In 1938, Meléndez was hired by Walt Disney to work on animated short films and feature-length films such as Bambi, Fantasia, and Dumbo. While there, he worked to unionize the rank and file animators he was working with. A member of the Screen Cartoonists' Guild, he left as part of the 1941 Disney animators' strike and never returned as an employee.
Three years later, he joined Leon Schlesinger's team at the Warner Brothers studios, where, as a member of the Bob Clampett, Art Davis and Robert McKimson units, he animated on a number of Bugs Bunny, Porky Pig and Daffy Duck shorts (as "J.C. Melendez"). UPA put him on their payroll in 1948 to work on many television commercials, as well as the Gerald McBoing-Boing and Madeline shorts.
Bill Meléndez Productions
After a decade at two smaller production houses, Meléndez founded his own production company in 1964. Bill Melendez Productions helped produce the annually broadcast Christmas special A Charlie Brown Christmas, for which he won an Emmy Award and the George Foster Peabody Award despite having to work on short notice and with a tight budget. Meléndez performed the voice of Snoopy, who normally in the specials does not talk. Melendez was the only animator authorized to work on Charles Schultz's Peanuts characters.
Meléndez went on to do over 75 half-hour Peanuts specials, including the 1989 miniseries This is America, Charlie Brown, as well as four feature-length motion pictures – all with partner Lee Mendelson.