Pluto first appeared as Mickey Mouse’s dog in the 1930 cartoon The Chain Gang.
The short was released on September 5, 1930. Pluto was initially shown as one of the unnamed bloodhounds pursuing Mickey after his escape from prison. In that first appearance, he was not yet clearly established as Mickey’s personal pet.
The character returned soon afterward in The Picnic, released in 1930, where he was presented more recognizably as Mickey’s dog. His name became Pluto, and later cartoons developed his expressive reactions, loyalty, curiosity, and frequent misadventures without giving him spoken dialogue.
Pluto is distinct from Goofy. Disney treats Pluto as a pet dog who normally walks on four legs, while Goofy is a talking, human-like dog character. Pluto’s name also coincided with the 1930 discovery of the astronomical body later called Pluto, although the cartoon character’s naming history is usually discussed separately from the planet’s discovery.