It aint over 'til the Fat Lady Sings

Have you ever heard that colloquialism before? I remember hearing it growing up and I've used it a few times myself.  However I guess the phrase just hasn't been used that frequently as of late.  

Please, allow me to back up a bit and take you with me to our Sunday afternoon.  We, the Reynolds clan, were all sitting, eating popcorn, and watching the Phillies and Giants play baseball.  The Giants were just looking pitiful to put it plainly.  I mean really, they didn't seem to have any tricks up their sleeves and the pitchers were just off, not to mention their bats.  On the opposite side of the fence you had the Phillies. In our home, Jackie is the lone supporter of the Phillies and she was thrilled to see the Giants off and the Phillies dominating the scoreboard. Most of us had given up on the Giants, except for Jake, who declared, "It aint over 'til the Fat Lady Sings."  The kids looked a bit startled and wondered who is this fat lady, will she really sing?? Well, we don't know.  Jackie had a grand look of intrigue sweep across her face.  She disappeared and to be honest none of us noticed nor cared.. We were too wrapped up in the game.  Approximately 7 minutes after Jackie had disappeared, she reappeared laughing, and moaning some awkward soprano tune..  When we looked up, this is what we saw:

Yes, she had stuffed her clothes and was singing and saying, "Daddy, you said it aint over 'til the fat lady sings, well she's singing."  We laughed and it was really hysterical, because she's so witty.  This girl is a riot!  I know only a couple of other people who could pull something like this off without prompting.  I won't name them though.. Any guesses?

You may guess away, but I won't divulge my knowledge on the matter.