This film was the last appearance of the monster Anguirus and only appearance of King Shisa until their long-awaited return 30 years later in Gojira: Fainaru uôzu (2004).
The only Japanese Godzilla movie that saw a release in Hungary. It had a short run in cinemas in 1989, but was met with unfavorable reception, with critics calling it an "utterly worthless film" and "one of the worst science fiction movies in history". It was so badly received that no other Japanese Godzilla film was released thereafter, neither theatrically, nor on home video or television. As a result, most people believed Roland Emmerich's American Godzilla (1998) to be the first and only "true" Godzilla film.
This was the first Godzilla film, in its original Japanese version, to finally give onscreen credit to the suitmation actors with the names of the respective monsters they played. (Up to that point, suitmation actors did receive onscreen credit, but just as regular cast members). All Toho-produced Godzilla films have since maintained this practice.
This was produced as Godzilla's 20th Anniversary film (which was also stated in the original Japanese theatrical trailers).
In the German release of the movie, MechaGodzilla is called King Kong. The reason for this name-change is unknown, although it is likely that the German distributors simply wanted to ride on King Kong's popularity. It is also possible that they have been inspired by the ape-like aliens who control the robot in the movie, or that "King Kong" was simply something of a catch-all term for giant monsters in general. Film historian David Kalat also suggests that the distributors have been confused by the film King Kong Escapes (1967), in which Kong fights a mechanical version of himself, and incorrectly thought that the name "King Kong" referred to the giant robot. It is also of note that another giant robot character, Jet Jaguar from the movie Gojira tai Megaro (1973), was also called King Kong in the German dubbing.
When Universal Studios, responsible for both the The Six Million Dollar Man (1974) and the The Bionic Woman (1976), threatened to sue Cinema Shares Releasing over the title (Godzilla Vs. the Bionic Monster), the movie was quickly re-titled Godzilla vs. the Cosmic Monster.
The guardian monster King Shisa is based on the actual "shîsâ" lion-dog guardian statues in Okinawa. Originally from China, they are statues that ward off evil spirits. Another Japanese name for them is "komainu" (lion-dog).
The metal in the bowl of Professor Miyajima (Akihiko Hirata)'s magnetic pipe is made of a fictional element called Astanopkaron ("Asutanopukaron" in Japanese), which was made up just for this film.
The cavern in which the Third Planet Aliens have their secret base is the Gyokusen Cave, a real cave in Okinawa, and also a tourist attraction.
This was Hiroshi Koizumi's final appearance in the classic Godzilla film series (the Showa Series). He would return in Gojira (1984), the first film in the VS Series (AKA: Heisei Series).
The ferry Shimizu (Masaaki Daimon) and Saeko (Reiko Tajima) travel in to get to Okinawa is called the Sunflower Sapporo, which is a real-life (and still active, as of 2013) ferry. The original owners, Nippon High-Speed Ferries (Nippon Kôsoku Fêrî), was one of this film's sponsors.
This is the last Godzilla film directed by Jun Fukuda.
The main objective of Teruyoshi Nakano, director of special effects, was to show that Godzilla movies could be as exciting and boisterous as the popular and more expensive American effects-films of the time, hence, all the focus on big and colorful explosions in the movie.
Mechagodzilla was inspired by Machanikong from King Kong Escapes (1967). Toho producer Tomoyuki Tanaka had trouble coming up with a new monster and recalled the popularity of the mechanical doppelganger of King Kong and insisted upon the creation of a mechanical Godzilla. This is ironic since Godzilla in part owed his own birth to King Kong (1933), which jump started the giant monster genre and inspired Eiji Tsuburaya to become a special effects director.
The concepts of Mechagodzilla and King Seesar were not in the original, first draft of this movie. The film was originally titled "Giant Monsters Converge on Okinawa! Showdown in Zanpamisaki" and would feature Mothra, Anguirus, and a new alien monster called Garugan. Toho had been pining to use Okinawa in a film since Tsuburaya Productions obtained permission from Toho to borrow Godzilla for a film to be called "Godzilla vs. Redmoon," which was never made. As for the Showdown in Zanpamisaki script, Mothra was eventually dropped in favor of a new character named King Barugan, which would eventually evolve into King Seesar. Garugan was then dropped in favor of the robotic Godzilla. King Seesar's origins as a guardian monster may also have roots in Okinawan mythology and the aborted "Godzilla Vs. The Space Monsters: The Earth Defense Command" script from the movie that eventually became War of the Monsters (1972). The original story-line for that film featured a giant statue, Maijin Tuol, which comes to life to aid Godzilla.
This is the final Godzilla film to feature a score from Masaru Sato. It was an all new score, which fitted exceptionally well with the film, and only has one stock music track that Sato re-uses from Kaijûtô no kessen: Gojira no musuko (1967) for the King Seesar vs Mechagodzilla fight.
The film was widely criticized for its supposed lack of substance. However, some critics pointed out the actual historical context behind the plot. There had long been tension between Japan and the island Okinawa, and Okinawa was the home of American military bases at the time that brought the threat of the Cold War to the island. With the aliens controlling Mechagodzilla representing the outside invading force, Godzilla representing Japan and the mythical King Caesar standing in for Okinawa, the film proposes cooperation between the two nations, standing together against a common adversary.
In France, the film was released in 1977, after its followup Mekagojira no gyakushu (1975), and was even falsely advertised as a sequel to that movie.