The day Rockwell finished the antidote (or whatever), Casey brought Donnie a little toy car. It was remote-controlled, and battery-powered, and Donnie's eyes were the brightest thing in the whole universe when their human friend knelt down to show him the controller. It was cute, but mostly it was to keep him busy while Rockwell and April set up the lab—putting the scene of the accident back together, down to the last broken beaker, and getting all the new chemicals ready.

The whole thing kind of reminded Mikey of the Kid Flash origin story, Barry Allen recreating the lab accident that gave him super powers for his girlfriend's nephew, and whoops, who knew lightning would strike the same place twice and give lucky little Wally West a tap into the Speed Force?

April assured him there would be no lightning involved in Donnie's case. Which was good, 'cause comic books made it pretty clear that lightning hurt.

"Mike," Donnie called from the other side of the room, smiling ear to ear. "Mike, come play with me!"

Man, Mikey was gonna miss that. And he was gonna miss the way Donnie put his arms out to be picked up, and the way he'd giggle behind his hand at all of Mikey's jokes, and sit on the counter to help him make lunch, and drink in everything he said like a wide-eyed little sponge.

But Mikey missed his big brother, too. So, since he was gonna miss him either way—

"I'm comin', munchkin," he said with a sideways grin, hopping to his feet. And if the look his father gave him on his way by was a little too knowing, a little too understanding… well, whatever. Sensei always said he had a great imagination; Mikey was really good at pretending.

And he could totally pretend like this wasn't gonna hurt. He could pretend like it was okay when things went back to the way they used to be—when Donnie was more likely to slam a door in his face than ask to read comic books with him, or watch T.V., or make shadow puppets on the rice paper walls of the dojo. It wasn't right that this accident should change anything, or that he should want it to. He loved Donnie no matter how big or little he was, he really, truly did.

This was a right to a wrong. This was a fix. So why was it twisting him up inside?

Raph and Leo mostly seemed relieved that the whole thing was finally over, when April opened the lab door and said they were ready. Raph rubbed Donnie's head fondly, and Leo hugged him tight around the shoulders, and sensei lifted him up to brush a kiss over the top of his head. Casey bumped Donnie's arm with a gentle fist, and told him he could keep the car, and then Donnie was putting out his hands, round eyes reaching for Mikey from not that far away, and Mikey reached over automatically to lift him out of sensei's arms and hug him tight.

"I'm a little scared," Donnie whispered, all sincere, and like they weren't standing right there in front of their whole family. He gazed up at Mikey with the whole world in his eyes, and Mikey swallowed a sudden lump in his throat and smiled back.

"Don't be scared, Dee. It'll be over before you know it, and then you'll be my big bro again. And you're so good at that!" Rockwell was shifting around impatiently, probably only keeping quiet under the indomitable force of April's laser-like glare, but it made Mikey a little self-conscious anyway—and the rest of everyone was staring at him, too, so he pressed a quick kiss between his little big brother's eyes and handed him over to April. Donnie's hands lingered on his arms, holding tight for another split second or two; looking too stricken and anxious for someone just about six years old. So Mikey put all his feelings on a shelf and locked them up, and gave Donnie a wink and a playful grin. "See you soon, dude. Promise."

It worked like a charm—always did—and Donnie was finally smiling back and letting go. April tucked him into her arms like a seasoned pro, and Mikey wasn't really expecting the kiss she pressed to his cheek, or the gentle nudge Raph gave his shoulder, and then the lab door was closing on little Donnie's little wave, and Mikey stood there just staring at it long and hard.

An arm slipped around him from one side, and he blinked, glancing up and over at Leonardo.

"You aren't losing him, Mikey," his big brother said, eyes all deep and soft. Mikey sort of flinched from them, and all their warm understanding, and shrugged one shoulder.

"Guess not."

He kinda was, though.

Donnie came out looking pale and weak on his feet, but he met them with a gap-toothed smile that sent Mikey's heart soaring, and he wasn't sure which of them moved first but they all piled onto Donnie at just about the same exact time, tumbling to the floor in an ecstatic turtle pile.

"We missed you," Mikey said gleefully, and timed his hug to Raph's; pulling away when his red-banded brother did, smiling up at Donnie with honest warmth. If it were up to him, there would have definitely been way more hugging—after all, he'd had to wait an hour to see for himself that Donnie was okay, and it had been the longest hour of his life—but big Donnie wasn't the cuddlebug little Donnie was, and Mikey wasn't going to be clingy and weird about this, he wasn't going to make things awkward between them. Instead he took a big step back, and spread his arms wide, and said, "We should celebrate!"

The idea was met with a roar of approval from Casey and Raph , while April went to grab the takeout menus off kitchen counter and Leo invited the Mutanimals to stay, and Donnie…just sorta stood there, looking at Mikey with the fading footprint of a smile on his face, and something hurting in his round brown eyes.

"Everything okay, Donnie?" Casey said quietly, with a worried wrinkle in his brow. Donnie blinked, eyes darting over to their human friend, and after a moment his grin bloomed back and that limping sadness from a moment ago was banished to somewhere far away, and Mikey could breathe easy.

"Yup," Donnie said softly, "everything goes back to normal, now."

Or, you know, almost.

Because two and a half weeks later, they were ambushed in some dark alley. Bebop took a cheap shot at Donnie, and Donnie fell three stories to the ground; and then Rocksteady was charging, and Raph and Leo were too far away, Donnie was still struggling to get his feet back under him, struggling to push himself upright—

Then he met Mikey's eyes in the dark, and distress turned to horror, and he screamed, "Mikey, no!"

But Mikey was moving already, before he made any conscious decision to—not Donnie, not Donnie, please not him—reaching out with both hands and pushing Don as hard as he could out of harm's way.

Then there was crushing impact, like he was hit by a speeding truck or a subway train, and his brothers were yelling, and his head slammed into something solid, and he was gone.

Mikey woke up in the infirmary—knew it before he even knew he was awake, by the quiet hum of cooling fans and computers, the familiar smell of engine oil and hazelnut coffee—and it was such instant comfort, always was. He hadn't been in here in weeks, not since the accident that made Donnie—

Donnie.

His next breath hitched in his throat, and hands came down on his arms a second later, before he could so much as open his eyes or work himself into a proper panic.

"Shhh, easy, Mikey, it's okay."

It was soothing and certain and totally disarming, and Mikey leaned into those hands before he knew what he was doing. He knew this place, and he knew that voice, and he knew the touch of those hardened, calloused fingers against his shoulders—knew all of it was good, all of it was safe. But—Donnie. Mikey had to be sure he was okay, had to make sure, Donnie needed him. His eyelids felt like sandbags as he struggled to get them open under weighted, clinging sleep; shell, even his shell felt tired, and the soft-worn quilt draped over him might as well have been made of lead, and those strong hands weren't budging for a second.

"What happened?" he asked, or thought he did—the words all ran together, kind of like his brain was starting to. He was only barely holding onto consciousness with both hands, here, but he'd fight sleep tooth and nail because he had to know— "Where's Donnie?" Mikey tried again, desperately. "Is he okay?"

"He'll be okay when you are," came the quiet voice again, and Mikey didn't think he liked that answer. He pushed against the hands on his arms, and they only tightened there. "Mikey, please."

Well sorry, whoever, but he didn't have time to lay around and listen to weirdly elusive answers, he had a little big brother to find, and just as soon as he figured out how to make his limbs work again Mikey was outta here.

"Y'don't understand," he tried to explain, pawing uselessly at the hands that were planted like oak trees on his arms. "I gotta—I gotta go, okay? Y'gotta let me go, he needs me."

"I know. I know," and that voice was still soft but sort of broken somewhere in the middle, tight around the edges and choked—like he was crying, and Mikey didn't know much of anything right now, but he knew where he was, and he knew that voice and he knew those hands, and when he finally finally managed to drag his eyes open, he knew the round brown eyes swimming inches from his own, knew them like he knew his own name.

"Donnie," he whispered, reaching with his fingers because he couldn't quite lift his arm, and Donnie sobbed—a tiny, hiccuping little sound—and snatched Mikey's hand up in both of his.

And Mikey didn't know hearts could break like this, out of desperate relief and all the love in the whole entire world, but that's exactly what his was doing, and he gave a little tug on their hands, he had to get that kid in his arms right now.

Donnie cottoned on right away and clambered up into the little infirmary bed with him, curling around Mikey blanket and all. Mikey held him where he could with clumsy hands, blinking through tears of his own that burned and blinded him—so happy it was painful, so relieved to see him it hurt.

"'m so glad you're here," he said, and it probably didn't make sense out of context, it probably sounded all thick and childish 'cause he was crying like a baby, but he didn't care. Donnie's forehead was right up against his, his brother's octopus arms tight around his shoulders and his carapace, and for some reason, he was heavier than Mikey remembered, and a lot bigger; he didn't quite fit against Mikey the way he did before.

But it didn't matter. He was Donnie. And just for that, Mikey hugged him even closer, and loved him absolutely and forever.