It seems to me that humour is everybody's way of keeping sane and standing off from the situations so that they can see it intellectually, as well as emotionally, and I don't know whether you've noticed, but if somebody tells a joke, it's nearly always a mini fantasy.
“Always I pay. Always I pay. How do you know Gelli? What do you want? How much do you want?”
“The point is, how do you know the Guarantee Fairy isn't a crazy glue sniffer.”