Frank Oliver was a native of Australia who was extremely fascinated with kangaroos. He would spend his vacations studying them and yearned for the ability to run and leap like they did. Eventually he decided to train alongside them. He would eat what they ate and go where they went. He achieved the ability to jump and box like his marsupial role-models. He decided to try and cash in on his new abilities by entering into boxing matches. However he was too fierce and on one occasion almost killed a man. He decided to leave the country before the police caught up to him and reached America. However the authorities apprehended him for not having a passport and tried to deport him. But he managed to escape and adopted the identity of the Kangaroo.
He needed money and noticed two guards carrying an important case. Unfortunately he had no idea that the case contained a jar of deadly bacteria. He managed to steal it away despite the opposition of the guards. However when the Kangaroo opened up the case he was surprised to see a strange vial, which he thought contained jewels. He put it in his pocket so he could cash it later. His robbery had made the news and Spider-Man decided to apprehend the criminal before he caused a plague upon Manhattan. After a brutal conflict, Spider-Man managed to retrieve the vial but the Kangaroo had escaped.
Months later, the Kangaroo met up with a man called Jonas Harrow. He performed a series of operations on him which resulted in the Kangaroo obtaining enhanced powers. He decided to seek revenge on Spider-Man but during the battle he kept on hearing a voice in his head telling him to steal radioactive isotopes. Dr. Harrow had implanted a small metal pacemaker that was partially embedded under his skin. As long as that was there, Oliver had no choice but to follow his orders. Oliver broke into a special lab on the Hudson River but was being pursued by Spider-Man. Despite Spider-Man’s warnings about concentrated gamma rays, the Kangaroo still attempted to steal the isotopes. He was immediately killed by the heat.