@davep's shaggy dog story reminded me of my childhood friend Endel, who when we were fifteen once told a joke that went on for the best part of an hour. We'd left his house, caught a bus and walked to school in that time.
The joke wandered along but was centered around 'the Purple Doctor'. Any noun associated with them was also purple, so the Purple Doctor would go to the purple desk, open a purple drawer and take out their purple stethoscope... you get the picture.
Each of the Purple Doctor's patients dies in increasingly horrible ways. One of them has an autopsy, which the Purple Doctor performs (removing their purple organs one by one) etc etc.
As time went on I began to get fractious but Endel was clearly enjoying himself immensely and kept reassuring me that we were almost at the punchline. Eventually we ended up huddled under cover from the rain, late for class, and STILL the joke continued as yet another purple patient bit the dust.
Finally I'd had enough and proclaimed "Come on man, I'm running out of patience!"
...and Endel leapt up and yelled "SO'S THE PURPLE DOCTOR!"
FIN



