A young Estella first meets Buddy when she is thrown into a dumpster by her classmates. She discovers the small puppy in the dumpster and adopts him, bringing him home with her. They quickly became best of friends and went everywhere with one another. After Estella is withdrawn from primary school, the small family travels to London to see an old friend of Catherine's. Estella and Buddy are told to stay in the car instead of going to see the gala, though their interests are piqued and they disobey Catherine and enter the gala. Buddy runs from Estella and causes a commotion, which Estella later perpetuates, and three Dalmatians chase them out of the gala. Estella grabs Buddy and lays on the ground with him while the Dalmatians barrel past them to knock Catherine off a cliff, killing her.
Estella escapes to Regent's Park where she and Buddy meet Jasper and Horace, along with their one-eyed dog Wink. The group takes refuge in an abandoned building where they remain for the rest of their young adult lives. Buddy quickly starts assisting the group of petty thieves by pickpocketing strangers, carrying wallets, and blending into situations. He walks Estella to and from work every morning, doting on her with each day. When Estella takes the moniker of Cruella, she begins to neglect Buddy and doesn't spend as much time with him. Despite this, Buddy tries to save Cruella when she is tied up by Baroness Von Hellman in an attempted murder. Buddy pulls on the ropes to untie her. He later helps her in her schemes to take down the Baroness, free an arrested Jasper and Horace, and later moves into Hell Hall alongside his companions.
- Bobby, the actor portrayed Buddy, was a stray prior to the filming of Cruella, but found a home after production finished.
- During the scene where Buddy unties Cruella, Bobby actually did succeed in untying Emma Stone, though the moment was cut from the film since John was supposed to save Cruella instead.
- Buddy is the sixth De Vil pet in Disney adaptations, the other five being Scorch and Vendella in 101 Dalmatians: The Series, Fluffy in 102 Dalmatians, Dude in the Descendants franchise and Cuddles in 101 Dalmatian Street.