Geldoff was orphaned and by the age of 13 he moved to America. He was constantly picked on by the rest of his school. It was during a party two years later that Geldoff got drunk and revealed his ability by blowing up cars as entertainment for the students there until the police arrived. His principal took him and the students from the football team as punishment. Geldoff used his power to blow up the principal's car which attracted the police once more. Spider-Man arrived to investigate but decided to leave Geldoff to the police, although Geldoff grabbed onto him as he swung away. Spider-Man had a conversation with Geldoff trying to teach him that great power comes with great responsibility and discovered that Geldoff was phobic about being a possible mutant. When the conversation turned sour Shadowcat, Marvel Girl and Storm came to take him to Professor X and he fainted twice. Geldoff regained consciousness on the X-jet and blew it up nearly killing those on board. The X-Men managed to get him to the professor who revealed that Geldoff was experimented on while inside the womb and is registered as neither human or mutant by Cerebro. When Xavier revealed his plans to hand over Geldoff to some science organizations and expose evidence of the experiments, Spider-Man attempted to break him free under the intention of letting him live a normal life but was unable to get past Xavier's psychic powers.
Geldoff's current whereabouts are unknown.