Sparky is forbidden to join Timmy at the cinema and other places. Timmy wishes for Sparky to become human so they can go together. At first, Sparky loves being a human; entering the cinema to view movies and eating chocolate. Jorgen changes Timmy into a dog to take Sparky's place due to the deficiency in the dog community, but Timmy wants to be human. He has only a limited time to find Sparky. Only 7 hours - of dog hours which means only one hour! How will he find Sparky in time, considering as a dog he is not allowed into certain places.
The Dimmsdale Demolition Derby forbids dogs and 4 legged beings [and things too] from entering. Even the Dimmsdale dog park forbids dogs! So Timmy mopes that his magical dog named Sparky cannot join him. Wanting to spend more time with Sparky, Timmy wishes for Sparky to be human. Now Sparky wears blue pants with a yellow shirt which is decorated with a white star.
Unfortunately for Timmy, they still cannot be together because he must do homework while Sparky goes out having fun. When he comes home, he raves about how wondrous it is to be a human being--then he throws up on Timmy's homework after pigging out on chocolates, a privilege dogs are not able to experience.
Seeing that he could not spend as much time with Sparky, Timmy wishes that Sparky was a dog again. Unfortunately, Cosmo and Wanda are unable to grant the wish because they could not interfere with true love, and Sparky was in love with being human; in order for them to turn Sparky back to normal, Sparky would need to agree to it first. To make matters worse, Jorgen Von Strangle appears and tells Timmy that by making Sparky a human, he has caused a mess in the human-dog continuum, and the only way to fix it is if Timmy takes Sparky's place as a dog, which is said in Da Rules. Now transformed into a dog, Timmy is given an hour to convince Sparky to become a dog again or else he would stay as a dog forever.
Cosmo, Wanda, Poof, and Timmy then poof to the Dimmsdale Demolition Derby. Unfortunately, they land in the demolition course rather than the audience bleachers, where several cars are dangerously targeting them. Cosmo and Wanda then poof to Sparky who is sitting in the stadium and inform him of what has become of Timmy. Feeling terrible for Timmy, Sparky agrees to become a dog again--after all, it was so uncomfortable to wear clothes. However, before Cosmo and Wanda are able to reverse the wish, Doug Dimmadome comes and grabs Timmy by the scruff of his neck, commenting that dogs were not allowed (yet again). Luckily, Mr. Turner got lost while driving and somehow ended up in the derby. Not wanting to hit a dining table which Cosmo poofed up during the panic, he swerves and hits Doug Dimmadome instead. With Doug Dimmadome out of the way, Timmy wishes for Sparky to be a dog again.