Well the King's daughter was into her mid twenties, and the king didn't want his princess to be an old maid. The princess wasn't the most beautiful of women, and wasn't having any luck finding a suitable husband. The King finally decided to take matters into his own hand.
He had flyers printed up and posted all over the kingdom, "who so ever wishes to marry the princess should appear at the castle at noon, the following Sunday."
Only three suitors arrived at the castle. The king decided to have a test to determine who would get his daughter's hand. Each suitor would have to climb the castle wall, swim the moat, and then have sex with one of the castle's cows.
The first suitor didn't even make it over the wall. The second suitor made it over the wall, but couldn't swim the moat. The third suitor, climbed the wall, swam the moat, fucked the cow, and wasn't even tired. The king went up to him, and said "Congratulations, you are the only one worthy enough to marry my daughter." And the suitor replied, "Forget your daughter, I want your cow!"