Dame Nellie Melba was infamous about, um, exercising her throat with cute stagehands during a show.
http://www.network54.com/Forum/172914/thread/1248649068/bjs+and+the+voce....+yes+i+did+a+search+but+have+more+questions
Norman Wisdom leading the crowd in a rendition of Sussex By The Sea rewritten by himself.
Repercussions to this day as some still sing 'going up to win the cup'.