On a planet far far away, a green Martian species exist quite quietly, content to keep their sights set on their own world and nothing more. The population of this world (I guess it's called Planet 51 but I'm not really sure) is going through their version of the 1950s, complete with poodle skirts. Everything is fine until human astronaut Captain Charles Barker (The Rock) lands on Planet 51, unaware of its inhabitants. Things take off from there as must of the Martians organize a manhunt to track down Barker while Lem (Justin Long) attempts to help the alien get back to his shuttle.
The first 15 minutes or so of "51" aren't bad. It's kind of a fun "Back to the Future"/"Pleasantville" mix that comes off as a bit inventive if uninspired. And you could do worse in the voice talent category than Justin Long. Where this movie made a decisive turn for the worse was the minute, nay, the second that The Rock's Captain Barker stepped onto the screen. Some actors have the ability to move from live action to animated feature seamlessly and some don't. It's a different talent, a different skill set that some great actors can't master. Of course, this transition is probably a little easier for an actor who can, in fact, act. Unfortunately The Rock is not an actor and he seems hell bent on proving his talent deficiency at every opportunity. I have yet to see The Rock do anything in his short career that hasn't made me want to set myself on fire. And I refuse to call him Dwayne Johnson until he does something to prove he's an actor, not a wrestler masquerading as an actor. In all seriousness, his arrival in "Planet 51" is the exact moment that the movie begins a steady decline. Very rarely have I seen a single actor or character suck the life out of a movie as quickly as The Rock did here. It's so sudden that you almost want to give the guy an award if only there was a sophisticated way to say, "You sucked so bad that the entire movie crashed around you the minute your character appeared." He's awful. In all fairness, the script, which is riddled with poor attempts at adult humor and outrageously bad dialogue, does him absolutely no favors. But it wouldn't have mattered if "Planet 51" had been penned by Tarantino, Nolan, Sorkin, or any of the others who stand out among the Hollywood elite. What would have been a decent enough kid's flick is instead left broken and mangled on the side of the road, another victim of what The Rock is cooking.