No... it's not over "until the fat man sings"...
OK--- apologies if I offended anyone with the "body weight" reference...
"It's not over until the fat lady sings" is an old term that goes back to the Opera Era of Wagner....
https://en.wikipedia.org/wiki/It_ain%27t_over_till_the_fat_lady_singsHell--- I seem to recall some sort of similar reference in the classic Alfred Hitchcock Film: "The 39 Steps" from way back in 1935.... (Still could be the memory cheats and it has been at least a couple decades since I last watched the movie).