Memes

It's the exact same phenomenon that several other fandoms or belief groups have gone through. First, start a satirical society and laugh about the foolishness with boon companions. Enjoy the companionship. Second, expand so that the society doesn't die when you leave college or the location. Begin recruiting folks and telling them about your society. Third, watch as people join and some don't realize it's satirical. Disbelief dawns on the originals. Fourth, the true believers take over as the people in on the joke slowly leave due to all sorts of reasons, including no longer finding the society funny because of the true believers.

I watched it happen with bronies (not the furry sexual folks, 4chan already had those, but just people who were really, really into the show) on 4chan, a 'drinking' club at my college that was a joke because they only drank water at the meetings (at first, anyway), and a local activity (can't name it because it's specific and would give it away) club that was truly supposed to be just a social gathering but is now populated by a gaggle of 70 year old women fervently taking part.