This particular man was taking a shortcut through the graveyard one dark night. That was a mistake, because the gravediggers had just opened a new site, in preparations for a funeral early the next morning.
The unfortunate man took a headlong plunge into the deep pit. It began to rain, and the sides became slippery, besides being deep. Try as he may (and he did again and again) he could not climb out. Finally he resigned himself to wait for the caretakers the next morning, and he settled into a corner.
Just before dawn another man, who had been "out on the town" all night and who was definitely inebriated, stumbled into the same grave. He yelped and started trying his best to get back topside.
After a few attempts, this deep voice from the corner said, "It's no use. You can't get out!"