That was Eastman and Laird's doing, I don't think they liked classic Bebop and Rocksteady very much. And after seeing a lot the old show...I can see why. Bebop and Rocksteady were practically super soldiers, yet they were barely a threat! Tokka and Rahzar were even DUMBER than them, yet they OWNED the turtles, so much that they felt the need to retromutagenize them! Did they do that in the 87 show? I don't think so, too much effort to change too little.