“Then, the funniest dumb mistake [in WALL-E]: The ship apparently has a system for generating gravity, because it does not rotate to provide a "down" for the passengers. The gravity generator is presumably located in the bottom of the ship.

So when the navigation goes awry and the ship tilts, the gravity generator still remains in exactly the same position, relative to the rest of the ship. There is simply no way that, from merely tilting the ship, it would cause people to slide along the deck and bunch up along one edge.”

-- Orson Scott Card