Sister Mary Margaret enters O'Flynn's liquor shop.
"I'd like to buy a bottle of Irish whiskey", she tells O'Flynn.
The owner of the store shakes his head and frowns. "A bottle of Irish whiskey? And you being a nun, too!"
"Oh, no, no," Sister Mary Margaret exclaims. "It's for Father Reilly. His constipation, you know."
O'Flynn smiles, nods and puts a bottle into a bag. Sister Mary Margaret pays, takes the bag and goes on her way.
Later that day, O'Flynn closes shop for the day. On his way home he passes an alley. There in the alley is Sister Mary Margaret. She's rip roaring drunk, the empty bottle at her feet.
"Sister!" O'Flynn scolds. "And you said it was for Father Reilly's constipation!"
"It ish," answers Sister Mary Margaret. "When he shees me, he'sh gonna sh**!"