Trivia

While the film was all but ignored in Japan, becoming the least attended entry at the box office, it was a huge hit in the United States and is often regarded by fans as one of the main reasons why the Godzilla franchise has become so misunderstood in the west. Its American distributors, Cinema Shares International, built up a large advertising campaign around the movie, and a drastically shortened version that cut the film down to around 40 minutes premiered on prime-time TV on the NBC network. The film's VHS releases were also mistakenly believed to be in public domain, which made it more easily accessible and adding to the movie's notoriety in the US. Despite the film being disliked by the majority of fans, the movie actually received positive reviews from critics upon its initial release in the States. Vincent Canby praised Godzilla's development stating that "the dragon has become St. George" and wrote that the film "demonstrates the rewards of friendships, between humans as well as monsters, and it is gentle." Variety also praised the special effects work and the miniatures work as superb and "reflecting a creative understanding of the camera". The English film critic Phil Hardy also lauded the film's visuals as expertly done.

Gigan's design was noticeably altered compared to the previous film. This is because it's an entirely different suit, as the original supposedly got too damaged. He now has a much larger head and a less fierce expression, he has golden scales around his neck, his limbs appear shorter, his back sails are pointier, and he looks overall stockier. He doesn't demonstrate his signature buzzsaw embedded into his torso either (apart from stock footage), since that function was removed from the suit. This version of the suit was used for Gigan's appearance in the television series Zone Fighter (1973).

Jet Jaguar was the earliest example of a fan-service in a Godzilla film, the result of a contest Toho had in mid-to-late 1972 for children to come up with a new hero for them to use (to capitalize on the many super hero shows that were all the rage at the time). The winner of the contest was an elementary school student, who submitted the drawing of a robot called Red Arone, which superficially resembled both Ultraman and Mazinger Z (1972) (both of which were very popular at the time). The robot was redesigned and renamed "Jet Jaguar", with the new design being deliberately made to look unattractive and obnoxious. It is often incorrectly stated that Jet Jaguar was set to star in a film vehicle for him, titled "Jet Jaguar vs. Megalon,". However this is not true, as the film always meant to be a Godzilla project that would introduce Jet Jaguar. Staff mentioned that the film seemed to take forever to develop, around six months, only for production to quickly begin without enough preparation.

Aside from playing the Seatopian Emperor Antonio, Robert Dunham, who was also a stuntman and vehicle racer, also played one of the two "Unit 1" Seatopian Agents (he was the one on the motorcycle) in one of the car chase scenes (where he and another agent were chasing Yutaka Hayashi's character). The last shot where he gets splashed with cement was done with another actor, because Dunham had to get to the studio that day to record his part, and didn't want to have to get cleaned up on the way.

Megalon's ray beam is animated the same way as King Ghidorah's gravity beams. This was made to ensure that stock footage from Ghidorah's movies could easily be interspliced between shots of Megalon firing his beam.