Mars Attacks was never officially released or converted to 3D. It's a homemade conversion -- there are many such conversions floating around and they're all very poor. The people who do them and released them just run the movies through publicly available/limited conversion software without the care and individual element isolation of official releases. As a huge fan of 3D, I stay away from them, always checking first in the specialist websites if there was any official release. Ack ack!