Topical costumes are always appreciated, and this one is low-hanging fruit. Mask, complete with gap-toothed grin? Check. Pin-striped jacket? Check. Pants around the ankles, in a not-so-subtle nod to his recent on-air announcement that he had conducted affairs with members of his staff? Why, you must be late-night wisecracker David Letterman! Bonus points if you can convince a friend to grow a goatee and tag along as Letterman's alleged blackmailer, Joe Halderman.