one of my favourite religious jokes was told regularly by singer, Joe Heaney

A Protestant married a Catholic girl on the understanding that he would take up her religion - they were married in church
One Friday, shortly after the wedding, the priest was cycling pat their cottage whe he caught the smell of frying meat
drifting through the window - he propped up his bike and walked into the house, to find the man tucking into a large steak
He reminded him of his promise, which forbade him eating meat on a Friday
"But I only eat meat father, up to now that's never been a problem"
"Well, replied the priest, "Whenever you feel the urge for meat on a Friday in future you must only eat fish; try repeating "I'm a Catholic, I'm a Catholic"
I'll try father
A few Fridays after he was passing the house again when he caught the same smell - frying meat again
He stormed through the door to find the man in front of a steak saying, "You're a fish, you're a fish"
Jim