In 1955, Deitch took an apprenticeship at the animation studio United Productions of America (UPA), and later became the creative director of Terrytoons, creating such characters as Sidney the Elephant, Gaston Le Crayon, Tom Terrific, and Clint Clobber. Beginning in 1955, while working at UPA, Deitch wrote and drew the United Feature Syndicate comic strip "The Real-Great Adventures of Terr’ble Thompson!, Hero of History", starring a courageous child in fantastical adventures. A skit about Terr'ble Thompson had been recorded by Little Golden Records, with actor Art Carney and bandleader Mitch Miller participating. That led to the daily strip, which ran from Sunday, October 16, 1955, to April 14, 1956. In early 1958, his theatrical cartoon "Sidney's Family Tree" was nominated for an Academy Award. In August 1958, he was fired from Terrytoons and set up his own studio in New York called Gene Deitch Associates, Inc., which primarily produced television commercials.