Sayonara's post about mating for large willie size reminded me of this
Somewhere, sometime, there was a man who decides that it's time to marry, but wants his bride to be pure and unspoiled by the world. So, much like Diogenes and his search for an honest man, he went on an epic quest for a pure woman. As a test, he would drop his shorts and ask, "What's this?" Invariably, the response would be, "That's your willie!" at which point he would move on to the next candidate.
One day, though, the answer was, "I don't know." He knew this was the woman he should marry, and did so. On their wedding night, he asked again, "What's this?" And the response again was, "I don't know." At which point he informed his new bride, "This my dear, is a willie." Whereupon she burst out laughing. "Be serious! Willies are black and about three times bigger!"
or, alternately:
Q: What's white and 12 inches long?
A: Nothing