In which 1930 short did Pluto first appear under the name Rover?

Pluto first appeared under the name Rover in the 1930 short The Picnic.

In The Picnic, the dog accompanies Minnie Mouse and is presented as her pet rather than as Mickey Mouse’s familiar companion. The character’s identity and ownership changed during the early cartoons before Pluto became firmly established as Mickey’s dog.

Pluto had appeared in an earlier 1930 cartoon, The Chain Gang, but that appearance did not yet give him the name and role audiences would later associate with him. The Picnic is therefore important in tracing the character’s early development.

The name Rover can cause confusion because Pluto’s early appearances were not fully consistent. Later Disney shorts settled on Pluto, and the character became one of Mickey’s closest friends, known for expressive pantomime rather than spoken dialogue.