Rocksteady and Bebop were originally regular human members from a gang of thugs until Shredder made them his henchmen. To make them more powerful and to test his mutant serum, Shredder had a rhino and a wild boar stolen from the local zoo and their genes were mixed with Bebop and Rocksteady's. Despite being mutant human/animal hybrids, the two aren't very smart.
Although in this version of the Turtles, Rocksteady is an enemy, his character was likely influenced by the Usagi Yojimbo character Murakami Gennosuke.
Appearances Throughout Comics
Rocksteady in most early comics was shown to be burly with a bit of a pot belly. But recently he is now shown now to be very muscular before and after mutation and much smarter (not much) than his early counterpart.
Along with his best friend Bebop, Rocksteady was chosen for mutation by Karai after she stole mutagen from Krang on Burnow Island. During the City Fall storyline, Karai appears with the two brutes as the Shredder and the Foot Clan are under a surprise attack by the Turtles and their allies. They quickly turn the tables against the Turtles as Rocksteady easily over powers them taking a sai to his arm as if nothing happened. He soon suffers an invisible attack that drives him through a wall. At the end of the fight, Rocksteady and Bebop are blasted with a grenade by Old Hob.
Vs. The Turtles and the Mutanimals
Later, Rocksteady and Bebop meet Pigeon Pete whom tells them about the mutant army his boss Old Hob is putting together. The two brutes decide to check it out once they hear that "turtles" are a part of the gang. They then decide to smash open an ATM machine to buy some food before the fight.
They later come across Old Hob and the Turtles; before a fight can break out Old Hob attempts to reason with them by stating that they're only slaves to Shredder. Old Hob changes his mind about them joining when they reveal themselves to be half-human. Hob responds by shooting Rocksteady in the face and Bebop in the stomach, thus the fight begins. Rocksteady holds his own and even helps over powers the two teams. He matches Slash in strength and easily swats Mondo Gecko against a wall with his sledgehammer. He sends a car flying with a single blow and removes Slash from the battle in the process. Next he dispatches Leonardo with a single kick, and then throws Raphael and Alopex on top of a building taking them out of the fight as well.
Rocksteady is dead set on killing Old Hob until Splinter intervenes hitting him and Bebop in sensitive areas. Together with his partner they suffer being electrocuted and is later beaten by a building being collapsed on them. They then leave when they see everyone has left, and Rocksteady asks Bebop to keep their defeat a secret from Karai, in which he agrees to do.
Attack on Technodrome
The Shredder enters into an alliance with Donatello to attack the Technodrome realizing that Krang is the greatest threat to his one day rule of the planet. However, he doesn't trust Donatello completely, therefore before departing to Burnow Island to confront Krang and his forces. He leaves Rocksteady and Bebop on a special mission to watch over Donatello, warning the Turtle he will have his two henchmen kill him at the first sign of treachery.
On Burnow Island, Shredder's forces are immediately ambushed, and he engages into a death battle with Krang. Bloody and facing certain death, Krang reveals to Shredder that he was betrayed. Later, he issues the orders to Rocksteady and Bebop to kill Donatello. The fight is rather brief as Rocksteady lands a clean hit with his sledgehammer to Donatello's body. He then engages Metal Head in battle and heavily damages the robot. While Bebop struggles with Donatello, Rocksteady lands the crippling blow to the Turtle, bashing him across his back with the sledgehammer and smashing his shell. Rocksteady and Bebop then walk away leaving the Turtle for dead, as they receive new orders from Karai.
Rocksteady is very skilled with heavy weapons such as the M-60. He is very strong and his fighting style seems to be brawling as he takes heavy swings at most of his enemies.
Rocksteady is immensely strong and is capable of taking on the entire Turtles team. He carries a sledgehammer and uses his strength for a big advantage. He's a street fighter and is very vicious in a fight. He won't hesitate to use deadly force to kill his enemies. For example, once the opportunity presented itself, he immediately attacked Donatello with his sledgehammer and crippled the Turtle by smashing his shell. So far, Rocksteady appears to be stronger than Bebop. He's able to match Slash in strength and hurl cars with single punches. He is also very durable being able to withstand being shot at close range in the face, take Leonardo's katana blade slices across his arm, shrug off stabbings in the shoulder by Raphael, survive an electrical attack, missile attack, and even a building being dropped on him.
Rocksteady seems think he is on friendly terms with Shredder, but sometimes appears afraid of him. He and Bebop are best friends and are usually never seen not together. He hates the turtles especially Raphael for beating him and Bebop in a fight. He seems to enjoy working for the foot clan, and tolerates their members.