Invasion of Astro-Monster (1965)
— Japanese tagline
It went unobserved by the astronauts, but... The most gigantic monster explosion of the space age now being blasted into film
— International tagline
Godzilla and Rodan fight the monster from outer space to save the world!
— American tagline
Invasion of Astro-Monster (怪獣大戦争 is a Kaijū Daisensō, lit. Great Monster War)1965 tokusatsu kaiju film co-produced by Toho and UPA, and the sixth installment in the Godzilla series as well as the Showa series. The film was released to Japanese theaters on December 19, 1965.
The first Godzilla film to be a joint production between Toho and an American studio, Invasion of Astro-Monster picks up after the events of Ghidorah, the Three-Headed Monster. When astronauts Kazuo Fuji and Glenn visit the newly-discovered Planet X, they encounter the planet's intelligent inhabitants: the Xiliens. The Xiliens are constantly under attack by King Ghidorah, who they know as "Monster Zero." The Controller of Planet X asks to "borrow" Godzilla and Rodan in the hope they can once again repel King Ghidorah. The people of Earth comply, but not all is as it seems when the Xiliens issue an ultimatum demanding Earth's surrender and threatening to unleash all three monsters on Earth under their mind control. Glenn and Fuji find themselves in a race against time to find a way to sever the Xiliens' control over the monsters before the Earth falls to the invaders from Planet X.
In the year 196X, the World Space Agency (WSA) has sent astronauts Glenn and Kazuo Fuji to investigate the newly-discovered Planet X located just beyond Jupiter. Back on Earth, Fuji's younger sister Haruno has become romantically involved with inventor Tetsuo Torii, who has just sold his invention, the Lady Guard alarm, to a toy company represented by a woman named Namikawa. Both hope that this successful sale will make Fuji warm up to Tetsuo, as he objects to his sister's relationship with him. Glenn and Fuji's spaceship, the P-1, finally arrives on Planet X. Fuji tells Glenn to stay with the ship while he plants the American and Japanese flags on a nearby hill. A violent lightning storm passes overhead, after which Fuji locates a set of footprints which are unmistakably human. He returns to the landing site but the P-1 and Glenn are nowhere to be found. A tubular elevator ascends to the surface, from which a voice emanates telling Fuji to enter the elevator quickly. Fuji asks who is speaking, and the voice says it is one of what Fuji would call "Xiliens." Fuji draws his gun, but a laser mounted on the elevator blasts it out of his hand. Fuji finally complies and enters the elevator. He is transported to an underground complex, and follows the light to a dark room where Glenn is seated. The two reunite, after which the room lights up and several men dressed in black bodysuits with black visors over their eyes enter. One of these Xiliens sits across from the two men and introduces himself as the Controller of Planet X. He tells the men they have urgent business to discuss, but is informed over a monitor that "Monster Zero" is attacking. The astronauts ask what Monster Zero is, to which the Controller replies that it is a horrible space monster which terrorizes their planet. He brings up a video feed showing the space monster, which the astronauts recognize as none other than King Ghidorah. The Controller states that Earthlings give names to all things, while the Xiliens give them numbers. The Controller is informed that a hydrogen oxide plant was damaged in Monster Zero's attack, and quickly turns off the universal translator before leaving the room and shutting off the lights. Fuji and Glenn find themselves trapped within a forcefield and unable to stand up. The Controller soon returns and apologizes. The astronauts ask if hydrogen oxide is water, to which the Controller replies that water is more precious than gold on Planet X. He then states his reason for bringing the men here. He is aware that Monster Zero attacked Earth before, but was driven off by the combined efforts of Monster Zero-One and Monster Zero-Two: Godzilla and Rodan. He asks that the Xiliens be allowed to "borrow" the monsters; in exchange they will provide humanity with the cure for cancer. They respond that they don't know where the monsters are, but the Controller responds by giving the exact locations of both monsters. He asks Glenn and Fuji to talk to their leaders and sends them on their way in the P-1.
The people of Earth are largely welcoming to the Xiliens' proposal, but Glenn and Fuji are uneasy about the Xiliens' true intentions. They meet Haruno and Tetsuo at a restaiurant, where Fuji again voices his disapproval of Tetsuo. Tetsuo protests that he sold his invention, but admits he hasn't been paid yet. Glenn gives Tetsuo some words of encouragement before leaving for a date. Fuji reaffirms his disapproval of his sister's relationship before leaving as well. Tetsuo looks out the window and sees Glenn leaving with his date, who happens to be Namikawa. He visits the World Education Corporation office to ask about his payment, but is turned away. Later, Glenn takes Fuji on a drive out by Lake Myojin. He tells him that he was staying in a lodge with Namikawa last night and swore he saw the Controller walk into the room and say "All preparations are complete." Namikawa supposedly did not see the Controller and only complained that Glenn was groaning all night. The two see the JSDF surrounding the lake and make their way there. The head of the platoon explains that there is activity in the lake. This is confirmed when the water begins to rise suddenly. Glenn at first assumes this to be Godzilla, but it is revealed to be an Xilien UFO, confirming the two men's suspicion that the Xiliens were already operating on Earth. By daybreak, the UFO has been joined by two others. One UFO finally lands on the beach before a crowd of spectators. From it emerges the Controller, who holds a meeting with several Earth officials, including Glenn, Fuji, and their superior from the WSA, Dr. Sakurai. The Controller thanks the humans for attending and apologizes for operating on Earth without their knowledge, but reiterates the urgency of their situation. The other UFOs seek out Godzilla and Rodan's locations and begin to levitate the sleeping monsters with a tractor beam. The Controller states that they will be able to transport the monsters all the way to Planet X like this, and requests that Glenn, Fuji, and Sakurai accompany them to oversee the operation. Before leaving, Glenn kisses Namikawa farewell, but she asks him not to go and stay with her. He promises he will be back and leaves aboard one of the UFOs. Tetsuo sees Namikawa drive off and decides to tail her. He arrives on an island and finds a lone house there. As he approaches the door, a trap door opens underneath him.
Aboard the UFO, Sakurai asks to see the control room, but the Controller responds that the ship is controlled from the very chamber in which they are seated. His brain waves, he explains, are fed into the computer which controls the ship. The Controller then says that they are traveling at one-tenth the speed of light, and that they hope one day to reach the speed of light. Once they arrive on Planet X, the two monsters are deposited on the surface while the others watch from the underground complex. A giant ray gun fires a beam at the two monsters which dissolves the tractor field around them. Godzilla and Rodan both awaken and are immediately attacked by King Ghidorah, who flies overhead and blasts them with his gravity beams. Godzilla and Rodan immediately join forces and fight back, with Godzilla tackling Ghidorah to the ground and forcing the space monster to retreat. The Controller happily remarks that for the first time they have beaten Monster Zero, but turns to see Glenn and Fuji are both gone. The two astronauts wander through the Xiliens' complex, but find themselves pursued. They jump on an elevator which takes them to a grotto on the surface. There they find plentiful deposits of gold, demonstrating the truth behind the Controller's statement that water is more precious than gold. Glenn sees a female Xilien who looks identical to Namikawa and approaches her. When she does not recognize him and backs away, Glenn is confused until he sees another identical female Xilien approach. The men are then surrounded by several armed Xiliens and taken back to the Controller. He asks why the men wandered off without permission, and they respond that they wanted to see more of the planet. He asks what they learned, and Fuji replies that water is more precious than gold. The Controller retorts that while that is the case, they can easily obtain water and are not in a drought. Glenn asks why all the women have the same face, and the Controller rhetorically asks if Glenn admires a beautiful face. Glenn responds that beauty is individual, but the Controller cuts him off and says he will not debate him. He tells both men that normally their law would punish them, but they will be allowed diplomatic immunity as guests. With Monster Zero fended off, the Controller presents the men with a tape he says contains the cure for cancer, then sends them back to Earth in a superior replica of the P-1 the Xiliens constructed based on data they obtained from the original. As the spaceship takes off, Glenn and Fuji see Godzilla and Rodan watching them from the surface. They ponder if perhaps it is wrong to leave the two behind before they depart.
Fuji, Glenn, and Sakurai return triumphantly to Earth and insert the tape into a player before an assembly. The tape takes some time to start playing, but when it does it is revealed as an ultimatum from the Controller demanding that the Earth surrender and become a colony of Planet X. Glenn and Fuji are not surprised by this revelation but are nonetheless very concerned. The Controller goes on to say that they now control both Godzilla and Rodan as well as King Ghidorah, and will unleash all three to destroy Earth's civilization if their demands are not met. The world erupts into chaos as humanity debates whether to comply or fight back against the overwhelming power of the Xiliens. Glenn meanwhile heads to the World Education Corporation office to confront Namikawa, who is wearing Xilien attire. He asks if their relationship was all part of her plan, but she responds that she was initially only supposed to observe Glenn but genuinely fell in love with him. She begs him to return to Planet X with her where they can be married, but Glenn responds that he won't stop fighting back against the Xiliens. Namikawa insists it is too late, but Glenn angrily responds that it isn't. He looks and sees several armed Xiliens now in the room, who hold Namikawa back. She breaks free and runs to Glenn, slipping a note into his pocket before the lead Xilien vaporizes her with his gun. Glenn is enraged at Namikawa's death, but the Xilien responds that any who disobey the computer's orders must be eliminated. Glenn is taken to a cell where he encounters Tetsuo. Glenn fruitlessly searches for an escape before finding the note Namikawa left in his pocket. The note says that if Glenn is reading this that she will have been killed for disobeying the computer, but concludes with vital information: the Xiliens are vulnerable to a certain sound. Tetsuo immediately realizes this must be the sound produced by his Lady Guard alarm, which is why Namikawa's company bought it. He activates the device which causes the Xilien guards to run to the cell screaming in agony. They manage to pull the key off one guard and escape the cell, throwing the guards inside in their place. Glenn and Tetsuo escape the facility on the island and make their way to a boat on the dock. The leader of the Xiliens' Earth base asks the Controller for help, and his UFO opens fire on the boat and destroys it. Fortunately, Glenn and Tetsuo foresaw this and jumped off the boat, then swim the rest of the way back.
As the countdown to the Xiliens' invasion winds down, Fuji is working on a way to possibly cut off the Xiliens' electromagnetic waves and sever their control over Godzilla and Rodan. Glenn and Tetsuo soon arrive and inform the others about the Xiliens' weakness. A plan is put in place to play the Lady Guard's sound over the radio en masse while using newly constructed A-Cycle Light Ray Guns to free Godzilla and Rodan from the aliens' control. As this plan is set in motion, the Xiliens' computer begins recalculating, prompting the Controller to start the invasion early. Godzilla and Rodan begin to rampage through Japan, with the JSDF unable to halt them. The Lady Guard's sound is broadcast over the airwaves, with a request for anyone listening to turn their volume as high as possible. The A-Cycle Light Ray Gun trucks are dispatched and begin opening fire at the monsters. Weakened by the sound, the Xiliens are helpless to stop the humans' counterattack. The JSDF begins bombarding the Xiliens' Earth base, who ask the Controller to help them. The Controller refuses, saying that they will all escape to the unknown future before pressing a button that causes all of the UFOs and the Earth base to self-destruct. Their mind control broken, Godzilla, Rodan, and King Ghidorah collapse to the ground. Godzilla awakens first and wakes up Rodan, then resumes their battle with King Ghidorah. Godzilla punches Ghidorah's heads rapidly while avoiding his gravity beams. Rodan grabs Godzilla and flies directly into King Ghidorah, causing all three kaiju to topple over a cliff and into the water below. After a few moments, King Ghidorah surfaces and promptly flies back into outer space. Haruno asks Tetsuo if Godzilla and Rodan have died, but he responds that he doesn't think so. Glenn and Fuji congratulate each other and are happy the ordeal is over, but Sakurai informs them that they will be undertaking a diplomatic mission to Planet X, much to their frustration.
- Main article: Invasion of Astro-Monster/Credits.
Staff role on the left, staff member's name on the right.
- Directed by Ishiro Honda
- Written by Shinichi Sekizawa
- Produced by Tomoyuki Tanaka, Henry G. Saperstein, Reuben Bercovitch
- Music by Akira Ifukube
- Cinematography by Hajime Koizumi
- Edited by Ryohei Fujii
- Production design by Takeo Kita, Akira Watanabe
- Assistant directing by Koji Kajita
- Special effects by Eiji Tsuburaya
- Assistant Director of Special Effects Teruyoshi Nakano
Actor's name on the left, character played on the right.
- Akira Takarada as Kazuo Fuji, astronaut
- Nick Adams as Glenn, astronaut
- Kumi Mizuno as Namikawa, Xilien agent
- Keiko Sawai as Haruno Fuji, Fuji's sister
- Jun Tazaki as Dr. Sakurai, World Space Agency
- Yoshio Tsuchiya as Controller of Planet X
- Akira Kubo as Tetsuo Torii, inventor
- Takamaru Sasaki as Government representative
- Fuyuki Murakami as Medical representative
- Yoshibumi Tajima as Mobile commander
- Kenzo Tabu as President of World Education Corporation, Xilien
- Noriko Sengoku as Woman at boarding house
- Somesho Matsumoto as Religious representative
- Gen Shimizu as Defense representative
- Toru Ibuki, Kazuo Suzuki as Xiliens at Earth base
- Yasuhisa Tsutsumi as Captain of the First Survey Corps
- Nadao Kirino as Captain of the Second Survey Corps
- Toki Shiozawa as Women's organization representative
- Mitsuo Tsuda, Takuzo Kumagai as JSDF members
- Koji Uno as World Education Corporation president's secretary, Xilien at Earth base
- Masaaki Tachibana as WSA member
- Yutaka Oka as Reporter
- Rinsaku Ogata as JSDF member
- Tadashi Okabe, Ryoji Shimizu, Hideki Furukawa as WSA staff
- Kamayuki Tsubono, Minoru Ito as Reporters
- Haruo Nakajima as Godzilla
- Masaki Shinohara as Rodan / spectator
- Shoichi Hirose as King Ghidorah
- Goro Naya as Voice of Glenn
- Saburo Iketani as Announcer (uncredited)
- Yoshio Katsube, Akira Wakamatsu as Men at World Education Corporation, Xiliens at Earth base (uncredited)
- Haruya Sakamoto as JSDF member (uncredited)
Weapons, vehicles, and races
- Main article: Invasion of Astro-Monster/Gallery.
- Main article: Invasion of Astro-Monster (Soundtrack).
- Great Monster War (literal Japanese title)
- Great Monster War: King Ghidorah vs. Godzilla (怪獣大戦争 キングギドラ対ゴジラ Kaijū Daisensō Kingu Gidora tai Gojira, Japanese re-release title)
- Godzilla Goes to Space! (ゴジラ宇宙へ行く！ Gojira Uchū e Iku!, Japanese 8mm title)
- Monster Zero (United States)
- Invasion of the Astros (United States military bases title)
- Invasion of the Astro-Monsters (aborted United States release title; United Kingdom)
- Godzilla vs. Monster Zero (initial United States home video title)
- Godzilla vs. the Three-Headed Dragon (Thailand)
- Invasion Planet "X" (Invasion Planete 'X'; France; French Belgium; Invasie Planeet X; Dutch Belgium)
- The Monsters Invade the Earth (Los monstruos invaden la tierra; Spain)
- Godzilla Against the Space Monster (Godzilla contra el monstre de l'espai; Spain (Catalonia))
- Monsters of the Galaxies (Monstruos de las galaxias; Mexico)
- Command from the Dark (Befehl aus dem Dunkel; Germany)
- Gidorra: Command from the Darkness (Gidorra: Befehl aus dem Dunkeln; German DVD title)
- Godzilla versus Monster Zero (German TV title)
- The Invasion of the Astro Monsters (La invasion de los Astro-Monstruos; Mexico; L'invasione degli Astro Mostri; Italy; A Invasão dos Astro-Monstros; Portugal)
- Year 2000: The Invasion of the Astro Monsters (Anno 2000: L'invasione degli Astro Mostri; Italy)
- The Space Monsters Are Attacking (Avaruushirviöt hyökkäävät; Finland)
- Monster Invasion (Inwazja potworow; Poland)
- Monsters Coming from Space (Uzaydan canavar geliyor; Turkey)
- Attack from the Unknown (Utok z neznama; Czechoslovakia)
- Invasion from Space (Invazija iz svemira; Yugoslavia)
- The War of the Monsters (A Guerra dos Monstros; Brazil)
- Invasion of the Astro-Monster (Madman DVD title)
- King Kong 2000 (Lebanon)
View all posters for the film here.
- Japan - December 19, 1965 [view poster]; March 17, 1971 (Toho Champion Festival) [view poster]
- United States - 1970 [view poster]
- Thailand - 1966; 1989 [view poster]
- France - January 25, 1967; 1970 [view poster]
- Germany - 1967 [view poster]
- Brazil - October 7, 1967 [view poster]
- Poland - 1968 [view poster]
- Spain - July 16, 1968 [view poster]
- Italy - 1970; 1977 [view poster]
- Mexico - 1970 [view poster]
- Finland - 1973
- Portugal - November 30, 1978 [view poster]
- Belgium [view poster]
- Colombia [view poster]
- Czechoslovakia (Czech Republic) [view poster]
- Turkey [view poster]
- Yugoslavia [view poster]
- Lebanon [view poster]
- Greece [view poster]
- Egypt [view poster]
Invasion of Astro-Monster was licensed to UPA Productions of America, who co-produced the film with Toho, for release in North America. English dubbing was recorded at Glen Glenn Sound in Hollywood by June of 1966. Ironically, since Nick Adams delivered his lines in English on the set, Glenn was the only character whose voice was not dubbed over, although Adams seems to have been involved in at least some ADR that location shooting and other production factors would have necessitated. There were several alterations made:
- Dialogue was dubbed to English, with several changes made to the script. No date is given in the opening expository text, whereas the Japanese version states the film is set in the fictional year 196X, or 197X in the Champion Festival release. Tetsuo Torii was renamed "Tetsui Teri," and Haruno Fuji was renamed "Haruni" Fuji. The Xiliens' fabricated "cure for cancer" ploy was changed to a "miracle drug" capable of curing all diseases.
- Altered: Some of Akira Ifukube's score was re-arranged. The opening title music was changed to a cue from later in the film, "The Electromagnetic Capsule." Music during the film's climax was heavily edited, with some sections of the original, jettisoned opening title piece re-integrated.
- Deleted: All instances of Xiliens speaking in the language of Planet X were deleted or removed from the soundtrack.
- Deleted: Instances of Japanese expository text, including newspaper headlines for the P-1's return to Earth and the discovery of Godzilla in Lake Myojin, a placard inside the World Education Corporation building, and Dr. Sakurai handling the plans for the A-Cycle Light Ray Gun.
- Altered: The location supers for Lake Myojin and Washigasawa were rendered in English accordingly.
- Deleted: Fuji gesturing in anger and uttering "Damn it!" when the concealed Xilien UFOs in Lake Myojin surface.
- Deleted: The JSDF commander played by Nadao Kirino ordering his personnel to retreat from Rodan's location as an Xilien UFO approaches.
- Deleted: Long-distance shot of Godzilla and Rodan's capsules being lifted into the upper atmosphere, followed by a shot of the Earth receding.
- Altered: Part of a shot following the above deletions is moved before a long shot of Godzilla and Rodan's capsules.
- Deleted: Part of a short scene aboard the Controller of Planet X's flagship. Fuji tells Glenn to "be on [his] guard," to which Glenn responds "Tell me about it, pal." This exchange is restored (with Fuji's line in Japanese) in Toho's uncut Invasion of the Astro-Monsters version of the film used in the UK and on The Criterion Collection and Janus Films' Criterion Channel streaming platform.
- Added: Footfall sound effects were added to Godzilla's victory jumps on Planet X.
- Deleted: Xilien guards conversing (not in their native language) after Fuji and Glenn evade them in an elevator.
- Altered: The superimposed headlines during the global civil unrest montage were rendered in English accordingly.
- Deleted: Fuji cursing as the Xiliens unveil their control over the monsters.
- Altered: Namikawa's letter to Glenn is replaced with an English insert. Part of a medium shot of Tetsuo and Glenn reading the letter is repeated, making the scene run slightly longer than its Japanese equivalent.
The American version runs 93 minutes, a minute and 20 seconds shorter than the Japanese version. In his book Japan's Favorite Mon-Star: An Unauthorized History of 'The Big G', Steve Ryfle commented, "The Americanization [...] is respectful to the original Japanese version."
Although UPA's English version was finished in 1966, the film didn't see wide release in the United States until the summer of 1970. Distributed by Maron Films, the film was titled Monster Zero and frequently played as a supporting feature to UPA's Americanization of The War of the Gargantuas. Prior to this, the film had entered limited distribution as Invasion of the Astros in March 1970, exclusively screened at military bases in the continental U.S. The film later entered 16mm rental distribution under this title through the 1980's.
In 1980, UPA rechristened the film Godzilla vs. Monster Zero for television and home video. The film was released under this title on home video in the U.S. over the ensuing two decades, including in a 1998 DVD release by Simitar. Classic Media released both the original Japanese version of the film and a reconstruction of the initial theatrical American version (Monster Zero) on DVD in the U.S. in 2007, as Invasion of Astro-Monster. Janus Films provided an uncut English-dubbed version of the film previously distributed on video in the United Kingdom titled Invasion of the Astro-Monsters to streaming platforms once it acquired the rights to the film in 2017, and used the same version for its Godzilla: The Showa-Era Films, 1954–1975 box set in 2019.
United Kingdom release
The international version of Invasion of Astro-Monster premiered on Channel 4 in July 1990. A letterboxed VHS release from Polygram followed in 1992, in a set with Ebirah, Horror of the Deep and Destroy All Monsters. 4 Front Video also released it on VHS in 1998. Sony released both the Japanese and international versions on Blu-ray in 2019 as part of the The Criterion Collection's Godzilla: The Showa-Era Films, 1954–1975 box set.
When Invasion of Astro-Monster was first released in Japan on December 19, 1965, it sold 3,780,000 tickets and grossed ¥210 million, making it the tenth highest-grossing Japanaese film of the year. On its March 17, 1971 re-issue during the Toho Champion Festival, it sold 1,350,000 tickets, adding up to a rough total of 5,130,000 attendees.
In G-FAN magazine's readers polls, Invasion of Astro-Monster's rating has mostly risen over time: 7.4 in 1996, 7.2 in 2001, 7.7 in 2007, and 8.0 in 2014. It ranked sixth among Godzilla films in the most recent poll, tied with Godzilla, Mothra and King Ghidorah: Giant Monsters All-Out Attack. Ishiro Honda: A Life in Film, from Godzilla to Kurosawa authors Steve Ryfle and Ed Godziszewski praised Shinichi Sekizawa's "fast-paced script" and the "charming artificiality" of the art direction, though they noted that "the aliens could simply attack, but first they concoct an elaborate ruse [...] because that's what bad guys do." Director Ishiro Honda recalled fan complaints about the stock footage employed at the end of the film, and assistant special effects director Teruyoshi Nakano stated that "the audience's opinion was divided" about Godzilla's shie dance.
Simitar DVD (1998)
- Region: N/A
- Discs: 1
- Audio: English (2.0 Mono and 5.1 Surround)
- Subtitles: None
- Special features: Optional 1.33:1 presentation (cropped), Simitar-produced trailers for the company's kaiju releases, art gallery, trivia game
- Notes: Out of print.
Toho DVD (2003)
- Region: 2
- Discs: 1
- Audio: Japanese (2.0 and 5.1)
- Subtitles: Japanese
- Special features: Audio commentary by Yoshio Tsuchiya, theatrical trailer, interactive storybook, 8mm version of the film (5 minutes)
Madman DVD (2005)
- Region: 4
- Discs: 1
- Audio: Japanese (Dolby Digital 2.0 Dual Mono and 5.1)
- Subtitles: English
- Special features: Poster gallery, Japanese trailer, Madman-made trailers
- Region: 1
- Discs: 1
- Audio: Japanese (2.0 Mono), English (2.0 Mono)
- Subtitles: English
- Special features: Audio commentary for Monster Zero by Stuart Galbraith IV, Tomoyuki Tanaka featurette (8 minutes), poster slideshow
- Notes: Read the details of the U.S. version's reconstruction here. Reissued in 2012, both releases are out of print.
- Region: A/1 or B/2
- Discs: 8
- Audio: Japanese, English
- Subtitles: English
- Special features: All bonus features on Criterion's Godzilla Blu-ray, 1990 Ishiro Honda interview by Yoshimitsu Banno, interview with director Alex Cox, interviews with actors Bin Furuya and Tsugutoshi Komada, 2011 interview with critic Tadao Sato, unused effects sequences from Toho releases including Destroy All Monsters, trailers, illustrated hardcover book with an essay by Steve Ryfle and liner notes on each film by Ed Godziszewski
- Notes: Uses a new English subtitle translation. Sony distributed a Region B/2 version of the set in the United Kingdom.
- This film marks the first appearance of an alien race in a Godzilla film, a trope that would persist in subsequent films. The alien race introduced in this film, the Xiliens, would become popular recurring villains in the franchise, appearing in video games such as Godzilla: Monster of Monsters! and the television series Godzilla Island, and even returning in the film Godzilla: Final Wars in 2004. The Exif aliens featured in the GODZILLA anime trilogy are also inspired by the Xiliens.
- Invasion of Astro-Monster is the first Godzilla film to use extensive stock footage during action scenes, recycling shots from Rodan, The Mysterians, and Mothra during the Xilien-directed rampages of Godzilla, Rodan, and King Ghidorah.
- An updated version of the "Frigate March" from the soundtrack for the original Godzilla film, which would become known as the "Monster Zero March," is heard multiple times in this film, including during the opening credits and the scene where the Xiliens' mind control is broken.
- Godzilla's victory dance from this film appears as an unlockable attack in the PlayStation 4 version of Natsume Atari and Bandai Namco's Godzilla video game that can be used by Godzilla, Godzilla 1964, and Burning Godzilla.
- The kiss between Miss Namikawa and Glenn in this film was the first and only onscreen kiss in a Toho Godzilla film until GODZILLA: City on the Edge of Battle in 2018.
- Invasion of Astro-Monster was the first Godzilla film Toho co-produced with an American studio, namely Henry G. Saperstein's United Productions of America (UPA). It was the second collaboration between Toho and UPA, following Frankenstein vs. Baragon, which was released earlier that same year.
- Two props from previous Toho tokusatsu films appear in the film: Tetsuo Torii has the JX-2 rocketship from Gorath in his apartment, and the Atomic Heat Ray Gun from Mothra is the device the Xiliens use to revive Godzilla and Rodan on Planet X.
- The props used for the A-Cycle Light Ray Guns were reused and slightly altered to serve as laser weapons in the third episode of the Tsuburaya Productions series Ultraman, "Science Patrol, Move Out!" They took part in a JSDF barrage against Neronga.
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