That's not necessarily the case - look at Slash. He's a mutated turtle of a slightly different breed (a snapper), and apart from a few spikes on his shell and a mouthful of sharp teeth - and, uh, the fact that he's crazy - he's basically the same as the TMNT. (I know, I know - in the Archie series, he was really an alien. But he originated as a mutant in the cartoon, so that's how I'm going to refer to him.)