Incidentally I got to thinking about Barbara's "Prima Donna" listening to the Met last week. On the quiz someone was telling, for the truth, a story about the accidental substitution of a loaded gun in the last scene of "Tosca" - and hastening to say that the tenor survived, although apparently injured, because when the soprano went to "wake" Mario, instead of singing, she turned and asked "Is there a doctor in the house?" which got a big laugh until she repeated it with, "no, I mean it!"
Unfotunately they rang the chimes and the story ended abruptly. I suspect it belongs in the same category as the trampoline.