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Very charming! A not the smoothest motions in the world, but the animation made me smile never the less. : )
All I can point out is watching whats on top of what, like when the balloon started to somersault, a few buildings started overlapping each other the wrong way. Perhaps some subtitles for the parts when just the mouths are moving as well, or actions from the characters if you didn't really have anything planned out for dialogue.
I hope your friend liked her present!