How might a teenager protect himself from that dreaded fate described in legions of sci-fi movies -- the 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" 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."

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"), only to realize he's interrupting an alien barbecue. Astronaut Chuck Taylor (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 odd, antennaed E.T. 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 start-up Ilion is a good-looking movie, with a lush retro-futuristic design. It's just low on laughs. (An American "Shrek" alumnus scripted it.) The superior "Monsters vs. Aliens" covered some of the same ground, referencing earlier movies from "Alien" and "E.T." to "2001," "The Right Stuff" and, naturally, "Plan Nine From Outer Space." Some of those work. But spoofs, a couple of cute neo-dogs and lots of bouncy '50s pop on the soundtrack can't hide the fact that, whatever the magical code is to concocting a state-of-the-art computer-generated cartoon for kids these days, Ilion hasn't cracked it.