X-Pac, real name Sean Waltman, is a professional wrestler. Raised in Minneapolis, Minnesota, he first wrestled for independent leagues in that area. He got his first big break when he was picked up by the WWF in 1993. Known simply as "The Kid" at first, he appeared as a jobber and got his ass kicked regularly by various wrestlers for a few weeks. Then, on an early episode of Monday Night Raw, he quite unexpectedly beat Razor Ramon after performing a moonsault. It was quite unheard of for a jobber to win any sort of match whatsoever, and the live crowd went absolutely bonkers as a result--it remains one of the most shocking things ever seen on Raw.
Waltman became known as the "1-2-3 Kid" as a result of his unexpected 1-2-3 victory over Razor, and established himself as a midcard babyface for a few years. He turned heel eventually and took on Ted DiBiase as a manager, but failed to really move up in the card any--probably the only reason he continued to be pushed at all was because he was a member of The Clique, which pretty much controlled most of the WWF's booking during this time period.
A series of concussions Waltman suffered in 1995 and 1996 led the WWF to release him in '96, after which time he prompty showed up in World Championship Wrestling and joined the nWo. He was dubbed Syxx--as in the "Syxxth" member of the nWo, which is chock full of silliness because he was in reality the seventh member.
After suffering a few more concussions in WCW, he was let go in early 1998--after which the WWF inexplicably decided to re-sign him, dub him X-Pac, have him join HHH in the new DeGeneration X, and push him to the moon yet again.
Rumors began to surface in mid-2000 that Waltman had weaseled his way onto the WWF's booking committee, which would explain why he continues to be pushed despite absolutely no fan reaction whatsoever, and often wins feuds when the crowd is positively begging for the other wrestler to win.