A few years ago my old man was diagnosed as being diabetic. He has a sweet tooth so I found a selection of diabetic friendly sweets and chocolate for his birthday that year.
Anyway, the next morning he called to say that he'd been up all night after shafting the bed and sitting on the bog for most of the morning with a "brown flame" exiting his anus.
It turns out that if you read the wrapper, diabetic chocolate "may" cause laxative effects if it isn't eaten sparingly.
The daft bugger had only scoffed the lot and couldn't extinguish the "brown flame" for a couple of days and many pairs of pants.
Why was your dad "shafting" the bed