I don’t often dress up for RPGs, but when I do, it’s for some entertaining reason. One time I had just recently acquired an awesome steampunk belt and managed to justify it as “appropriate” for a zombie apocalypse* in a fantasy setting. I mean, really, who WOULDN’T make any excuse to wear this thing?
Another time I got my character sheet, read through it, and started mussing my hair and tearing up tiny little pieces of paper and sticking them on my head. People were confused. The GM was even a little confused–she had given me a character who had been cursed with extremely bad luck (the character didn’t realize she was actually cursed), but couldn’t figure out for the life of her what I was doing.
When we started, and my character stumbled into the bar where the scene was taking place, I stared at the patrons/PCs already there with wild eyes and said, “My god, you people have some particularly aggressive pigeons around here! Is there anyplace I can was the crap out of my hair?”
Cue everyone trying to hold in their laughter and not break character.
*Actually, they were crazy people, not zombies, and it only lasted for 6 months. . . .