Big Name Fan

A Big Name Fan, commonly called a BNF, is someone who, while not officially associated with South Park Studios is still widely known in the South Park fan community.
Maybe the BNF created a fan website that has become the source for information on South Park. Maybe they created a South Park Fanfiction or other amateur derivative work that is so well-done, everyone in the fandom has seen it. Regardless, everyone in the fandom now knows their name... or at least their Internet handle. 
This can get a little weird for some BNFs, who often still think of themselves as "just another fan." Some will let it go to their heads (even before they've truly hit the big time), some will freak out, some will just take it in stride. 
The recognition is great, but remember that being a celebrity is overrated: BNFs are easy targets, and are often singled out for torment by jealous fans. This may extend to their friends. Thankfully, the anonymity factor helps their life from getting too crazy: the vast majority of BNFs today did whatever they became famous for on the Internet while older ones did so through fanzines and mail, so their faces (and/or real names) are often unknown to most, making them indeed just another fan in the real world (even if they're gods on the Net). 
Commonly, BNFs might start off a popular Fanon idea, be a pillar of stability, and so forth.
Category:Terminology