There's a secret war being waged in the homes and neighborhoods of Earth that the humans don't even know about; an eternal struggle between two great armies: the Cats and the Dogs. The film follows a Cat's plan to destroy a new vaccine, that if developed, would destroy all human allergies to Dogs, and the Dogs' efforts to stop the Cats. Specifically, it's the story of a young pup whose job it is to guard the vaccine. Other dogs include a wise older dog who watches out for him, a large friendly dog, and a small dog who serves as an electronics expert. Jeff Goldblum is the human scientist that invented the vaccine.

The electronic press kit for the film sent to media included a video showing an increasingly irate Mr. Tinkles screen-testing unsuccessfully for several famous movie roles. These scenes can be found on the special features on the DVD.

Lou:
I'm on to you, kitty, and you're in big trouble!


Russian Blue:
I think not, baby puppy. It is you who is in trouble!

Continuity: The cats test their formula successfully on Scott. But within minutes, he shows no effects when holding Lou.

Written by Milton Ager and Jack Yellen