Happy Days S01E04 - Guess Who's Coming to Visit

With Potsie's parents out of town for the weekend, he's staying with the Cunningham's, much to Howard's displeasure. The first night he's there, the boys learn that a classmate challenged Fonzie to a drag race in Ralph's newly suped car. When Howard discovers what the boys are up to, he goes down to where the race is taking place, and is soon picked up with the kids by the cops.