the problem with girls costumes are that young girls are constantly pressured (or is it encouraged?) to be as sexy as they can as soon as they can. look at the 6-10 tv programming and the toys like the bratz dolls. if the sexy nurse or sexy fairy sells well in the 6-10 crowd you're gonna see more of it.

and i mentioned ironman... batman is more recent and more likely to stick in kids/parents minds better.

as for the joker, i am soooo tempted to go for it but the problem is that i am a semi-neurotic perfectionist that will go to great (insane) lengths to looks as close to the character as possible.
not just tricking out some thrift store clothes and slapping on make up, but reshaping the hair line, using liquid latex or something to make scars and other facial features (mah forehead does not wrinkle), developing the personality (no too hard), the whole nine yards.
so the joker costume is up in the air for me.

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I can tell the difference between punks who need a little lesson in manners... and the freaks like you who would just enjoy it.

look i has 'art' (updated randomly) - http://captaindesertpirate.deviantart.com/