AFD for short. This is when a person becomes an uber fangirl/fanboy of whatever they enjoy to the point where they are fans of everything.
Person 1: Omg! I love Harry Potter!
Person 2: OMG YEAH! And I love Twilight and Star Trek and Lord of the Rings and Pokemon and sheep and chapstick and ipods and cheese and...
Person 1: You so have Addictive Fandom Disorder.