Audio problem: During the Spoonful of Sugar song Mary stands in front of a mirror and sings along with her reflection. Her reflection sings "they find." but the mouth movements do not match. (00:33:30)
Audio problem: In the French, German and Spanish version, in the song Supercalifragilisticexpialidocious, before Mary Poppins says the word backward. While Mary and Bert sing in the dubbed version, in these three languages, you can hear the English version in the background. You can hear it louder in the French version.
Audio problem: After the credits, Bert makes a riddle about the cop and right after his accordion is heard, but he isn't playing it.
Audio problem: After Bert rescues the Fox from the dogs the Fox says "Tis an elegant merry go round horse." If you look closely you'll notice that the voice recording is slightly off-sync with the animation on the Fox's mouth.
Chosen answer: For a good explanation, go to The Straight Dope: http://www.straightdope.com/mailbag/msupercali.html. It will give you pretty much everything that is known about this odd word.
Richard Welty