Harold "Brain" Hellman was a criminal and convict locked up in New York, native to the John Carpenter Multiverse. He was perhaps most well-known for being involved in The Kansas City Incident. Within the confines of New York, he became very self-indulgent and very egotistical, which was only put up with by the other inmates because of his ability to create fuel.
When his old partner Snake Plissken arrived looking to rescue The President after his crash-landing in New York, Hellman was forcibly recruited to his cause. He went along with it for a pardon for himself and for Maggie, his "main squeeze". This involved betraying his current employer, the Duke of New York.
Hellman usually did not survive The Escape from New York.