When a giant asteroid dubbed "Flora" threatens the Earth, a mission to destroy it is quickly launched, led by hard-ass commander Rankin (Robert Horton). The disaster is successfully averted; however, a small piece of space slime is unwittingly smuggled back to the space station Gamma 3, where it begins feeding off the station's power cables and grows into a tall green monster with deadly, electrified tentacles. Worse, the creature heals rapidly and regenerates any severed anatomy into a whole new creature... eventually building up a veritable army of nigh-unstoppable monsters. Now Rankin and the Gamma 3's crew must fight a seemingly hopeless battle as well as interpersonal tensions in an effort to keep the beasts from reaching Earth.
This film is notable for being the first movie ever riffed by Mystery Science Theater 3000, on the pilot episode for the original KTMA-era show. Sadly KTMA lost the rights to the film shortly after the episode was made, making it a Lost Episode (and, given Best Brains' attitude toward their KTMA-era work, it's likely to remain lost. Keep Circulating the Tapes!).
The Green Slime contains the following tropes:
- Colony Drop: The whole plot starts when the rogue planet "Flora" wanders into the Solar System and threatens to crash into Earth.
- Commander Contrarian: Cmdr. Elliott constantly makes decisions that end up endangering the station further just because he doesn't likes being told what to do by Rankin.
- Cyclops: the slime creatures
- Red Eye Take Warning: The only eye the Slime creatures have is red and they are very dangerous to human life.
- Energy Absorption: The slime creatures can seemingly feed off of any type of energy, including sunlight and even Frickin' Laser Beams. On the other hand, they burn up just fine.
- Healing Factor / From a Single Cell / Asteroids Monster: What makes the slime creatures so dangerous (besides the fact that they, you know, kill people), and the reason they must be kept away from Earth at all costs.
- Heroic Sacrifice: Elliott finally does one thing right by Taking the Bullet for Rankin when the two of them set Gamma-3 to burn up in re-entry.
- Idiot Ball: Lisa, the station's chief medical officer, breaks quarantine when the mission returns from Flora by running in to greet them in the landing bay.
- Impaled with Extreme Prejudice: Because Throwing Your Rifle Always Works.
- Love Triangle: Cmdr. Elliott and Lisa are engaged; but Lisa was previously in a relationship with Cmdr. Rankin as well.
- The Medic: Lisa is the chief nurse in Gamma-3 and eventually the main doctor when Halverson's stupidity gets him killed.
- Monochrome Casting: Despite the space station supposedly having an international crew, everyone is Caucasian. Pretty odd for a film made in Japan, even if for American audiences.
- Noodle Incident: We never get too many details of the incident that rent Elliott's and Rankin's friendship. We do know that Elliott had mounted an attempt to save one life and ended up costing ten, and that Rankin duly reported this.
- Raygun Gothic: All over the place. The ships all look like a Retro Rocket and even if Gamma-3 is donut-shaped the Artificial Gravity is set so people are standing upright.
- Red Shirt: Michaels, Halvorson's assistant, is the first to go.
- Shock and Awe: The creatures' tentacles are so charged with energy, a mere touch is deadly.
- Suspiciously Specific Denial: When Rankin first arrives on the space station, the first thing Lisa tells Elliott is that she no longer has feelings for Rankin.
- Too Dumb to Live: Dr. Halvorsen runs into a part of the station which is currently overrun by slime creatures in an attempt to retrieve copies of his work. Needless to say, it doesn't end well for him.
- 20 Minutes into the Future