This is one of my favorite jokes ever, so I hope it doesn't lose a lot in the written form:
Sean is a young man in Ireland attending Sunday Mass and also going to confession. Sean sits down in the confessional and says to the priest,
"Oy, Bless me Father, I have sinned."
"Sean, my son, what is your sin?"
"Father I have been with a loose woman."
"Faith and Begora Sean, who was the woman?"
"Father, I cannot tell you."
"Was it Colleen O'Riley?"
"Was it Fional McFly?"
"Was it Bridget Shaughsseny?"
"Sean, I see that you're not going to tell me who the woman was, but
you have sinned and for that you must atone. Say 12 Hail Marys and
I don't want to see you in my church for 3 weeks."
Sean goes back to the pew and his friend Colin slides over.
"Oy, Sean, what happened?"
"Oy, I got 3 weeks vacation and 3 good leads!"