Happy Feet/WMG

The emperor penguins have been spared extinction only temporarily.
Happy Feet took its cues on penguin behavior, pre-Mumbles, from March Of The Penguins -- both the French and the English editions. But anyone who's seen March of the Penguins knows that there are good reasons for the old traditions.

Don't worry, this isn't a Shaggy Dog Story (of either kind). Mumbles's actions help the food supply, not just of emperor penguins, but of every non-human species that eats fish or the ingredients of "fun food." The whole ecosystem had suffered; the whole ecosystem will be repaired in part. It's just that the Law of Unintended Consequences is inescapable.

The film is a coming out story.
Unfortunately, Executive Meddling prevented the true ending from ever seeing the light of film projectors.
 * The true ending that got cut involved alien abduction and resources being drained from the Earth in a Combine like plot. That would have Unfortunate Implications for either gays or closets.

The film is a metaphor for mental disabilities.
Hey, Mumbles was dropped as an egg!

Since it is a Hollywood film, the metaphor is the usual Hollywood version, just on a grander scale. The mentally disabled, because of their disability, are pure in heart. And because they are pure in heart, they can do great things... yes, they can even save the world!
 * It could easily be read as a metaphor for Aspergers Syndrome. Mumbles seems to be wired differently from the other emperor penguins, and he excels at a skill that they find strange. His father is also 'a little bit weird' (autistic-spectrum disorders are believed to be partially hereditary). Eventually, he learns to bond with others by having their different skills work together.
 * Following on that statement, this statement made the most 'exact' sense to me (sabrinadiamond)... It also may be a metaphor for going out of the closet.
 * This troper, suffering from Asperger's himself, and tired of all the religious/anti-religious controversy about whether Mumble was an analogy to being gay or not, thinks that this explanation makes the most sense, especially considering that the penguins make a big deal about how he hatched, and how, after Mumble was taken to "Mrs. Astrakhan", Mumble's mom says "So he's a little different--I've always kinda liked different." I've been referred to (behind my back when people thought I couldn't hear) as "A little different."
 * It sure makes a lot more sense than the 'gay' theory. After all, Mumble isn't gay - he actively tells Gloria he'd like to have an egg with her sometime - and the Adelie Amigos, if a little wacky, aren't gay; you see them hitting on the ladies quite a few times, and Lovelace isn't gay either. Not only does Mumble demonstrate Autistic qualities, other people demonstrate the current reactions to the Autistic - his parents send him to a special teacher, only to find that while she certainly brings out his talent (she tells him to look deep inside himself) it's not the talent they had wanted. The regular penguins aren't all cruel, but at one point when Mumble is trying to sing, one shouts out "You're spoiling it for everybody!" Several penguins are rather patronising, not treating him like an adult. It's actually refreshing to see an Acceptance Aesop that isn't about homosexuals for once.

The sequel's aliens will be actual aliens

 * Jossed, there's none. The antagonists are skua.
 * It's more like the iceberg in the archetypal conflict of Penguin (instead of Human) versus Nature. The Skua showed up for one scene.
 * That's right; the Skua aren't really antagonists; for the most part they're just assholes.

Eric has problems with the cognitive distortion catastrophizing.
Given how he overreacts over everything (to a ridiculous extreme), that would explain a lot.

Erik is adopted.
Mumble looks like he never fully matures, which might mean he was sterile. Maybe Erik's birth parents died while he was still an egg, and Mumble and Gloria chose to raise him since they couldn't have a chick of their own.