The life of Coop Burtonburger is turned upside down when his spoilt little sister brings home a mysterious stray cat. Coop quickly discovers that Kat is a super-smart mastermind with diabolical plans, and realises that only he can expose the ferocious feline and save the world!

Coop can no longer go into Old Lady Munson's yard; conditioning collar.

Coop and Dennis build a tree fort to get some Kat and little sister-free time, but Kat tricks them into leaving the fort and she takes over, using all the Kat defenses they so cleverly installed to keep the boys from reclaiming their fort. Millie sells a record number of Greenie Girl Cookies but the boxes keep disappearing and all fingers point to Coop.

After Kat learns X-Rays of him were taken on his first trip to the vet, he sneaks back to destroy them. Coop follows, determined to see what Kat has to hide.

Animated adventures of a ten-year-old boy who is constantly at war with a megalomaniacal sphinx cat.

Kat's new wind up mouse has a hypnotic effect on the other cats in the neighborhood and Kat is more than happy to use it to create his own cat army! Coop convinces Dad that he's allergic to Kat so Dad will get rid of the pesky feline for good. Kat turns the tables on him, convincing Dad that he's allergic to Coop as well.