Most critics give Planet 51 a mixed but good-natured notice: an amiable children’s animation that raises laughs without leaving much behind. The praise clusters on the humour. Several reviews enjoy the broad slapstick and the steady run of in-jokes for film fans, and the setting’s playful resemblance to 1950s small-town America is generally found a pleasing idea. Empire is the one outright admirer, calling it fun and charming for all its lack of big-studio polish.
The reservations cluster on originality. Most reviews note that the science-fiction references are recycled rather than reworked, and that the story and characters are too thin to carry a feature; The Guardian also complains the comedy runs out before the end. The spread is wide. Variety is the harshest, finding the film lame-brained and incurious about its own world, while most others settle for a shrug: pleasant enough for small children, not ambitious enough for anyone else.
