The sequel to the 2006 animated blockbuster, "Happy Feet Two" is a feel-good movie full of music and dance. It also contains a subtle but clear message about global warming and how it has affected the polar ecosystem, as it figures prominently in the plot: melting ice has stranded the penguin community, cutting them off from the ocean and their food supply.

"You can't tell the story about this world without it being about the impact, about the environment," says writer/director George Miller. "All these massive icebergs are breaking off, and they're tracked by satellite. They do block off the penguins. There is melting so the penguins are going south. There are big shifts in the krill population, the great biomasses that feed all the animals there. The species are getting more mixed up, and that's what we tried to indicate in the movie — it's there as part of the background narrative."

Miller was also committed to "follow nature and natural history as much as possible. All the creatures are designed pretty strictly to the anatomy of krill and elephant seals and penguins, and I think that gives the film a lot more authenticity," he believes. "But the guiding premise of the film is the notion that together, despite our differences, we can overcome the chaos of the world.

Reprising their roles from the first "Happy Feet" are Elijah Wood as Mumble, now a dad to dance-challenged Erik, and Robin Williams as Lovelace, who he describes as "a little bit of Foghorn Leghorn and Barry White" and Adelie penguin Ramon, "small but fierce, much like myself," this time given a love interest (Sofia Vergara). Also new to the flock are Pink, playing Mumble's mate Gloria and singing three songs, Matt Damon and Brad Pitt as Bill and Will the Krill, voiceover veteran Hank Azaria as a Swedish-accented puffin named Sven, and rapper-actor Common in his first animated movie role as a papa penguin, Seymour.

Miller had cast Common in a "Justice League" movie that fell apart, "but I called him up and said, 'You can't play the Green Lantern but how about playing a penguin?'" noted the director, who had his actors come to Australia and record together, which "made it more of a collective, immersive experience," says Wood. Azaria, who prefers to record solo on "The Simpsons" so he can focus, found that "being together really did make a tremendous difference. Not only did that free us up to improvise and bounce off each other a lot, but it became a very, rather intense character exploration. It was one of the most gratifying creative experiences I've ever had in any medium."

Common likens it to the creative process in the recording songs and albums. "It was really kind of like being in a freestyle session to a certain extent where you can improv and come up with great songs and riffs," praising the variety of the movie's music that ranges from rap to opera, "Under Pressure" to the theme from the TV western "Rawhide."

Miller, who had to put plans to make "Mad Max: Fury Road" on hold when "unprecedented rains" turned the Australian desert into "a flower garden" and salt flats into a lake "full of pelicans and fish," does plan to revisit that film "theoretically, next year." He isn't thinking about a third "Happy Feet," preferring to allow ideas to come forward organically if and when the time is right. "If something comes up that's really exciting and I can convey that enthusiasm to other people then there would be a third one," he says.

Meanwhile, Wood is keeping busy with projects including "The Hobbit," a new Syfy version of "Treasure Island," and season two of the FX series "Wilfred." Eco-minded at home, "Every time I leave the house I turn all the lights off, I recycle, and use products that are biodegradable," he says.

Photos: Warner Bros.

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