Farmer's first job, at the age of 15, involved doing voices, especially those of Western stars like John Wayne or Walter Brennan. He and his friends would sometimes go through fast food drive-thrus and order foods in his voices. In college, he found work in radio and TV and then moved on to stand-up comedy as an impressionist until he moved out to Hollywood where he voiced Goofy since 1986.
During his stand-up years, Farmer worked at a comedy club called the Comedy Corner in Dallas. Tuesday nights were open mike nights there and he had just taken a job at an electronics store. He had just recently stopped working in show business and radio and he missed his audience. So he went to the club on Tuesday nights and he created his own five-minute routine. Starting on March 16, 1982, he started going to the Comedy Corner every week and started working on his routine and it became a career inside of six months. He worked at the Comedy Corner from 1982 until he moved to California in 1986.
Farmer's decision to move to California came from a Dallas commercial agent who suggested that, given his talent for voices, he should try his luck in California. He was recently married, but he and his wife talked it over and came to an arrangement. She stayed back in Dallas while he commuted for a year after he got an apartment. Then four months after his moving out to Hollywood, his agent asked him if he could do any Disney characters. His very first animated character audition was for Goofy. When he auditioned for the voice, he studied all the cartoons with Goofy in them, especially the ones released in the 1930s. He studied the hilarious laugh and the distinctive "gawrsh". He inherited the voice of Goofy (as well as Pluto and Horace Horsecollar), around the same time Tony Anselmo inherited Donald Duck, and Wayne Allwine and Russi Taylor did likewise for Mickey and Minnie Mouse, respectively. Bill believes that cartoon voices are not about funny voices, but rather acting. His mentor was the late Daws Butler, the voice behind many of the old Hanna-Barbera characters. Daws put it in Bill's mind that when doing cartoon voices, you're not merely doing a funny voice, you're an actor and the acting is premier and that you have to think like the character you're doing and he is also best known as the voice of Goofy in A Goofy Movie in 1995 and as the voice of Goofy in the sequel An Extremely Goofy Movie in 2000.