Okay, now that I've read the horse joke, I am astonished at all of you (and John Tierney, who wrote an op-ed in the NYT and is probably related to me). This is not a sophisticated joke about horse phalluses, or subtle reference to bestiality. This is a plain old city slicker comes to the country joke; they are as old as cities. Country people raise animals, remember? Animals are notoriously bad at observing anyone's rules about appropriateness of sexual behavior or genital display other than their own. Which is why city folk neuter their dogs.