I spent many years in the theatre business. Here are some superstitions that I remember…
Never whistle in the box office. It’s bad luck. I have actually been chased out of a box office for whistling by the Ticket Manager.
When the Stage Manager calls “places” or lets the actors in the dressing room know that they have “X-minutes to places,” everyone answers, “Thank you.” It is considered to be bad luck to do otherwise. The reason for responding is that the Stage Manager needs to know that all actors are in “place” (i.e., in the dressing room regardless of whether they are going on stage immediately or not). If they do not respond, it means that they are not in the dressing room - which could mean trouble for show and a substitute will have to be found. In modern theatre, the Stage Manager seldom if ever enters the dressing room to call “places” - it’s now generally done on an intercom. Nonetheless, the actors will still call out “Thank You” even if it the message comes over the intercom. It is considered to be less than professional (bad luck) to do otherwise.
There are a number of so-called “bad luck plays” besides Macbeth in the history of theatre. I remember doing a play by Carlo Goldoni (I believe it was “Servant of Two Masters” which was considered to be a bad luck play - mainly because several of the lead actors had died or were injured shortly after the original performance back in the 1700’s). This, I was told by the director of our performance (I was interviewing him for our PR effort before the play was staged), that this was something which must “never be spoken - it will bring bad luck!” It is my understanding that there are many of such plays and operas.
Never give flowers to a performer before the performance. It’s bad luck. If you must give flowers, wait until the curtain call.
Never turn off the “Ghost Light” on stage. Every theatre has a single bulb lamp illuminating the stage which is to remain on at all times. I suspect that in the pre-electric days, that lamp would’ve used gas which could be highly volatile. Don’t mess with the lamp (i.e., don’t burn down the house).
On the subject of lighting, it is a fact that in a Union house (IATSE), the House Management is only allowed to touch certain specific light switches, and the IA folks will cause havoc if the House activates any lights that are under their purview. Turning on the wrong lights by the wrong people could end up becoming a labor dispute.
There’s lots of other stuff like this, but this is all I can remember for now. I’ll come back with some more if they come back to me.
Break a leg!