In the original version, the ending was different. Mike and the 'bots made an elaborate practical joke in which they used the interociter to transmogrify a regular ant into a MutAnt (affectionately known as Scrotor), who promptly throttles Dr. Forrester. Meanwhile, Crow uses the chainsaw he found in Tom Servo's room to once again try to "dig" his way back to Earth. This was the version shipped to some film critics before the studio demanded they re-shoot the ending (too "scary".) It was finally shown to a public audience at the second MST3K convention, along with another deleted scene involving air being sucked in space a la Apollo 13.
Also cut was another host segment in which, during a meteor shower, the robots and Mike go back to the storm shelter (Crow tried to tunnel through space with it at the beginning), and when the air is cut off, the 'Bots run around heroically (and hysterically) to save Mike from asphyxiation.