- Fan Nickname: Fans have commonly named Shosaku Takasugi as "Corn Guy" after his introductory scene where he accidentally makes the main character faint, believing he assumed his corn was a gun.
- Flip-Flop of God: See God Never Said That below:
- God Never Said That: For a long time it was shown on the movie's poster that Gigan could fire an Eye Beam from his forehead, above his eye, yet this ability was never shown in the film, though later appeared in Final Wars and the Atari/Pipeworks video games of the 2000s. Many fans speculate that this was due to budget reasons, evident by the abundant amount of Stock Footage in the film. It was later revealed however by Special Effects Director, Teruyoshi Nakano that the REAL reason it was never shown was because he didn't believe it fit with the character, so neither film demonstrated this ability for said reason. This all can be read here.
- Keep Circulating the Tapes: For a while, the only DVD release for this movie from Sony Entertainment was out of print. Fortunately, to coincide with the release of the 2014 reimagining, Kraken Releasing have re-released Gigan and two other Showa Godzilla movies on Blu-Ray and DVD.
- Its dub track, however, was not included on the Showa-Era set.
- Troubled Production: This movie had a long and complex path from its original script to theater screens, with major revisions being made constantly in order to stay within the meager budget. See What Could Have Been for details.
- What Could Have Been: The film had 2 different ideas that would up being turned into this movie and its followup:
- The first idea had Godzilla and Anguirus "team up" with a Rock Monster named "Majin Tuol" to fight Ghidorah, Gigan, and Megalon. Other differences that were to take place was that Godzilla Tower was just a base of operations for the heroes, the villainous leader behind the monster attacks was a floating brain named "Alien Miko", and Majin Tuol's only existence was to kill the Space Monsters (with the exception of Miko, who is killed by Godzilla). Megalon would go on to appear in the next movie.
- The second idea had Godzilla team up with Rodan and Varan to fight Ghidorah, Gigan, and a Dragon Monster named "Mogu". This idea was much more closer to the film that it is today, introducing the villainous Space Hunter Nebula-M aliens, as well as the monsters being summoned by tapes being played. The film also was to focus heavily on King Ghidorah, hence it's original title as "The Return of King Ghidorah". The idea was eventually dropped with the budget of making new suits for Rodan, Varan, and Mogu was too expensive (Varan's existing suit was already unsuitable for use due to how long it had sat in storage following his debut film, which necessitated a re-write of Destroy All Monsters), and Rodan's suit had been used in three movies in the 1960s) and instead were substituted for Anguirus, whose suit (Soshingeki Angira, made for Destroy All Monsters in 1968) was in good condition. This idea also was to give Gigan a Mace for one of his hands.
- The most financially successful of the 1970s Godzilla films.
Trivia / Godzilla vs. Gigan