Actually Susan Stroman spoke about "Break a Leg" on The Producers DVD commentary. She said that "The audience claps so loud that you have to take a deeper bow at the Curtain Call making you fall over and breaking your leg."
Broadway Legend Joined: 12/5/04
http://en.wikipedia.org/wiki/Bantcho_Bantchevsky : Bantcho Banchevsky told his niece that he was going to commit suicide b/w acts at The Scottish Tragedy in '88, then did just exactly that.
In the movie (and the play, of course) of The Dresser, the entire curse-removal is played out by Sir and his dresser (Tom Courtney) when Sir inadverdantly quotes from it.
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