The Three Holes
This guy was really sleepy and needed a place to stay for the night. So he sees this barn up the road and asks the guy if he can stay in his barn for the night.
"Sure," says the farmer, "as long as you promise not to stick your winky into the three holes." The man promises, and the farmer leaves him there. Of course, he can't resist, and the farmer is woken up in the middle of the night by screams coming from the barn. The farmer goes down and finds the guy stuck in the third hole.
"What are in these holes?" the guy screams.
"Well," says the farmer, "one of them's my daughter, one's my cow, and one of them's an automatic milking machine that doesn't stop until it gets five gallons."