Something the Anonymous have taken as a symbol of anonymity, is the Guy Fawkes mask. It is a mask used to hide the identity (and the ruined face of the main character called V) in the movie V for Vendetta.
If you see a person, walking around in a Green Man Suit, combined with a costume (and a tie ofcourse!) like nothing, you can draw a conclusion that he has something some kind of connection with the chan sites.
Chanblog - Anon has already defined a chan person, an Anonymous HERE, but not how they look like IRL
If a person is ugly, fat, unwashed and wierd, you know that he hangs around at chan sites.