Krang is working on duplicating the original mutagen when Bebop and Rocksteady come in and screw it up. A fly lands in the mutagen and it increases in size. Not being able to control it, Bebop and Rocksteady send the giant insect to Earth. After seeing what the mutagen does to the fly, Krang and Shredder decide to use it to create large insects to take over the world.
Genghis Frog (a friend of the Turtles) decides to go to the city and see his buddies. Upon getting there, he spots the huge fly and starts chasing it. Meanwhile, the Turtles are watching TV and they see April's report about the massive fly. The TMNT go to check it out and end up rescuing Genghis from the huge bug.
In Dimension X, Krang and Shredder use the mutagen on three bugs and send them to Earth to keep the Turtles busy while they move ahead with their plan. Their scheme is to find an anthill and use the mutagen on the ants.
The city is going nuts with the giant insects running amok and destroying it. A mud wasp is b