FAN!CRACK 

Any object pertaining to one's fandom to which one can become extremely addicted to. In other words, anything equivalent to a cocaine addiction, but for a fan. Term is usually associated with fangirls and followed by the word ttly in capital letters.

Biggles: I loff David Tennant! Simply cannot wait until Doctor Who Series 2 comes out on DVD January 16th!
Me: Yeah, meh too! Say, did you know the extras include a David Tennant personal video diary?
Biggles: O RLY?!
Me: YA RLY!
Biggles: O.O NO WAI! OMGZ!
Me: IT'S UTTER FAN!CRACK !!!! *squee*
Biggles: TTLY! XD *seizure*

FAN!CRACK by quixoticpenseuse December 9, 2008

Fan Crack 

Refers to random humor partaining to a particular show/movie/book that often makes no sense to people outside the fandom. The thought behind the term is that one would have to be on crack to think up some of the jokes. Also extremely adictive (Ex: "crack breeds crack")

Can come in the form of fanfiction, fanart, photo edits, etc, etc.

The fan crack destroys my brain cells... in a happy way.

Fan Crack by Firien March 30, 2005