Traveling salesman stops at a hillbilly farmhouse to sell some wares. While
he's there a fierce storm comes up, and the farmer invites him to spend the
night.
However, as there wasn't a spare bedroom, the salesman would have to sleep in
the same room as the farmer's daughter--on the condition that if any hanky-panky
went on and the daughter got pregnant, the salesman would have to marry her.
The salesman eyes the daughter, who has the body of a goddess but the head of
a javelina, and figures out that he's being set up for a shotgun wedding. But he
didn't want to brave the night's storm, so he agreed to the farmer's terms.
The next morning, the family is sitting around the breakfast table. The
father asks the daughter, "Did he do it last night, girl?"
"Sure did, Pa."
"Excellent!" says the father. "If it's a boy, we'll call him John." "And if
it's a girl," says the mother, "we'll call her Martha."
About that time the salesman came into the room holding a condom and
grinning. "Well," he says, "if the little bastard gets out of this, we'll call
him Houdini."