Teenage Mutant Ninja Turtles (1987): Season 10, Episode 2

10 - 2: The Beginning of the End

While Raphael, Michelangelo, Donatello and Carter work on restoring Leonardo to his regular self, Mung steals all the plutonium from a power plant in order for Dregg to build a Plutonium Ray to turn Leonardo into a radioactive killer.