One funny prison story could be about an inmate who tried to start a prison band. He managed to make instruments out of whatever he could find in the prison. A guitar from an old wooden box, drums from buckets. Despite the strict prison rules, he got permission to have a little concert for the inmates, which brought some much - needed laughter and entertainment to the otherwise dull prison life.
There was a story about a new inmate who was very scared on his first day. He accidentally walked into the wrong cell and sat on someone else's bed. The owner of the bed, instead of getting mad, started making jokes about how the new guy was already trying to steal his territory. It broke the ice and soon they all became friends. This simple incident brought some comedy to the prison environment which is often seen as a tough and unforgiving place.
It's a matter of debate. Some believe there might be some elements of truth in the King Arthur story, but it's likely highly embellished and fictionalized over time.