While working underground to fix a water main, Brooklyn plumbers—and brothers—Mario and Luigi are transported down a mysterious pipe and wander into a magical new world. But when the brothers are separated, Mario embarks on an epic quest to find Luigi.

Buster and his new cast now have their sights set on debuting a new show at the Crystal Tower Theater in glamorous Redshore City. But with no connections, he and his singers must sneak into the Crystal Entertainment offices, run by the ruthless wolf mogul Jimmy Crystal, where the gang pitches the ridiculous idea of casting the lion rock legend Clay Calloway in their show. Buster must embark on a quest to find the now-isolated Clay and persuade him to return to the stage.

A slick New York publicist who picks up a ringing receiver in a phone booth is told that if he hangs up, he'll be killed... and the little red light from a laser rifle sight is proof that the caller isn't kidding.