Splinter

Splinter was once a human named Hamato Yoshi, a brilliant martial artist and a member of the Foot Clan. He was betrayed by his friend Oroku Saki, who later became the Shredder. After being defeated by Saki, Hamato Yoshi was left for dead in the sewers. He was found by a group of rats, who took him in and nursed him back to health. Over time, Hamato Yoshi began to take on the characteristics of the rats, and he eventually became an anthropomorphic rat himself. He took the name Splinter, and he became the father figure to four orphaned turtles who he found in the sewers. Splinter taught the turtles the ways of the martial arts, and he helped them to become the Teenage Mutant Ninja Turtles.