Everyone has their own intepretations of a character
Can you spot the second Poison Ivy in this pic? We saw ten, TEN, at Comic Con. If you dress up as a popular character, you are probably going to run into someone else who has chosen that character. Respect their style choices. (Fourth Doctor versus Tenth Doctor comment debate, GO!)
You also might find that no one recognizes you. "I have some costumes where I get recognized once and I'm really psyched!" Said Indie.