Worlds collide in more ways than one in the intergalactic “Planet 51.” An animated alien science fiction comedy featuring Cold War social commentary and impressive CGI graphics, the film inverts the traditional “aliens attack Earth” storyline by portraying a human invasion of an alien society. Despite a political allegory that is too subtle for children yet too obvious for adults, the film succeeds as an entertainingly cute, if not totally memorable, space comedy.

The alien community of “Planet 51”—brought to life by co-directors Jorge Blanco, Javier Abad, and Marcos Martinez alongside screenwriter Joe Stillman (“Shrek”)—immediately calls to mind an idealized 1950s America. White picket fences and pink-lipsticked Stepford alien wives make up the charming atmosphere of their small-town utopia. The film acquires all the makings of a sci-fi romantic comedy when Lem, the teenage protagonist voiced by Justin Long (of Mac commercial and “He’s Just Not That Into You” fame), reveals his crush on Neera (Jessica Biel). But their budding romance is complicated when American astronaut Chuck Baker (voiced by Dwayne “The Rock” Johnson) lands on Planet 51 and is shocked to discover the thriving alien civilization. The Planet 51 community—extremely fearful of a hostile takeover by an “alien” race—persecutes Chuck, who solicits help from Lem in a quest to return to his home planet.

The blatant parallel with Cold War-era McCarthyism—which manifests itself through the growing paranoia of the aliens as they search for Chuck and accuse their fellow townspeople of being his zombie followers—is clever and original in a movie made for children. But most of the references will be lost on the film’s younger audiences, and reminders of the film’s political subtext—the aliens’ collection of UFO artifacts includes none other than the Sputnik satellite, complete with “USSR” imprinted in Russian—are frequent enough to be irritating to adult viewers.

The rest of the all-star cast funnels their respective talents into the standard roster of kid-movie roles. Sean William Scott (“Role Models”) takes on the wisecracking sidekick, while the inimitable John Cleese is the requisite Evil Professor, whose refined British accent seems wholly out of place in the apparently country-less Planet 51. As the unexpected visitor, Chuck is self-centered and arrogant, and he struggles to understand why the celebrity status he enjoyed at home carries no weight in his new surroundings. As he’s pursued by an army led by the blandly malevolent General Grawl (Gary Oldman), Chuck finds himself forced—albeit predictably—to come to terms with his excessive narcissism. In a similar realization, Lem neatly delivers a moral lesson to his fellow townspeople regarding the danger of blindly fearing the unknown.

Despite this fairly straightforward unfolding of events, the film remains entertaining. Amid the obligatory smattering of slapstick comedy scenes, whimsically amusing details highlight the differences between Earth and Planet 51. The aliens exchange “high fours,” alien children don astronaut costumes for the premiere of a new “Humaniacs” movie, and Chuck’s “Macarena”-playing iPod is labeled a dangerous and cruel weapon. Chuck’s mechanized companion, Rover, is a source of endearing robot humor that resonates with all audiences, despite being shamelessly borrowed from “WALL-E.” Although veering on occasion towards crudity (“That’s an odd place for his antenna,” says one character after glimpsing Chuck in the nude), the movie’s humor keeps the film from becoming mired in political commentary.

“Planet 51” features several references to well-known space movies, notably “Alien” and “E.T.: The Extra-Terrestrial.” The dog-like alien pet belonging to Lem’s family recalls the eyeless, orb-like forehead of Sigourney Weaver’s original foe, while Elliott’s iconic bicycle silhouetted against the moon in “E.T.” is briefly parodied. By alluding to well-known scenes from past films, these references are perhaps a tongue-in-cheek acknowledgement of some of the less original aspects of “Planet 51.” Though the political subtext fails to truly resonate with either audience, the film’s visual appeal and effective humor provide something for everyone.