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 51ers naturally view spaceman Chuck (voiced by Dwayne “The Rock” Johnson) as a monster—except timid green 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, but Planet 51 lacks the Pixar polish (particularly in its writing)—still, it’s not a bad knockoff. The alternate-reality, Cold War–era design is cute: towns laid out like crop circles; women wearing beehives neatly coiffed above their antennae; and saucer-shaped cars wobbling inches from the pavement. Sounds picture-perfect, but before the alien can go home, Lem must thwart a paranoid general (Gary Oldman) and win the girl next door (Jessica Biel), which means that Chuck must act 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 the robotic six-wheeled NASA rover that’s strongly reminiscent of WALL-E. An awkward European-American co-production, Planet 51mainly succeeds at reminding you of all the better movies that inspired it.