Leeroy Jenkins is easily the most recognizable name in all World of Warcraft. It isn't Thrall, it isn't Arthas, it isn't Chris Metzen or Ghostcrawler. It's Leeroy Jenkins. Leeroy has transcended the realm of geekdom in a way that no other aspect of World of Warcraft can.
While World of Warcraft may have made appearances in shows such as Stargate Atlantis, Leeroy has found a place on How I Met Your Mother, My Name is Earl, Scrubs, and beyond -- he has become a genre and a trope unto himself. Leeroy Jenkins has been mentioned and plugged so many times in pop culture that the days of his being a World of Warcraft reference are in decline and we're coming to a point that most of the world has no idea of the origin of the joke. It's just a funny thing that exists, disembodied from its nerdy, video game roots.
So who is this Leeroy Jenkins fellow, and why is he so gosh-darn funny?