While the Chipmunks are working at the amusement park, Majestic Movie Studios, in a singing attraction. Little do they know that the real Dr. Frankenstein are in a new attraction called, "Frankenstein's Castle". After Alvin drives a crazy bus ride, they miss their next performance and get locked in the park after closing time. Dr. Frankenstein figures that the castle isn't scary enough and re-creates the real Frankenstein and after the monster finds the boys, it starts a wild and wacky adventure...