Concealed in the depths of the great lands of Seatopia, a living god sleeps. Laying in slumber within his sculpted frame, an untapped power that is unequalled coleuses. Revered as the symbol of Seatopia's Kingdom, the giant was worshipped daily. But the prayers in his name were never as strong as when the people of the undersea city challenged war against the surface dwellers. Calling and pleading with the creature, they shouted for revenge on the lands of Japan. For their ignorance, the human race will die, and their blood would run in great torrents in flashing rivers. Screaming for their savior, the god awoke and shrieked into the sacred lands. Then, in a blinding act of speed, took to the air, and began his ascension to the surface. It did not take the insect beetle long to tunnel through the layers of rocky strata, and soon he made his presence felt. Attacking with unrelenting fury, tanks, jets, and men met their fates. All being crushed at the burning standards of the rampaging creature.
Shinji Takagi (Godzilla), Kenpachiro Satsuma (Gigan), Tsugutoshi Komada (Jet Jaguar) and Hideto Odachi (Megalon) rehearse their fight scenes in a school's gymnasium.
Godzilla Vs. Megalon was originally planned as a non-Godzilla film, a solo vehicle for Jet Jaguar, which was the result of a contest Toho had for children in mid-to-late 1972. 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. The robot was renamed Jet Jaguar and was set to star in Jet Jaguar vs. Megalon, which pitted him against Megalon. However, after doing some screen tests and storyboards, Toho figured Jet Jaguar would not be able to carry the film on his own, either in screen appearance or marketing value, so they shut the project down during pre-production. Nearly a month later, producer Tomoyuki Tanaka called in screenwriter Shinichi Sekizawa to revise the script to add Godzilla and Gigan. To make up for lost production time, the film was shot in a hasty three weeks. The production time totaled at nearly six months, from planning to finish.
According to Teruyoshi Nakano, the Godzilla suit made for this film (known as the Megaro-Goji) was made in a week, the fastest featured Godzilla suit ever made to date. Godzilla was portrayed by stunt actor Shinji Takagi.
There are, interestingly, no major female characters in the movie, making this the only Godzilla film without a female lead.