The Emperor's New School S01E01 - Rabbit Face

Kuzco faces his first threat of losing his position as emperor when he struggles in P.E. and his teacher threatens to flunk him if he can't win a race with Kronk. However, Principal Amzy (who is really Yzma) tells Kronk to turn Kuzco into a turtle so he has no chance of beating Kronk, but instead, Kronk gives Kuzco the wrong potion and he ends up as a rabbit.