First animated film by Australian director George Miller - kind of a strong mix between Disney's first couple of films, like Bambi and Fantasia, and Martin Rosen's Watership Down. A classic fable with no shortage of mythic and political undertones. With dancing penguins, to boot.
Because of this, when it was initially released, more than a few people including several notable critics dismissed it because it was "too dark and pretentious for a children's film;" right now, it's right in the middle of one of those common critical reevaluations of certain films that come around every so often, and there doesn't seem to be an end to the praise it's getting for, among other things, introducing several new techniques and ideas into CG animated filmmaking that have since been reused by Pixar, and for its sense of filmmaking literacy.
When I first saw Happy Feet, I thought it was some whack movie about dancing penguins. And, then I saw it again. /i