Wally's part-time job at the radio station, KAY-HIP, and the competition of the station with the rival radio station, KAY-LOUD, causes Denver to rise to fame as a radio star.

When Heather and Wally's parents inform the two that they are expecting guests from out-of-town, they must hide Denver that the local movie theater, which is believed to be haunted.

A boy genius, Freddy Facknitts, invents a time machine that sends Denver and Morton Fizzback into the past and into the middle of a crazy caveman competition called Mammothball.