As he approached lights out in his first night in prison, the man was getting more and more nervous. Finally the lights turned off and the officers left the tier, leaving him alone with his cellie.
The cellie went to the bars and a few seconds later someone a few cells down yelled "36!". There were a few chuckles. The cellie yelled "14!" and there were a few laughs.
Finally the new guy said "OK, what's going on?". The cellie said "we've all been here so long, we know each other's jokes. We gave them all numbers to save time".
After a few more numbers, some funnier than others, the new guy asked, "can I try?". "Sure" the cellie responded.
The new guy yells "97!'. All of a sudden, everyone is laughing, banging on the bars, his cellie is crying, he's laughing so hard.
New guy says "what happened?!". The cellie, wiping tears from his eyes, says "oh man, we'd never heard that one before!".
Alternative ending 1: The new guy yells "97", and there's no response at all. He looks back at his cellie with confusion on his face, and the cellie just says a disappointed "some people just cannot tell a joke..."
Alternative ending 2: The new guy yells "97", and there's an audible gasp. He turns to his cellie in confusion, and the cellie just slaps him across the face, saying "I can't believe I'm sharing my cell with a god-damn racist!"