Instigator
Banned
And it is a freaking Gameboy green game!
The game had big characters and was fairly well animated, certainly for the Gameboy standards at the time. The game had some parallax scrolling, another oddity on the portable. But probably better was the soundtrack, a pumping collection of familiar tunes and new ones. I loved it.
The moves were basic, barely qualifying as a beat-em-up, but it offered some platforming on top of that. I really liked the way the game was faithful to the characters in the cartoon. Schredder and Krang were my favorite bosses. My only complaint is that is that it was over so quickly!
One last thing I loved about this title are the hidden bonus game, especially the little mind teaser against Krang, trying not to end up with the last piece. I remember combing through every nook and cranny of all levels to get access to those bonuses.