Mr Hong
This agetean gentleman has grown to become the Ankh-Morpork equivalent of a "cautionary urban legend", with several mentions throughout the various books (Men at Arms, Jingo, The Truth) admonishing people to "remember what happened to Mr. Hong". You see, it wasn't Mr. Hongs luckiest day when he decided that the night of the winter solstice in combination with a full moon and a lunar eclipse would be the ideal point in time and on the site of a former fish-god temple in Dagon Street the ideal point in space to open his Three Jolly Luck Take-Away Fish Bar - see there for further details.