A fake fan is a fan of a band/artist who think's they know everything about a band, but in all honesty, only found out about them 10 minutes ago and is most likely following a fad and has only heard a hand full of songs and knows nothing about the band. Fake fans tend to get aggressive when you confront them about their fakeness. They are most related to Jonas Brothers and other popular teen stars.
"oh so who's your favourite member of the band?"
"Oh you know...the one with the long hair? he's cute"
"umm, fake fan much?"
"NO I'M FUCKING NOT. I'M A MUCH BETTER FAN THAN YOU, BITCH."