Real Name: Billy Bob Reilly
First Appearance: X-Force #117
Mutant Ability: Prehensile skin and body fat
Give someone the attitude of rap star Eminem and the special abilities of Mr. Fantastic and you get Phat. Growing up in a trailer park and on the streets, he was a troubled youth up until the discovery of his mutant abilities, which he eventually used to fight crime.
Oops, scratch that. His parents are actually really nice folks. The whole trailer park angle was created by the publicist to give him more of an edge.