The Merry Pranksters [Catillac Cats] Heathcliff & the Catillac Cats : Season 1 Episode 64

Leroy gets a new assistant dog in the junkyard and announces that tougher rules will now be enforced. The new dog is the world's worst practical joker and makes our heroes suffer unmercifully until Riff Raff discovers that the new dog can dish it out, but he can't take it.