Splinter explains that he was once a Japanese man named Hamato Yoshi, who was leader of an honorable ninja clan called the Foot. One day, he was framed for the attempted assassination of a visiting sensei by his rival, Oroku Saki, and banished to America. His honor forbidding him from begging or stealing to survive, Yoshi went to live in the sewer, where he befriended the rats. One day, he found a quartet of turtles by a storm drain, coated in a strange ooze. The ooze was a mutagen that caused its victims to take on the traits of the animal they’d most recently been in contact with. The turtles, most recently in contact with Yoshi, mutated into teenage turtloids. Yoshi, most recently in contact with the rats, became a rat-man. The Turtles nicknamed him “Splinter” on account of his old walking stick and he in turn named them after his favorite painters: Leonardo, Raphael, Donatello and Michelangelo. He then began training them in the art of ninjutsu.