Wear a gray suit and a white collared shirt with a red bow tie. (Pee Wee's suit had small pinstripes.)
Be sure the suit is a size or two too small. You want the sleeves and pant legs to be short. (We rolled the pant legs up to the length we wanted them and pinned them.)
Put a white hankerchief in the chest pocket of the suit. Wear white socks and white penny loafers. You'll need lots of blush on your cheeks and gel/spray your hair straight up in the front.
Be sure to tell everyone "I know you are, but what am I?"
Thanks to Mike and Amy for this great idea and photo!