St. Peter meets Mother Theresa at the Gates Of Heaven and says, "You were 
a good woman. I'm giving you a nice halo."
Mother Theresa is walking around Heaven when she sees Princess Di, and the 
Princess has a much bigger halo.
Mother Theresa goes back to St. Peter and says, "St. Peter, I spent most 
of my adult life helping the poor and the sickly. Princess Di did no where 
near the amount of charitable work I did. Why does she have a bigger 
halo?"
St. Peter says, "That's not a halo. That's a steering wheel."