Gym Gems is a 1926 Felix the Cat short produced by Pat Sullivan.
Plot[]
Felix, driven by hunger, emulates a goat by trying to eat a shoe. Failing this, his next attempt at eating focuses on a bucket of poster glue, resulting in him getting tangled up in a poster advertising milk.
Finally, Felix wanders into a boxer's training camp and becomes a factor in his training or unwitting simulation with the boxer himself. He earns the enmity of this person who becomes so angry that Felix fears for his life. The cat is knocked off the field by this boxer, which angers Felix so much that he decides to take revenge.
Felix enlists the help of a mule and takes it to the training camp. After the fight, the cat takes pleasure in acting as referee, counting to ten over the prostrate body of the "boxer".