On the way to his apartment, Yoshi bumped in to a man. Sensing something odd about him, he followed him and found himself infront of a meeting between the Kraang. The Kraang attacked, but he defeated them. A canister full of a strange ooze hit Yoshi and turtles, giving the turtles human-like characteristics and turning Yoshi in to and antromorphic rat.
He took the name the turtles gave him, Splinter, and taught ninjutsu for self-protection of the outside world. He gave the names of four Renaissance artist: Leonardo, Michelangelo, Donatello and Raphael.