Two nuns driving home midnight at Hallowe'en when suddenly a hideous little devil starts leering at them from the grille.
"Tis the Divil hisself", says Sister Mary-Patrick of the Holy Crucifixion in a strong Irish brogue. "What shall we do?"
"I dunno", says Sister Theresa-Helena of the Blessed Shroud in an even stronger Irish brogue. "Show him your cross".
So Sister Mary-Patrick of the Holy Crucifixion winds down the window and shouts:
"Oi, you! Fuck off!"