His enemies include the Joker's hyenas Bud and Lou, the Penguin's trained birds (Artie the Puffin, Griff the Vulture, and Waddles the Penguin), and Catwoman's pet cat Isis (who flirts with Ace much like Catwoman flirts with Batman).
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.
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They both also appear in Batman: Arkham City where The Penguin has them killed and stuffed in his museum as an exhibit prior to the events of the game.
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