The Lone Wanderer was a fat man, who came out of the vault in search of food.
For some reason, he hung around in the vault for ages killing the security guards and looting their stuff. He left the vault carrying more in his Misc Tab than anyone had ever done before. It is a well known fact he is so alone because he smells like ass.
He found Megaton, but found nothing except a black cowboy sheriff there. The search continued for this man but soon ended when he tried to befriend a super mutant and was eaten soon after.