The world ends and all the nuns are lining up outside heaven. St. Peter stands in front of their line and says "If you have ever touched a mans private parts just wash them in the fountain and go in." The nuns start to go in with the occasional few washing their hands. Suddenly one of the nuns charges to the front pushing the others out of the way. St. Peter asked her what she was doing, to which she replied "Im going to wash my mouth before sister Mary comes to wash her ass"