Bud and Lou are fictional characters, the pet hyenas of The Joker on the cartoon series Krypto the Superdog, in which the Joker himself never appeared. They are primarily the foes of Ace the Bat-Hound, the pet of Batman, and were first introduced in the episode "The Dark Hound Strikes!" They attempt to commit crimes for their master, requiring Ace and Krypto (and Streaky the Supercat, on occasion) to stop them. Their names are references to the comedy duo Abbott and Costello.