Professor Willard W. Willard, one of Donatello's idols, invents a Molecular Intensifier to control the growth of living things. Krang hears about it and sends Shredder to steal it. While testing the Intensifier, the Professor accidentally zaps his pet monkey Jocko, who grows to 30 feet in height. He also zaps some roots which then grow enormous and begin to take over the city, turning it into a jungle. Jocko gets attracted to April and starts chasing after her. To stop Jocko, the Professor zaps Donatello, making him 30 feet tall as well. Jocko gets angry at Donatello and they start fighting. The Turtles realize they have to stop Jocko before he and Donatello destroy the city. They urge the Professor to come up with a formula to reverse the Intensifier's effects. The Turtles finally reverse the Intensifier's effects. They stop Shredder from getting the device and return the City back to normal. (thetvdb.com)