What was Pluto’s first theatrical cartoon appearance?

Pluto’s first theatrical cartoon appearance was The Chain Gang.

Released in 1930, The Chain Gang is a Mickey Mouse short set around a prison escape. A bloodhound appears as one of the tracking dogs pursuing Mickey, and that early canine character developed into Pluto in subsequent Disney cartoons.

Pluto’s identity was not fully settled immediately. The dog appeared in early stories under changing circumstances and names before the familiar name Pluto became established. His design, expressive behavior, and silent physical comedy eventually made him one of Disney’s most popular animal characters.

The short is sometimes confused with later cartoons in which Pluto is clearly identified and treated as Mickey’s pet. The Chain Gang is important because it marks the character’s first theatrical appearance, while later films refined his relationship with Mickey and his personality.