'Planet 51': High on sci-fi, low on laughs

How might a kid — OK, a teenager — protect himself from that dreaded fate described in legions of sci-fi movies (including "The Fourth Kind"), the anal probe? If you weren't thinking "Champagne cork," you were way off, according to the sci-fi kids cartoon "Planet 51."

A genial but generic riff on sci-fi movie history, "Planet 51" has barely enough slapstick to keep the kids interested. Children won't get the many sci-fi movie references — or the cork gag — and adults probably won't find them that funny.

But there's an adorable Mars Rover-like robot named "Rover" who wags his antenna and chases rocks like a Jack Russell, and an alien Chihuahua shaped like the beast from "Alien." He scooches his butt across lawns and carpets just like a real Chihuahua. But don't ask what happens when he pees.

The big joke here — given away in the movie's trailers — is that an alien has "invaded" a provincial and paranoid suburban town. And the alien is us, a NASA astronaut who touches down, bounces out with his American flag (humming "Thus Spake Zarathustra" from "2001: A Space Odyssey"), only to realize he's interrupting an alien barbecue. Astronaut Chuck Baker (voiced by Dwayne Johnson) has discovered an alternate alien 1950s — with drive-ins, doo-wop music, "duck and cover" drills and VW hover-Beetles.

His first thought — "Kennedy's gonna freak" when Mission Control hears about "sea monkeys dancin' to the oldies." But the "sea monkeys," conditioned by years of "It Came from Outer Space" horror movies, are the ones who freak.

Lem (Justin Long) is the E.T. that Chuck talks into helping him get back home, evade the trigger-happy Army general (Gary Oldman) and the jumpy natives who are sure that the guy in the puffy suit wants to eat their brains.

This first offering from Spanish animation startup Ilion (working for Sony-Tristar) is a good-looking movie, with a lush retro-futuristic design, a few spoofs that work and lots of bouncy '50s pop music. It's just low on laughs.