Genie, on reflection, I agree that the "fat lady sings" quotation is way older than 1978, and anyway, would a sports commentator have conjured this phrase out of thin air? I think not.

My initial thought was that it was Sam Goldwyn, (apparently not) but I still believe that it was somebody in the movie business who was trying to explain opera.

Somebody will come up with the answer I am sure. Victor Borge sounded promising but apparently it wasn't him either.

Murray