This was the first movie to feature King Ghidorah, who would later go on to be Toho's main villain monster, fighting both Godzilla and Mothra as well as making appearances on Japanese television.
This is the only film in the original Godzilla series in which King Ghidorah is not controlled by aliens.
This is the final film to feature the Ito Sisters (aka the Peanuts) as Mothra's twin priestesses.
The movie was for a long time unknown in European countries that otherwise used to screen Japanese monster movies, because for whatever reason, it was only released in a select few areas, such as Turkey, and only came to many of the other countries when the DVD was made available. As a result, the movie became far less popular in Europe than in the United States, since there was no nostalgia attached to it, and some viewers thought the film's comedic tone undermined Ghidorah's big debut to the series.
Because of its commercial success from King Kong vs. Godzilla, Toho decided to release another Godzilla film in 1964, Ghidrah, the Three Headed Monster. The Mosugoji suit, though, needed to go through some repairs. During the filming of Godzilla vs. Mothra, the mouth had become wobbly and would not work properly. The head had also caught on fire, which didn't help the suit much. So the head of the Mosugoji suit was replaced by a more sturdier design. "Mosugoji II," as some fans refer to the repaired suit as, also had more mobility than the original Mosugoji.
Rodan was originally introduced in the movie Rodan (1956), and would become a recurring character in the Godzilla films later on. It is never explained whether he is one of the original Radons (who apparently were killed), or a new specimen, although it is likely the latter.
First movie to depict Godzilla in a somewhat heroic manner. He would later gradually develop into a full-fledged hero.
Was released in the United States on a double feature with Elvis Presly's Harum Scarum.
If you look closely in the scene in the office of the UFO club's president, you will notice two miniature spaceship models in the background. Those are props from Battle in Outer Space (1959).
In Germany, the movie was only released in 2011. Following the odd dubbing traditions set up by the older German monster movie distributors, the title was changed to "Frankensteins Monster im Kampf gegen Ghidorah" ("Frankenstein's Monster's Fight Against Ghidorah") and the dub was made to sound deliberately cheesy.
When Godzilla first rises from the ocean, the costume appears to be the complete suit used in the prior film (Godzilla vs Mothra) which features a longer and more reptilian looking head. This does not match the head used for the monster throughout the rest of the film. Toho commonly used older versions of their monster suits when filming scenes that take place in water, in order to avoid wear and tear on the new featured costume.
In the original concept King Ghidorah was colored purple and his wings were rainbow colored. Also, the creature was to breath fire from it's three heads. In the final concept they emit lightning-like gravity rays and his skin is colored gold. Various publicity stills and promo material however still show parts of him in their original colors. On the movie's poster, only his body is colored gold, because the suit had not been finished when the shot was taken.
Eiji Tsuburaya originally wanted Ghidorah to be crimson colored, but the special effects team decided on shining gold instead, because that would have looked more impressive on screen.
Director Ishirô Honda originally wanted Yoshio Tsuchiya for the role of Malness. But he was unavailable due to his commitment to the Akira Kurosawa film Red Beard (1965).
Rodan is a bird of prey. When it first appears and the volcano tourists get on the buses, one of the buses has a nameplate that says "condor", another bird of prey.
In this sequel to "Mosura tai Gojira" (1964) Hiroshi Koisumi returns as Professor Miura. Yuriko Hoshi also returns as the female lead but she plays Naoko, a different character than she played in the previous film.
This was the first of two films in the series that Yôsuke Natsuki appeared in. Natsuke's next series appearance wouldn't take place until 20 years later when he appeared in Godzilla 1985 (1984).
The German dub of the movie pronounces Ghidorah's name as "Jidora", even though other German dubs pronounced it as "Gidora" or "Gidra".