Jon's paraphrasing of "It ain't over 'til the fat lady sings" in another thread brought to mind the Blood, Sweat & Tears concert, which I think is worth recounting, that I saw at the Metropolitan Opera House many years ago.
Their second encore was a mystifying song, set to Mozart's Eine Kleine Nacht Musik, about a naked man terrorizing bus drivers, its chorus being "Beware, beware, beware the naked man....", and it was, like... "Huh?"
After a while I became aware that an IMMENSE valkyrie was descending to the stage from "Valhalla", i.e. the rafters, and as she neared the stage she sang a final "Beware the naked man", and the music stopped dead, and the house lights came up instantly.
It was over; the fat lady had sung.
(My impression of the audience reaction was that the vast majority of the audience had absolutely no idea what they had just seen.)