In Season 3, Episode 4 in the television series Black Adder, Why is the name of the Scottish play never taken? What about the time when the Scottish play is to be performed?
The 'Scottish Play' nearly always refers to Shakespeare's Macbeth. For some reason there is a superstition about the play, and theatre people never refer to it by name for fear of bad luck, but only referer to it as 'the scottish play'.
You can read about the superstition on wikipedia.