The Simpsons are concerned with Santa's Little Helper's behavior. He digs a hole in the backyard, he has seemingly endless energy, and disobeys commands. A pet store clerk suggests that they buy new toys for the dog. On the drive home from the pet store, Santa's Little Helper jumps out of the car. The Simpsons eventually find him at the dog track mating with a female greyhound. Marge takes the new dog into their home, and not long afterwords, they have a litter of 25 puppies.

Small and playful at first, the puppies soon drive the family crazy. Depite Bart and Lisa's protests, Homer and Marge decide to give them away and put a sign in front of the house, advertising free puppies. Mr. Burns shows up wanting them all, but Marge is suspicious and refuses to give the puppies to him. With Smithers' help, Burns steals the dogs.

Bart and Lisa sneak into Burns' estate and overhear his plans to make a tuxedo out of the puppies. As they are escaping with the puppies down the laudry chute, Burns intercepts them. Aware that Burns has a particular fondness for one of the puppies, Bart and Lisa foil his attempt to separate it from the group. Burns realizes how special all the puppies are. He raises them as racing dogs and earns millions of dollars in winnings.