The next day it came to me. Since this was my daughter's first year of not wearing a girly costume, she was a little worried that girls wouldn't like her. (If I haven't ever mentioned I mostly hate girls.) So I thought her daddy matching with her would be a great confidence boost.
So I made him a Double Trouble Skylander Costume. Its a paper bag tiki mask.
I also made a scepter for him. I think this might have been his favorite part, but I can't tell you for sure, because we never discussed it.
P.S. My costume is BEYOND unflattering! :)