Otto James Messmer was an American animator known for his work on the Felix the Cat cartoons and comic strip produced by the Pat Sullivan studio.

Felix the Cat is a cartoon character created in 1919 by Pat Sullivan and Otto Messmer during the silent film era. An anthropomorphic young black cat with white eyes, a black body, and a giant grin, he is often considered one of the most recognized cartoon characters in history. Felix was the first fully realized animal character in the history of American film animation.