Master Splinter, as he is called, is the Sensei and paternal figure of the Teenage Mutant Ninja Turtles. He is a giant anthropomorphic rat whose origin is clouded in mystery. One version of the story is that he was once a man named Hamato Yoshi. The other tale states that he was the pet rat of a ninja called Hamato Yoshi, and learned ninjutsu by mimicking the man’s training movements. He admits that both and neither are true.
Splinter is an excellent martial artist and ninja, who was forced to live in the sewers. He raised the four baby turtles when they, including Splinter, were mutated by green ooze that dripped into Splinter’s home. He named the turtles Leonardo, Donatello, Raphael and Michelangelo, after seeing names of four Renaissance artists on a book he found in the sewers. Splinter trained the turtles in the arts of ninjutsu, which is a lethal combination of physical and metaphysical expertise. Splinter has practiced the art for years, finding the balance between the light and darkness that it holds. He has been called a ninja master, but decides to spend his time in meditation more often. He prefers to read and cook, giving advice and telling stories to the turtles most of the time.
Splinter is portrayed as an elderly rat in ragged grey robes, usually remaining behind when the Turtles fight. He does not have a weapon, or uses anything as a weapon, because it is in his nature as a ninja. This does not stop him from being a skilled combatant. He is always calm and is always seen as a wise and intelligent teacher.
In TMNT, he orders Leonardo to continue training in Central America, while he and the other Turtles stay behind. When Leonardo returns to New York, Splinter tells him to find Raphael. He is voiced by Mako, or Mako Iwamatsu, which is his last film.