The Great Wise Man
Leonardo is one of the main characters of the Teenage Mutant Ninja Turtles cartoon series, originally created to accompany the promotion of the toy series of the same name released in the 1980s (themselves inspired by a comic book that had gone fairly unnoticed at first). The Ninja Turtles are mutant turtles living in the sewers of New York City and fighting crime with the help of their sensei, a mutant rat named Splinter. Leonardo, named after Leonardo da Vinci, is the closest of the ninjas to his sensei and the one who takes his training the most seriously. He spends most of his free time training and meditating and follows a strict code of honor that he urges his brothers to follow as often as possible.