The Kamek of Super Mario World is the young Bowser's caretaker. Upon learning that two babies who have just been born are destined to be problematic to the future King Koopa, Kamek tries to kidnap them, but is thwarted by the Yoshis. During the game, Kamek has his toadies always on call to capture Baby Mario if a Yoshi leaves him alone for long enough, and shows up personally on his flying broom to make the bosses grow in size. I guess he and Rita Repulsa must have gone to the same school of villainy. When he shows up in later games, it's usually as Bowser's right-hand turtle. The Paper Mario games bring in Kammy Koopa, sort of a female equivalent of Kamek, as Bowser's main assistant. I wonder if the two of them are related.
By the way, bethje says that Kamek, as he appears in Yoshi's Island, looks like Scooter from the Muppet Babies. I guess I can see that.