The kids need Denver out of the way while they prepare a surprise birthday party for their dino-pal. But dino-sitter Freddy Facknitts gets them both into trouble when his "space ship" puts Dr. Funt, who thinks he is an alien from outer space, on their tail.

Denver is put through his paces, participating in an exercise program with the kids while trying to hide a mischievous baby gorilla.