Rocksteady was a normal "punk" on the street until Shredder took him and Bebop in and then mutated him into a giant Rhino. As one of Shredder's henchmen, Rocksteady doesn't need much of a brain and a good thing that is for he really doesn't. But even with that he is smarter than Bebop. Shredder uses Rocksteady to go out and use absolute brute force to try and manhandle the Turtles. He may be defeated fight after fight by the turtles, he still is a challenging foe.