There was one mother who wore this lovely Italian Ren dress. It was just gorgeous. Turns out she does Ren Faire, so it's not a surprise. Some of the other parents wore costumes - my sister-in-law did - but many either just work a witch's hat or just regular clothes.
And one kid - oh my goodness.
It was a store-bought costume. Toon!Robin. But. His candy "bag" was a plastic Batman head. It was perfect.