A visually inventive science-fiction story, Phase IV concerns a group of research scientists working in the Arizona desert who find themselves confronted by an army of super-intelligent mutant ants. 
- Won 1975's Grand Prix at the International Festival of Science Fiction Films in Trieste, Italy.
- Saul Bass is better known for his work as a graphic designer, he designed the opening credits for many legendary movies and designed logos for companies and organizations including AT&T, The Girl Scouts, United Way, Warner Communications, and United Airlines.
Prologue: Lacking the $30,000 they need to continue experimenting on Joel, the Mads sell his (Joel's) car to raise some short-term cash. Joel reveals that he had $30,000 hidden inside it. The Mads, furious, retaliate by sending him "the ANT movie!"
Segment Two: Joel & the Bots discuss the first thing they plan to do when they get back to Earth. (Crow: "I'm going to kill Sandy Frank." Servo: "Well, that's a given.") Joel wants to turn off his water, which he accidentally left running.
Segment Three: The crew of the SOL enjoy a game of "I Spy," which quickly and inexplicably degenerates into a performance of "Wipe Out." Since he's the only one with working arms, Joel takes the drum solo. Mercifully, movie sign intervenes.
- "They must have ordered the plans from Mother Earth News."
Mother Earth News is a do-it-yourself magazine with a strong environmentalist bent, founded in 1970.
- A theater clip from this episode was included on the MST3K Scrapbook tape.
- This episode reveals that Joel used to own a Dodge (most likely a Dart Swinger, since Joel says "Not the Slant-6 Swinger!", as Dodge cars back in the late 50's up to early 70's had the Slant-6 engine).
- This is the first episode that doesn't start with Joel or anyone on the SOL. Instead, the episode starts on Earth with the Mads, who then give Joel a call.
- This is also the first episode to mention the possibility of starting a Fan Club, with Joel inviting people to call in and let him know what people think about the idea. It is officially announced 3 episodes later.
- During this episode, a Pizza 'N' Pasta commercial featuring Trace Beaulieu and Josh Weinstein in character as the Mads was first aired.
|preceded by: --||MST3K on KTMA||followed by: Season 1|
|1988 - 1989|
|K00||The Green Slime||Not aired||K08||Gamera vs Guiron||1989-01-08||K16||City on Fire||1989-03-19|
|K01||Invaders from the Deep||1988-11-24||K09||Phase IV||1989-01-15||K17||Time of the Apes||1989-04-02|
|K02||Revenge of the Mysterons from Mars||1988-11-24||K10||Cosmic Princess||1989-01-22||K18||The Million Eyes of Sumuru||1989-05-07|
|K03||Star Force: Fugitive Alien II||1988-11-27||K11||Humanoid Woman||1989-01-29||K19||Hanger 18||1989-05-14|
|K04||Gamera vs Barugon||1988-12-04||K12||Fugitive Alien||1989-02-05||K20||The Last Chase||1989-05-21|
|K05||Gamera||1988-12-11||K13||SST- Death Flight||1989-02-19||K21||The "Legend of Dinosaurs"||1989-05-28|
|K06||Gamera vs Gaos||1988-12-18||K14||Mighty Jack||1989-03-05|
|K07||Gamera vs Zigra||1988-12-31||K15||Superdome||1989-03-12|