The show must go on...or must it?

The saying goes that "the show must go on" and generally it does. But there are always close calls. So, what's your OTP close call story where the show almost didn't go on? Perhaps, the lead lost his voice or the director was in an accident prior to opening. Ever been in a show where someone was thrown on stage last minute to cover? Let's hear your stories about the performances that almost didn't happen.