A hippie gets onto a bus and proceeds to sit next to a Nun in the 
front seat.  The Hippie looks over and asks the Nun if she would have sex 
with him.  The Nun surprised by the question politely declines and gets 
off at the next stop.

When the bus starts on it's way the guy driving the bus says to the 
hippie, "If you want I can tell you how you can get that nun to have sex with 
you." The hippie of course says that he'd love to know so the bus driver 
tells him that the every Tuesday evening at midnight the nun goes to the 
cemetary to pray to the lord. "If you went dressed in robes and some glowing 
powder," said the bus driver guy, "you could tell her you were God and command
her to have sex with you."

Well the Hippie decides to try this out.  So that Tuesday he goes to 
the cemetary and waits for the nun.  And right on schedule the nun shows 
up. When she's in the middle of praying the hippie walks out from hiding, 
in robes and glowing with a mask of god.  "I am God, I have heard your 
prayers and I will answer them but you must have sex with me first."

The nun agrees but asks for anal sex so she might keep her virginity. 
The hippie agrees to this and quickly sets about to go to work on the nun.

After the Hippie finishes, he rips off his mask and shouts out, "Ha 
ha, I'm the hippie!!" The nun replied by whipping off her mask and shouting,
"Ha ha, I'm the bus driver!!"