you used to be a regular little turtle, chillin in a little patch of moss under a drainpipe in some random New York alleyway. One night, while on patrol, Raph caught a glimpse of you munching on moss as he was jumping from rooftop to rooftop. He thought you were super cute, and despite the emotional backstabbing from Spike, and him currently caring for Chompy, he decided to take you back to the swewers with him.

So here you were, crawling around Donatello's lab with Chompy, living your little turtle lives.. until a beaker of mutagen fell off the table you were crawling under.. mutating you..