Star Wars Kid
In 2002, a Canadian high school student made a video of himself swinging a golf ball retriever around like a Star Wars lightsaber.
Some of his classmates found the tape he made, and posted it online. The student was, of course, totally humilated. (Which is, of course, SUPPOSED to happen when your high school classmates find a video of you acting totally retarded.)
The video went viral and became an internet sensation. Those who had video editing skills added titles, music and special effects, and posted their efforts. The student was so tormented that he dropped out of school and his family sued the families of the students who first posted the video online.
Since then the video has been parodied on South Park, American Dad, Arrested Development, and even by comedian Stephen Colbert.
The video was one of the most popular videos on the Internet in 2003, and as of 2007, had been viewed almost 1 billion times.
There have been many versions of this video since - this is one of the better adaptations: