In an embellished version of 'Jack And the Beanstalk', Denver buys some magic corn kernels off Morton Fizzback, which are thrown into the ground and grow into a giant cornstalk, which Denver climbs to find the giantess of the castle (Bertha Bird).

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.