It's okay to say "dick" except when you mean "penis"

The other night on The Daily Show, John Stewart was talking about exchanging recipes for spotted dick with the British (or something - I wasn't completely paying attention). ANYway, he goes on to say "My recipe for spotted dick involves a Sharpie ... [pause] ... and my *beep*." To me, the funniest part about the whole thing wasn't the pun, but the fact that he'd said the word "dick" two or three times prior to that last one, and that was fine, but when he used it to mean "penis," the censors had to step in to protect us.

I wonder if a similar rule would apply to discussions about titmice? For instance, if one suggested that a titmouse is a mouse sitting on a *beep*. Huh. I guess it does.