"Rebel Without A Fin"
The episode is on youtube.
Man, That's one of the episodes I really didn't care for. That one and Mutegen monster are 2 of my least favorites. Plus, I really thought the fact they kept purposely mispronouncing the villain's name over and over got tired after the 3rd time.
Personally, I loved the first 5 episodes. The epic storyline and Bebop and Rocksteady being a serious threat to the Turtles, instead of just comic releif... I just wish they didn't continue to deteriorate their intellect over the course of the show, so they were just "those dumb guys." Plus Toei had some good animation when the 3rd episode came around. They REALLY screwed up on the first one. There was even a shot with 5 Turtles.
But when it comes down to it, I loved a lot of what they did in the Archie comic version better. They had a better version of Leatherhead, as well as Screwloose and Wingnut. The cartoon just trashed Screwloose and Wingnut.