This was inspired by Amiticia's story Generations, which is found on Stealthy Stories. It takes place right after the episode Fathers and Sons, season 5 episode 10 of the 2003 cartoon.
"…and we'll do it again. We will find a way to defeat the Tengu Shredder—all of us."
Michelangelo looked around at his brothers, still wearing those medallions with the dragon foot on them. Even though he knew better, even though it was upside down (or was it right side up and the other one was upside down?), seeing the mark of the Shredder on his brothers still gave him the creeps. He turned to the Ancient One.
"Hey, Ancient One?" he asked, earning the attention of his entire family. "I have a question."
"What is it, young one?" he said, inclining his head at the turtle.
"Well… why did we have to go back? Why… why couldn't we have stayed with you in Japan?"
"Mikey…" Leo said in a warning voice, and Michelangelo resisted the temptation to make a face. It's not that he didn't know he was being rude. He just didn't really care.
"No, it's all right, kumquat," the Ancient One said, nearly destroying Mikey's attempts at keeping a straight face. Kumquat. Snerk. The little man turned to Michelangelo and shrugged, grinning uncomfortably. "I have very bad luck with children?" he said, his tone suggesting he was not being serious. Mikey frowned.
"But we could have… we could have lived in Japan." He couldn't bring himself to say, we could have lived under the sun. The Ancient One smiled.
"Leonardo," he said, still looking at Mikey. "What is Michelangelo's greatest weakness in battle?"
Both turtles were startled by this. Leo looked apologetically at his brother before answering hesitantly.
"Well, I'd have to say it's his lack of focus. When he concentrates, he's a great warrior, but he doesn't do so nearly often enough."
"I coulda told you that," Mikey muttered.
"And would you have known that had you grown up without fighting anyone but each other or your sensei?"
"Uh…" That was a curveball. Leo thought. "I… I suppose not. Until we started battling real opponents, I guess I just thought he was a goofball through and through."
Mikey stuck out his tongue at his brother, but there was no real ire in it. He knew Leo was right.
"You see, Michelangelo," the Ancient One said. "You and your brothers needed to grow up in New York in order to become the warriors that you are. Though my home would have afforded a more pleasant childhood, it would not have made you into what you are today." He grinned again. "Plus I do have very bad luck in raising children."
Everyone laughed, including Michelangelo, but he had been around the Ancient One enough by now to tell when he was using humor to cover something up, and this was one of those times. He wondered if the old dude really thought that growing up in his house would have turned them into brother-killing maniacs, but he supposed that wasn't really the point. If he'd been given the choice, he knew he would have chosen a childhood in the sewers over one in the sun if it meant saving the world. Of course he would. That's what superheroes did.
It didn't mean he wouldn't still mourn fifteen years spent in darkness.