Prequal to 2012 verse.

Mikey's door creaked open. It creaked because the hinges were rusty and the wood was old, and Donnie had watched Space Heroes with Leo instead of oiling it's hinges. Normally, Mikey would've woken right up at the noise, as any six year old ninja in training would take pride in being able to do.

But Mikey had a fever, and Mikey wore himself out crying today and Mikey didn't even shift Mr Snuggles in his arms.

Donnie crept up to Mikey's side and eyed the cast on his leg. Or, at least, the closest thing to a cast he'd been able to make. He'd wanted to get stuff for a better one, once, but he got distracted reading his science book and made a model of the solar system instead.

"I'm sorry."

Donnie bit his lip, and wondered if Mikey would wake up. He didn't think so. He hoped not. He didn't want to scare him or anything…

"I'm sorry."

He might wake Splinter up. Probably not, though. He was real tired from worrying about Mikey all day… but no one worried more than Donnie.

"S' my fault. I'm sorry for being such a bad brother. I should've… everyone else…" Deep breath. He hadn't done anything else right, he could say this to a sleeping kid

"Leo practices ninjutsu all the time so he can protect us. Raph practices lift'n weights and usin' the punching bag for hours so he can protect us." A hitch of breath. "Even you practice playing pranks and making us laugh so we all stay happy. But not me.

I get distracted and make dumb projects and watch dumb cartoons instead of doing my job.

You don't understand this, Mikey, but you might never walk right again. We don't have the right stuff to heal your leg and it might not set right. You could get an infection; we live in a sewer. You could get gangrene and we might have to cut your leg off or you could die from the infection or blood loss, if we do amputate.

And no one understands it but me. Not even Master Splinter gets it, not really. He knows some, but… but there isn't anyone else… I just wanna tell you that I'm gonna do better.

Next time I'm gonna be ready when one'a you gets hurt. I'll know what to do and I'll have the stuff I need to do it. I'm gonna be a real doctor as fast as I can so no one ever has to be in pain like you again.

And if that means I don't ever come out of my lab again, then I'll just stay there. I'm gonna do my job, Mikey. I'm gonna protect you like I'm supposed to. Like a big brother is supposed to. I'm gonna grow up and be a adult just like Master Splinter as fast as I can so I can protect you no matter what happens.

I'm gonna learn everything that could go wrong and how to fix it up again. I'll be a doctor, inventor, electrician, plumber a everything 'cause I'm the smart one and it's my job. I'll know everything so you guys don't have to.

I've got a lotta work to do, but I'll work hard on it. Only I can do it, and from now on I'm gonna do my job. I'm gonna be a grown-up, Mikey. No more playtime.