The Burtonburgers face friends, neighbours, and each other in a local Fishing Derby.

When Millie tickles Mr. Kat's 'tickle spot' he goes into a blissful state that renders him useless as an alien agent and when Kat's empire find out about him they send a robot to destroy Millie.

Kat builds a Rat-ray gun, which he plans on using to turn Coop into a rat, but Dad gets zapped instead, so Coop hopes he can change Dad back... If he can catch him first!

Coop breaks every window in Dennis' house, and is forced to work off his debt by working in Henry's store.

Coop and Kat fight over the animal's new lightning box generator and end up swapping brains.

When Kat is fired for incompetence the Robo-Kat-Kops that are sent to take him home also capture Coop, Dennis, Fiona, Millie, Lorne, and Harley and take them to the Kat Planet.

Coop and the rest of the kids need Kat's help to escape Kat Planet. Will he give it?