Unlike many voice actors who did most of their work for one studio, Frees worked extensively with at least nine of the major animation production companies of the 20th century: Walt Disney Studios, Warner Bros., Walter Lantz Studios, UPA, Hanna-Barbera, Filmation, Metro-Goldwyn-Mayer, DePatie-Freleng Enterprises, Jay Ward Productions, Rankin/Bass, and Ruby-Spears.