I dressed up for Halloween once by saying, "I am a ninja, see? I blend in so well." and going in my normal clothes. It worked, because not everyone at the place was dressed up. :P

I don't think I'd do well with cosplaying, though it does sound fun. I mostly just want to make myself a werewolf costume. It is very much an idea that will likely never be more than thought about. But I do have fun seeing the wonderful stuff being made. It's awesome.