I can't tell you why she started singing it, I'll only say -- think of your job on one of its worse days!!! My favorite is the one featuring Charlie Sheen, come on, he had good moments! Enjoy.
Ry Cooder and Bobby King
From the movie Cadence:
Sam Cooke, the original
Growl and roar-it's okay to let the beast out.-© J. Hali Steele