Samurai Jack

Jack bumps into an old wizard who transforms him into a chicken - a rather goofy-looking master of the martial arts that nobody can understand. He gets captured and taken to a animal fight where he must defeat a robot beetle and snake. Jack wins but must then fight a spider-like creature, a giant worm, and the ratlike mechanical "Finisher". Jack's series of wins make his new owner a wealthy man but when he goes out to buy some decent clothing he bumps into the same wizard who hits them both with a spell - causing Jack to become human and the owner to become a chicken. Jack departs with a new found appreciation for the virtues of not eating chicken.