The Teenage Mutant Ninja Turtles started out as a parody. And like so many other things that had unintended consequences such as potato chips which were meant to be an insult to a diner that complained that his fried potatoes were too thick chips and the turtles became huge.
Comic books, video games, cartoons, movies and toys...just about everyone knows the four reptilian heroes that were named after Renaissance artists: Leonardo, Donatello, Raphael and Michelangelo.
Of course, the creators of the Teenage Mutant Ninja Turtles missed an opportunity to make them a quintet, because they overlooked the possibility of Sandro. Ottorino Respighi didn't ignore Sandro; in fact, he wrote a musical tribute to Sandro's 3 greatest paintings.