My mother was ill with cancer and this is the joke my father told:
A doctor moved in next door and this old biddy used to keep asking him for diagnosis over the fence (What should I take for this? What do I do for That?) and so on. The doctor died and within a few days the old biddy died too and was buried next him. One day the doctor heard a knock, knock on his coffin and it was the old biddy wanting to know what to do for WORMS!!!!
I thought my Father's timing was a bit off, though i never doubted his sense of humour.