heehee... how secure is he? How about a costume just like yours? 2 Tinkerbells?
Another idea that has light clothing would be a shipwreck survivor... normal shorts and t, but torn up abit, and a prop like a swim ring (from the SS Minnow or Titanic, eg.... or! A wilson volleyball!)... he wouldn't have to shave or brush his hair beforehand!
hmm, any Napoleon Dynamite fans? tshirts with "Vote for Pedro", big 80's glasses...and those pants that velcro'd close at the waist.
Or a group dressed in blue shorts, red/white striped shorts with terrytowel wristbands and head bands--the Globe Trotters.... maybe an inflatable basketball or one of those mini basketball+hoops as a prop.
(Dang... think my age is showing in some of these ideas....long live the 70's and 80's!

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My costume last year was simply a black tshirt and black capris with Disney "words" mis-spelled written all over (in diff colour puffy paints, glow in the dark paints, etc).... And a beauty pageant sash over it "Miss Spelt"
(eg.... Days he ducked. Dawn All Duct.)....more of a game than a costume.... The CMs had a great time with it! Got me a few extra handfuls of candy at more than 1 stand!