Like E.T. in reverse, this pleasantly mediocre CG animation tale lands an astronaut on a distant planet whose green, four-fingered, newt-ish inhabitants are living in an innocent, 1950s-style state of development. Fearing the brain-eating “humaniacs” they see at the movies, the Planet 51-ers naturally view spaceman Chuck (voiced by Dwayne “The Rock” Johnson) as a monster. Save for timid teen Lem (Justin Long), who saves Chuck from the mob. Mom, can I keep him? Handsome doofus Chuck is a chip off the Buzz Lightyear block, and Planet 51 lacks Pixar polish (particularly in its writing). Still, it’s not a bad knockoff. The alternate-reality, Cold War–era design is cute: towns are laid out like crop circles; women wear beehives neatly coiffed above their antennae; and saucer-shaped cars wobble inches from the pavement. Before the alien can be returned home, however, Lem must thwart a paranoid general (Gary Oldman) and win the girl next door (Jessica Biel), with Chuck as his preeningly unreliable life coach. Fortunately, many chases and pratfalls attend their journey. The biggest laughs come from a neighborhood dog, modeled on the beast in Alien, that pees acid, and from a loyal, robotic six-wheeled NASA rover strongly reminiscent of WALL-E. An awkward European-American co-production, Planet 51 mainly succeeds at reminding you of all the better movies that inspired it.