I don't know how it is now but the assistant stage manager had to understudy several parts. You had to be ready to go on at any time if the actor couldn't make it to the play. I didn't think anything of it.
“I'm still friendly with Dean. He still calls me on the phone from time to time. John Dean was fired and later ended up spending some time in prison for his role in Watergate.”
“I think Michael Caine is a perfectly good actor but it's obvious he's not going to be in one of my films.”