Gigan

Gigan debuts in the 1972 film Godzilla vs. Gigan, in which it and King Ghidorah are summoned to Earth by the M Space Hunter Nebula aliens, insect-like aliens whose planet had been ravaged by another race and wish to subjugate the Earth in order to create a utopia of "perfect peace". However, the monsters are challenged and defeated by Godzilla and Anguirus.

Gigan

In the 1973 film, Godzilla vs. Megalon, Gigan is sent by the Nebulans to assist the people of Seatopia in their assault on humanity by aiding their god, Megalon, in a battle against Godzilla and Jet Jaguar. After having its arm broken by Jet Jaguar however, Gigan retreats into space, leaving Megalon to face Godzilla and Jet Jaguar alone.

In the same year, Gigan also makes an appearance in Toho's television series Zone Fighter. After his battle with Godzilla and Jet Jaguar, Gigan is captured by aliens called the Garogans and sent back to Earth to prevent Godzilla from rescuing Zone Fighter. It was temporarily defeated by the former, but revived once Godzilla left and faced Zone Fighter, who eventually killed Gigan.