If you don’t know … there’s an old acting susperstition which prohibits actors from saying the play title “Macbeth” in a theater — with allegedly dire consequences if they do.

In true ghostly fashion, the show tanked — and, Bailey says his chaperone told him he played a part its unfortunate end. He jokes he even thought he killed the beloved Royal Shakespeare Company as a result.

Obviously, it’s all just a silly superstition … and, Bailey’s career hasn’t suffered too much because of his mistake — since he’s receiving pretty much universal praise for his performance as Fiyero in “Wicked” and its sequel “Wicked: For Good.”