It's a slow night at a local pub in Ireland, and the owner is polishing some glasses and thinking of closing up early, when he hears a knock at the back door.
He opens it, and there in the alley are two nuns, Sister Mary and Sister Kate, both are looking up and down the alley, as if they don't want to be seen. They ask to be invited in, and the owner brings them into the kitchen.
"We've a favor to ask," explains Sister Kate. "It's not for us, you understand, but for poor Father Tim."
"He's been struck with an awful case of constipation," continues Sister Mary. "And they only thing that seems to help is a bit of whisky. Now we'd buy it ourselves, but this town being as full of gossips as it is, we don't want to start tongues to wagging."
"Now as a good, church-going man, we've come to ask if you might spare a little something for poor Father Tim, and to use your discretion in the doing of it," finishes Sister Kate.
"Of course, Sisters," replies the barman, and he returns with a full bottle of the best whisky. "Give this to Father Tim with my compliments, and my best wishes for a speedy recovery."
An hour or two passes, and the barman closes shop and drives home. As he's driving, he sees Sister Mary and Sister Kate arm-in-arm, walking down the road, and singing at the top of their lungs. Sister Mary is carrying the bottle, which has perhaps an inch left in it. He slows and rolls down the window as he brakes to a stop.
"Sisters," he says' "I'm ashamed of you. You told me the whisky was for Father Tim's constipation."
"Ah, but it is," replies Sister Mary. "We're headed that way now, and when Father Tim sees us in this condition, the man is likely to shit himself."