Corrected entry: All of the aliens are able to stand up normally, which gives the impression that the planet has gravity. But, the hamburgers that the alien flipped near the beginning of the movie, when Chuck first stepped out of the spaceship, give the impression that the planet has no gravity.
Phixius
11th May 2010
Correction: No, they don't. They give the impression that these aliens' grilling technology is light years ahead of our own.
Phixius ★