Hi Dorothy! **waves**
It may have been used on the soundtrack of "Rain Man", but it was actually introduced by the immortal Fred Astaire in "Top Hat" (1935).

As for your quote, surely this is from "My Fair Lady", wherein the staff comments that Eliza ought to retire, even though she "could have danced all night".

Now let's try a famous quote from the 1940s:
"Say, can you help a fellow American who's down on his luck?"
BONUS: this same film also contains the much-parodied quote: "Badges? We don't need no stinkin' badges!"
