Geraldo was the cousin of David Castillo, the sheriff of Swainsville, New Mexico. Growing up, he was always in some sort of trouble. He eventually ran away from Swainsville.[1]

Five years later, Geraldo was wandering through the desert when he knocked unconscious by what seemed to be a sudden violent storm. In fact, it had been caused the Flash, who had recently regained his powers after losing them during an alien invasion, only to lose control and run wildly across the country, creating a path of destruction. When Geraldo came to, he saw what he thought was the Porcupine Man, take control of the speedster. In actuality, the Flash's condition had caused spines to grow all over his body. Geraldo believed that the Flash's true spirit passed to him following this incident.[2]

He donned a Flash t-shirt and cowl and attempted to stop Tina McGee, Jerry McGee, and Mason Trollbridge, who were traveling toward Swainsville searching for the missing Flash. Despite his delusions of having inherited the speedster's powers, he was quickly dispatched by a knee to the stomach from Tina.[3]

Geraldo returned to Swainsville, where he quickly managed to offend a group of men, starting a fight. David and Jerry heard the sounds and came to investigate. In the ensuing scuffle, Geraldo managed to get his hands on David's gun, but was taken out by a hit over the head from Jerry's cane. Removing his cowl, David was saddened to see that his cousin was still down the same destructive path that he had always been on.[1] He was put into the local jail. David's son Manuel and a group of friends calling themselves the "Flash Patrol" attempted to free him, but were frightened away by Geraldo's crazed antics toward them through the window. Jerry later came by an interviewed him about his experience in the desert, hoping that it might shed some light on the Flash's whereabouts.[2]

After Manuel and his friends were reported missing, a crime for which the Porcupine Man was being blamed, Geraldo informed David that he had overheard the boys talking about exploring a nearby cave. When they arrived, they discovered that the cave had collapsed. A rescue effort was mounted, and they were eventually freed by the Flash.[4]

  • Geraldo's surname has not been given. There is a chance that it is also Castillo, if he is the son of a brother of David's father.