When movie star Phil Grey (Peter Gallagher) does a production of Oliver with boys only, 12-year-old Christi (Allison Smith) disguises herself as a boy to get into the show.

Karen (voiced by Nancy Cartwright) and Andy (voiced by Robbie Lee) are accidentally transported back to the year 100,000,000 B.C. in their father's time machine. Trapped in the Age of Dinosaurs, the kids confront surly cavemen and are also rescued from a pterosaur by a lovable, orange-haired creature with an inflatable trunk named Bunjee (voiced by Frank Welker).

Karen and Andy return to the modern world with Bunjee, who is hardly ready for civilization and soon a couple of Bunjee eggs hatch into pure prehistoric pandemonium.