That's what Lore Sjoberg thinks
Right now, I have two pieces of, well let's charitably call it evidence. First, Penn Jillette. If anyone was going to make up a dirty joke, then fool millions of people into thinking it's a super-secret comedian thing, it would be Jillette. Secondly, I can't find any evidence that it was posted to the Web or any other section of the Internet before 2001.
The second part of that is somewhat persuasive, actually.
Wikipedia has a lot of background information
on the joke, as well as a link to the filthy, filthy South Park
version. (via Cynical-C
: Or not