In more relation to Macbeth and Harry Potter, Johan left me a rather interesting comment.

"Oh another thing where Macbeth has ties to the dark lord. You know how superstitious theatre people (like myself) is afraid of saying the name Macbeth out loud, and instead refers to it like the Scottish Play. Well that is very similar to people being afraid of saying Voldemort and referring to him with other names instead."

Further intrigued I decided to do some further research on this topic. It is completely fascinating. Regarding the curse, two sources quote:

"The curse attached to this play is, beyond doubt, the most widely observed and best-documented theater superstition in the English-speaking world."

"The history of the Scottish play doesn't merely include property damage, of course; you read of careers ruined, theaters burned down, and even deaths among cast, crew and families."

Macbeth is considered to be an unlucky play. In order to help counteract this curse a few rituals have been developed including.

• Not using the names of the Characters of the play, instead referring to the play as "The Scottish Play," "That Play" or "The unmentionable." Macbeth's death is often referred to as "the death" and Lady Macbeth is often just referred to as "The Queen"
• Actors do not ever quote the lines off stage.
• Actors often refuse to use props that have previously been used in productions of Macbeth.

Breaking these rules can result in disastrous consequences, so actors have a ritual to follow if these rules are broken to stop the chain of events beginning:

• Leave the dressing room, turn around three times
• Spit
• Knock on the door three times
• Beg to be re-admitted.

Alternatively the offender can quote other Shakespeare plays, commonly "Fair thoughts and happy hours attend on you!" (Merchent of Venice) or "Angels and ministers of grace defend us," (Hamlet) and "If we shadows have offended," (Midsummer Night's Dream).

Throughout the history there has been "Evidence of the Curse" this was really interesting, but I can't type them all here. The most interesting was the one where the actor who played Macbeth held a grudge against the actor who played Duncan and replaced the prop daggers with fake ones, thus killing him live on stage. You can find more stories here and here.