...delivers a few pleasant surprises, including a smart story...
—Adam Markovitz Entertainment Weekly
Kids and grandparents will both enjoy this fish-out-of-galaxy lark...
—Leah Rozen People
Although not bowling me over, Planet 51 is a jolly and good-looking animated feature in glorious 2-D.
—Roger Ebert Chicago Sun-Times
...a perky though not terribly imaginative feature aimed primarily at youngsters.
—Kirk Honeycutt Hollywood Reporter
...a jellybean of a movie: bright, colorful, sugary, and with no real content.
—Tasha Robinson Onion AV Club
...follows a hilarious concept with weak execution and way too many references to better films.
—Dezhda Gaubert E!
Lacking the crackling energy of Meatballs, Planet 51 never soars to the boundless heights, and skies, its animation so fantastically illustrates.
—Adam Keleman Slant Magazine
When the computer-animated space adventure Planet 51 resorts to silly bathroom humor just 15 minutes after the opening credits, we know we're in for a sorry experience.
—Claudia Puig USA Today
While it's not as awful as last year's cosmic themed failures -- Space Chimps or Fly Me to the Moon -- Planet 51 is endemic of what's wrong with the computer generated genre.
—Bill Gibron filmcritic.com
...a lame-brained toon that even kids will recognize as an insipid goof on sci-fi conventions.
—Todd McCarthy Variety