He had other small parts until a secondary, but more prominent role in the 1935 serial The Adventures of Rex and Rinty. That same year, Levine gave Autry his first starring role in the 12-part serial The Phantom Empire, with Burnette playing Oscar, a comic-relief role. Mascot was soon absorbed by Republic Pictures, and Republic enjoyed enormous success with its musical Western features starring Autry. In each of the films, Burnette played Autry's comic sidekick, Frog Millhouse, with his trademark floppy black hat and trick voice (imitating a deep, froglike croak). Their association produced 62 feature-length musical Westerns.