Master Splinter

Splinter is a fictional, wise, and elderly mutant rat who is the adoptive father and sensei of the Teenage Mutant Ninja Turtles. He trains them in ninjutsu to fight the Foot Clan and their leader, the Shredder. He was once a normal human named Hamato Yoshi. After his family was destroyed by his stepbrother, Hamato Yoshi fled to New York City and bought four pet turtles. During an encounter with the Krang, both he and the turtles were exposed to mutagenic ooze, mutating them instantly. Yoshi became a giant rat, while the turtles became humanoid. He is a master of ninjutsu and uses various ninja weapons, often wielding a cane with a sword and has a long-standing rivalry with the Shredder (Oroku Saki), who was once his rival in the Hamato Clan. He is typically portrayed as grave, stoic, and wise, but fiercely protective of his sons Leonardo, Donatello, Raphael, and Michelangelo.