The highlight of young Billy's summer is spending time with his uncle, Professor Will, the greatest inventor in the world, and entering the Crazy Invention of the Year competition. This year's theme is Robopets, and Billy has a great idea: they could model their creation on the professor's cute red mongrel, Ketchup.

Best friends Maxx and Darsey are fascinated by a planet far, far away on the other side of the galaxy, and when the chance arises to stow away on an exploratory mission, they cannot resist a trip to planet Earth