Two words: visible erection.
(Recognised from such notorious occasions as: "Is that a banana in your pocket, or are you just glad to see me?" and "Young man....I'm flattered")
Frankly, the most annoying thing about having a penis (don't get me wrong, though - my penis is my best friend) is that it has a mind of its own. There I am, trying to concentrate, and the devilish little blighter decides to stand at attention. In public. While I'm trying to concentrate on the speech I'm giving to a class of fifty people, including some decidedly scrumptious undergraduate morsels. Oh, the mortification! Oh, the humanity!
Suffice to say, having a penis is like having one of those poodles that will wait for the most embarassing moment to start humping a guest's leg. Without any regard for your feelings in the matter.
Never a dull moment, eh?