He attended Loyola Academy in Illinois and then graduated from the Weinberg College of Arts and Sciences at Northwestern University, where he majored in English and drew cartoons for the "Daily Northwestern". After that, he served a two-year apprenticeship with famed animator Frank Thomas, a supervising animator of Disney films such as "Peter Pan" (1953), "Lady and the Tramp" (1955), and "The Aristocats" (1970). Musker met Ron Clements during the production of "The Fox and the Hound" in 1981, where he worked as a character animator under Clements and Cliff Nordberg. Musker teamed up with Clements as story artists on "The Black Cauldron" before they were removed from the project.