Charleston has not been very forthright about his life. At some point in his past, some wild dogs let him live and he has waking nightmares about them. The only thing that is currently known for sure is that he was orphaned at a young age and was passed around foster homes until he was apprehended while trying to sneak into a secure site, at which point he was paired with Subject M.
Once they began living together, Charleston began to blossom and become more acclimated to other people and society, though he still had a keen interest in the supernatural. This almost got him into trouble several times, and while he tried to bury his impulse to go after the supernatural during a period where M was gone, he returned to this with full force upon being reunited with M.
Shortly after being reunited, Charleston was captured by an alien woman named J who later freed him and became his roommate. Charleston was very uncomfortable during this arrangment. He is also currently legally dead.
Charleston has sometimes shown remarkable durability and strength.