After Garner had been working about six months, she auditioned for the voice of Minnie Mouse at the studio's sound stage, then located on Melrose Avenue. Because Minnie was to play a Mexican in the upcoming film The Cactus Kid, Burt Gillett had asked the Ink and Paint department, which was entirely women, if anyone could speak Spanish. Only Garner and another woman responded, and when the other woman was unwilling to sing, Garner was cast for the role. She went on to voice Minnie in more than 40 films over a decade. Occasionally Garner also provided additional voices, such as cat meows (Three Orphan Kittens, Lend a Paw), dog barking, and crowd noises.
She is the voice behind several small roles in some of the Silly Symphonies playing a mermaid and a bunny and a laughing mouse. Her voice was used in the 2013 short film Get a Horse as a Minnie Mouse.