Trama

After a policeman and his police dog are fused together to turn into Dog Man, he must stop the villainous Petey the Cat from cloning himself and creating an evil kitten, doubling his evil abilities.

Petey the evil cat terrorizes OK city and has come up with a plan to use a bomb to destroy a building and Knights the cop and his dog Greg arrive, only for the bomb to explode, ultimately injuring them both. The doctors decide to put Greg's head on Knights body and create a human-dog hybrid which they name Dog Man.

Unfortunately, Knights girlfriend dumps him and his house is sold, leaving him to stay at the police station. Dog Man takes his favorite tennis ball with him. Dog Man constantly stops Petey in his tracks, after a bunch of jailbreaks, earning him the respect of the townsfolk. This quickly escalates into a full on rivalry between Dog Man and Petey.

Petey comes to the realization that he needs to clone himself in order to beat Dog Man, so he uses a cloning machine. Unfortunately, Petey doesn't read the instructions for the machine and has instead created a small version in his likeness. Little Petey is too innocent so Petey abandons him, only for him to be picked up by a little girl, who he unintentionally offends and she too disowns him, with nowhere to go, until he is adopted by Dog Man.

Petey now plans to revive a dead once super villain fish named Flippy to help him out. Petey is about to use telekinesis to revive Flippy, when he discovers a picture book drawn and left behind by Little Petey. This fills Petey with immense guilt and he goes to find Little Petey. Petey takes Little Petey back and uses him as bait for Dog Man. In doing so, Petey explains to Little Petey that his father too had abandoned him as a kitten and Little Petey decides to use Peteys 80-HD to find Peteys father and reconcile the pair. Unfortunately, Peteys father still hasn't changed and is still not very nice and he refuses the offer. Petey decides he no longer needs his father's support and goes to fight Dog Man.

Flippy gets reincarnated at the Living Spray factory and starts laying waste all over OK city and brings all the buildings in town to life, using the Living Spray. Whilst Dog Man and Petey are battling each other, Flippy takes Little Petey and quickly flees from the scene. Dog Man and Petey team up in the hope of rescuing Little Petey from Flippys grasp. They all fight each other and the buildings and Flippy is about to drop Petey into a volcano and Dog Man sacrifices his tennis ball to save Peteys life. Little Petey manages to talk to Flippy and helps Flippy to renounce his evil ways, using a picture denoting the pair as friends.

Flippy gets arrested and Petey is pardoned for all his good deeds. Petey and Little Petey return to the lair to discover that Peteys dad took everything except for Little Peteys drawings. Petey and Dog Man vow to share custody of Little Petey and the trio, along with all of their friends throw a celebration party in the town.