Scientifically advanced wanderers from the destroyed planet Mysteroid request a patch of land on Earth and the right to marry earthling women. After a demonstration of their destructive abilities from the help of their giant robot Moguera, mankind must decide whether to capitulate or to resist. Predictably, the earthlings choose to resist. The Mysterians have giant burrowing dome/bases that can come up out of the earth and deploy death rays that emanate from the dome's crown and can melt tanks and jeeps as if they were plastic.
Miraculously, the earthlings develop their own death-ray equipped, agile rocket-aircraft, which enable them to blow up the domes.
- Kenji Sahara - Jōji Atsumi
- Yumi Shirakawa - Etsuko Shiraishi
- Momoko Kōchi - Hiroko Iwamoto
- Akihiko Hirata - Ryōichi Shiraishi
- Takashi Shimura - Dr. kenjirō Adachi
- Susumu Fujita - General Morita
- Hisaya Itō - Captain Seki
- Yoshio Kosugi - Commander Sugimoto
- Fuyuki Murakami - Dr. Nobu Kawanami
- Tetsu Nakamura - Dr. Kōda
- Yoshio Tsuchiya - Mysterian Leader
A November 1, 1957 report states that Southeast Asian distribution rights to The Mysterians were sold to Shaw & Sons of Hong Kong for the highest amount paid for a Japanese film to that time. Rights to other parts of the world were sold for a record price for a Japanese film to Topaz Film Corp. in February of 1958.
Lobby card for the 1959 US release of The Mysterians film were released to the U.S. in May of 1959. In July, The New York Times called the film, "an ear-splitting Japanese-made fantasy, photographed in runny color and dubbed English," and concluded with, "This Metro release is crammed with routine footage of death rays and scrambling civilians, not one of whom can act. Tomoyuki Tanaka produced the mess and Inoshiro Honda directed it. Peter Riethof and Carlos Montalban are responsible for the 'English version,' and may it spread no further linguistically."
- In Godzilla vs. SpaceGodzilla, special effects director Koichi Kawakita redesigned the giant robot Moguera into an anti-Godzilla mecha for the later film, called "M.O.G.U.E.R.A." (Mobile Operation Godzilla Universal Expert Robot Aerotype).
- Ryuhei Kitamura's Godzilla: Final Wars features an anti-monster defense organization called the Earth Defense Force.
- Moguera's inclusion was a last minute idea as producer Tomoyuki Tanaka felt the film needed a monster.
- Moguera was originally conceptualized as a living breathing monster, however director Ishiro Honda reworked it into being a robot as a way to further demonstrate the technological power the Mysterians possessed.
- Moguera's original concept can still be seen in story board stills, which depicted him as a half mole half reptilian monster. Though the design was never used, some key details were later used in the monster Baragon for the film Frankenstein vs. Baragon. Most notably was the monsters burrowing ability, heat ray, and a ridged back.