During high school, he worked a summer job at an ice cream shop near the Walt Disney Studio.

[5]In 1927, Clark began working the Monday after he graduated high school for a temporary position,[5][6] first as a camera operator and later as an ink and paint artist.

[7] At the time, the studio were finishing the Alice Comedies and starting work on Oswald the Lucky Rabbit.

Iwerks mainly animated the first Mickey Mouse cartoons Plane Crazy (1928), The Gallopin' Gaucho (1928), and Steamboat Willie (1928) in which Clark worked as an inbetweener.

[12] On the Silly Symphony short The Goddess of Spring (1934), Clark used his sister Marceil as a reference model for the character Persephone.

Andreas Deja complimented Clark's animation, writing it is "charming, as it chugs along to an energetic musical beat through a landscape that is reminiscent of a children's illustration.

"[21] For Song of the South (1946), Clark handled the animation interacting with Uncle Remus (portrayed by James Baskett) during the "Zip-a-Dee-Doo-Dah" musical number.

[22] On Cinderella (1950), Clark animated the title character, sharing the role with Eric Larson and Marc Davis.

[27] He made his feature directorial debut with Sleeping Beauty (1959), in which he directed the opening scene in which the townspeople arrive at the castle for Aurora's christening.

[24] During the late 1930s, Clark met Miriam Lauritzen, a set decorator and model, who had a son Richard from a previous marriage.