The film opens with mad scientist Dr. Clayton Forrester, working from an underground laboratory, explaining the premise of the film (and associated TV series). Mike Nelson and the robots Crow T. Robot and Tom Servo, along with Gypsy, are aboard the Satellite of Love high in Earth's orbit, when Forrester forces them to watch the film This Island Earth to break their wills; as in the television show, Mike, Crow, and Tom riff the film as it plays.
The film-riffing scenes are book-ended and interspersed with short, unrelated sketches:
- In the introduction, Crow attempts to dig through the ship's hull to return to Earth.
- Crow and Tom dare Mike to drive the Satellite himself, but he ends up crashing into the Hubble Space Telescope.
- Tom reveals that he has an "interocitor" like that used in This Island Earth. The gang tries to use Tom's device to return to Earth, but they instead contact a Metalunan (the alien race from the film) who is unable to help them to figure out how to use it correctly but does accidentally repeatedly zap Tom's head with a laser beam.
- After This Island Earth finishes, Mike, Crow, and Tom are far from broken, and are having a party on the satellite. Forrester, furious at his failure, attempts to use his own interocitor to harm them, but only succeeds in transporting himself into the shower of the Metalunan previously seen.
- In the finale, the film breaks the fourth wall as the crew returns to the theater and riffs on MST3k: The Movie's ending credits.
- Michael J. Nelson as Mike Nelson
- Trace Beaulieu as Crow T. Robot / Dr. Clayton Forrester
- Kevin Murphy as Tom Servo
- Jim Mallon as Gypsy
- John Brady as Benkitnorf