Origin of xD

[Rengori]

Where did xD come from? I admit it's not a terribly difficult smiley to discover on your own, but I always thought that xD originated at this site. I wasn't much of an internet savvy when I came here (still probably not), but I did not even see a hint of xD until I came here, where it ran rampant. Wikipedia says that it came from an episode of South Park, but I am unfamiliar with the episode.

I immediately thought of South Park when someone explained to me that it was a laughing face, because that's just how their faces look like o.o

Only for like one episode.

And also according to Wikipedia, xD is the model of the car, which is awesome but probably not intentionally named after our beloved emoticon.