A prank involving the system on a conventional flushing toilet (invented by Sir Thomas Harrington). The prankster performs a bowel movement into the top of a toilet (rather than the bowl). The next unfortunate user witnesses faeces gush forth (whilst of course expecting water) when flushing said toilet.
God damn it Leroy - did you set up this East-African Chocolate Flush?
The East-African Chocolate Flush is a horrible prank.