A man gets on a bus, and ends up sitting next to a very attractive nun. Enamored with her, he asks if he can have sex with her. Naturally, she says no, and gets off the bus. The man goes to the bus driver and asks him if he knows of a way for him to have sex with the nun.
"Well," says the bus driver, "every night at 8 o'clock, she goes to the cemetery to pray. If you dress up as St Peter, I'm sure you could convince her to have sex with you."
The man decides to try it, and dresses up in his best St Peter's costume. At eight, he sees the nun and appears before her.
"Oh, Peter!" she exclaims. "Take me with you!" The man tells the nun that she must first have sex with him to prove her loyalty. The nun says yes, but tells him she prefers anal sex. Before you know it, they're getting down to it, having nasty, grunty, loud sex. After it's over, the man pulls off his St Peter's disguise.
"Ha, ha! I'm the man from the bus!"
"Ha, ha!" says the nun, removing her costume. "I'm the bus driver!"