Donatello earns his degree from Sopho University, but discovers that he has been mistaken for a girl, so he asks Irma to masquerade as him. Meanwhile, the real Donatello discovers a plot by Professor Philo Sopho to destroy the Earth.

A professor's new ray-gun causes plants to go wild and his pet ape Jocko to become a giant rampaging monkey. By using the same ray-gun, Donatello is increased to Jocko's size so he can fight the giant ape and save April from him