Consider
Naruto, where the main character (who is a boy) has a shapeshift technique called
Harem no Jutsu. I saw a couple of girls cosplaying as that once. They had very carefully arranged stylized little fluffy clouds on. They had a long conversation with hotel security.
I had stuff with me, so I made a badge thing that looked just like the "EXHIBITOR" badges only it said "EXHIBITIONIST" for them.
The most famous male examples, of course, are
Man Faye and
Sailor Bubba.
Mostly, though... My feeling is that people who dress up as things from a show are probably doing it because it was fun, or because they like the show, or because they wanted a costume and a friend had one that fit them, or because they want to show off their looks, or because they're trying to overcome crippling insecurity about their looks, or because they didn't even think about it and that was what was clean, or because they lost a bet, or because they won a bet, or if there's a girl involved, or if someone's paying them.