completely toothless mouth. The team that wasn't hunting for answers in the lab was officially stuck on babysitting duties. While Clint retained his memories and his ability to speak, his fine motor skills were on the decline, resulting in the need for a little more help getting around. Pym had suggested it was possibly only a matter of time until even his vocal cords reverted back to being unable to form sophisticated sounds, too. Clint hadn't liked that, and was in the middle of a particularly foul mouthed tantrum as though to make the most of what time he had left to do so.

"Well next time tell one of us you need to crap yourself and we'll take you to the bathroom so you can do it in the big boy's potty instead," Bucky smirked, clearly still not over the trauma of changing his teammate's dirty diaper, and still cursing Tony for suggesting that they draw straws for it, too; especially when he was positive Tony had somehow cheated. Just because he looked like a toddler didn't mean it was any less Clint. "Besides, you can't metabolize alcohol any more. So, suck it up. Have a binky instead."

The look of pure rage blazing in Clint's eyes when Bucky tossed a pacifier in his direction was enough to force Steve's hand, as he stepped in and lifted Clint into his arms. "Okay, that's enough out of you. I think you need a nap."

"No I do not need a nap!" Clint protested, but even as he did so, he yawned, snuggling into the crook of Steve's neck and shoulder. "I am a grown ass man. Grown men don't use binkies or take naps or...or..."

"Shit in diapers?" Bucky teased, eliciting a tempestuous shriek of indignant wrath from the two foot tall, blond haired boy with eyes bluer and colder than icicles as he tried to fling himself from Steve's arms in an effort to sink his sharp little fingernails into Bucky's face.

"Okay," Steve laughed, drawing the word out slowly as he wrangled Clint in his arms, "Enough. Just because you look like a baby doesn't mean you need to act like one."

Watching with an eyebrow raised in bemusement, Nat piped with an affectionate taunt in her voice, "This is Clint we're talking about. Acting like a baby is sort of what he does best." Clint shot a furious look in her direction, but with his plump infantile features, the scrunched up button nose and pouty lips only served to remind Nat of a Cabbage Patch doll, making her own face contort with the effort of holding back her laughter. Sucking in a breath to try and calm herself, Nat looked at Clint sympathetically, walking over to take him from Steve's arms and cradled him close to her chest to try and comfort him. "Just hang in there a little longer. Banner, Pym and Stark are all working on a way to reverse this, but you gotta be patient. They can either do it fast, or they can do it right. Which would you prefer?"

"Both," Clint muttered. "Can't we just get Strange to do his magic wizard thing and take me back to before I agreed to this nonsense? So I can use my brain for once and refuse to do it at all?"

Glances were exchanged between the group; the idea had been floated briefly, but was quickly rejected. The mission itself had been a triumph, and a diplomat's sixteen year old son had been saved from a politically fuelled abduction attempt. Any effort to distort the prose of history could undo all that hard work, and none of them were willing to take that risk.

"You know why we can't do that," Steve sighed softly, "Just...be patient, like Nat said."

Tears welled in Clint's eyes, and for a moment, it was easy to forget that there was a man in his mid-thirties trapped inside that baby's body. His bottom lip trembled, and his eyes screwed shut, sniffing loudly as he tried to force the sob of despair back down his throat before it could escape. Fat, lazy tears of pure frustration slipped down his cheeks as he looked around the room at each of his teammates, silently pleading with them to help him. He knew they were doing all they could, but he was losing hope. When he opened his mouth to speak again, all that came out were a few babbled, incoherent syllables.

"Oh no..." Nat's hand flew to her mouth as it dropped open in horror. None of them knew what would happen if Clint continued to shed months of his life in mere minutes, and it was clear now that he didn't have many months left to lose. "We're going to get you back to normal, Clint. Until we do, we're going to look after you. You're going to be okay."

Moments after the now four month old baby Barton fell asleep in Natasha's arms, Bruce summoned Steve to the lab. The sombre look on his face wasn't promising.

"He's stopped growing younger," Banner frowned, cleaning his glasses on the hem of his shirt, "But...we still can't figure out how to reverse it. Barton's antibodies should have kicked in and essentially started eating at the serum as it attached itself to his cells, but, the serum was too strong. We could try giving his immune system a boost, but if his white blood cell count raises too high, then...that in itself won't be good, either."

Looking Steve in the eye, Tony folded his arms across his chest, and shrugged. "The alternatives are to either let him grow up all over again," he quirked an eyebrow at the look of disbelief on Captain Roger's face and held his hands up, demanding patience before he continued, "Or we keep looking. The solution is here," he tapped his temple and shrugged again, "We just need to dig around in the grey matter to find it. Until then, I guess we all just signed up for Parenting 101."