The inmates at an Irish prison didn't have enough free time to repeat the same long jokes, so they gave them numbers.
Every of the seasoned inmates knew the jokes the numbers represented by heart, and it saved on a lot of time telling jokes.
The system worked.
One day, a new inmate joined, and was flabbergasted when he saw the group of men taking turns shouting numbers.
"Number twenty-three!" shouted one guy. The crowd erupted in laughter.
"Forty-seven!" roared another one. The crowd cheered and howled.
"What are they doing?" asked the new guy to his cellmate. He explained the system.
"Oh," says the newcomer. "Let me try." He clears his throat and croaks "Sixty-four!"
The entire crowd goes quiet, everyone stares at him oddly.
"Was that not a good joke?" he whispered to his cellmate.
"Oh, no, it's one of my favourites, but you told it wrong."
"OK" he said, "I'll try another one."
He shouted robustly "Ninety-two!"
And the whole prison erupted into Laughter.
He said to his cellmate "That must be a terrific joke, everyone loves it!"
"I'll say!" said the other, wiping a tear from his eyes "Haven't heard that one before!"