I made the hat from a cereal box, covered in upside-down pleather from from last year's costume and decorated with, among other things, feathers from 2008's flapper costume. The shirt was also from the Prince costume, and worked perfectly.
David told me he'd overheard someone who didn't know me well ask, "Who's the Hatter?" I was indignant that someone wouldn't recognize my character--until David pointed out that the person recognized the character easily, but didn't know me. After the past few years' somewhat obscure costumes, it was fun to be such an easily recognized character.