The family dog, Santa’s Little Helper, begins behaving strangely. He digs holes in the backyard, has seemingly endless amounts of energy, and disobeys verbal commands. The Simpsons go shopping at a local pet store and, on the advice of the store’s owner, buy new toys for their dog. But the shopping spree has little effect: on the drive home, Santa’s Little Helper jumps out of the car. The family visits all of the dog’s favorite places, but to no avail. Finally, Lisa suggests checking the place where Homer and Bart found the dog—the race track. Homer cannot resist the opportunity; he places a bet on a race. But as the family watches from the stands, Santa’s Little Helper jumps into the race and couples with a female greyhound. Marge realizes the dog is in love. She takes the other dog, She’s the Fastest, into her home. Not long afterward, She’s the Fastest gives birth to 25 puppies.

At first, the puppies are small and playful enough that the family cannot help but be charmed by them. But the novelty soon wears off, and the animals become an inconvenience. Homer and Marge realize that the puppies must be given away. Despite the protests of Bart and Lisa, Homer and Marge advertise they are giving away the animals for free. Mr. Burns arrives at the house and offers to take all the dogs away. Marge is suspicious of his motives and declines the offer. But with Smithers’ help, Burns steals the puppies.

Realizing that Burns is the culprit, Bart and Lisa sneak onto his estate. When they overhear Burns’ plans to manufacture a tuxedo using puppy hides, Bart and Lisa organize a rescue attempt. They push the puppies down a laundry chute that leads to a basement. But Burns, armed with a shotgun, corners them. Bart and Lisa, aware that Burns is particularly fond of one puppy named Little Monty, foil his attempt to separate his favorite dog from the group. Burns realizes how special all the puppies really are. He raises them as racing dogs and reaps millions of dollars in winnings.