Nun on the bus
A guy is riding the bus. When the bus pulls up to a stop, the most beautiful woman he has ever seen gets on. The only problem is that she is a nun. He decides to approach her anyway.
"Sister, you are the most beautiful woman I've ever seen, and I must have sex with you," he says.
"I'm sorry but I've given my body to God," she replies, and then keeps walking.
Suddenly, the bus driver turns around to the guy and says, "I know a way you can get her in the sack." The bus driver tells the guy about how the nun goes to confessional every day, at 3 PM.
The next day at 3 PM, the guy is in the confessional booth, dressed as a priest. When the nun approaches in the darkness, he says "Sister, God has told me I must have sex with you."
She replies "Well, if God has said it, we must do it. However, because of my strong commitment to God, I will only take it up my rear-end." The guy figures this isn't a problem, and proceeds to have the best sex he's ever had.
After it is over, he whips off his outfit and says, "Surprise! I'm the guy on the bus."
Then, the nun turns around and says, "Surprise! I'm the bus driver."