Space Amoeba

Ei Ogawa wrote the original script for this film in 1966 as a proposed joint production between Toho and UPA, under the title Great Monster Assault (怪獣大襲撃, Kaiju Daishūgeki). This script was considerably more ambitious than the finished product, featuring alien monsters invading the Earth and submerging entire continents. Production on the film did not begin until three years later in 1969, when the project first appeared on Toho's production lineup, still under its original title. Ogawa's script was heavily altered, removing the global scope of the original story and moving the setting entirely to the fictional South Seas island of Sergio Island. Producer Fumio Tanaka later said he believed the film went through three drafts, and stated that the original draft featured the alien invaders being attacked with nuclear weapons. Despite his failing health, Toho's longtime special effects director Eiji Tsuburaya expressed his desire to be involved with the production and as such was to be credited as the film's special effects supervisor, while his former pupil Sadamasa Arikawa acted as the director of special effects. However, Tsuburaya passed away just two days after the start of filming on January 25, 1970, and is only credited in early promotional materials for the film. Toho rejected a proposal by some staff members to dedicate the film to Eiji Tsuburaya. Arikawa was especially angered, refusing to talk about the film later in his life.

Gezora (Haruo Nakajima) comes ashore during filming.

The film's script was finalized in January, and shooting began that same month. Assistant director Seiji Tani remarked that Space Amoeba was burdened by constant pressure from the studio to minimize the budget, and that as a result the staff was forced to rush through filming. Ishiro Honda originally planned to shoot the film in Guam, but due to aforementioned budget restrictions shooting was relegated to Hachijo Island, located about 700 miles south of Tokyo. The film was shot in the middle of winter, even though the cast was dressed for a tropical location. Underwater scenes were shot in one of Toho's studio pools and Yomiuriland's Ryugu Palace. Producer Fumio Tanaka recalled that he had to personally transport the film negatives back to Tokyo on a prop plane. While Fumio Tanaka officially co-produced the film with Tomoyuki Tanaka, the latter was busy with Expo '70 at the time and as a result had very little to do with the production.[3]

Space Amoeba was the last science-fiction film made under Toho's studio system. Facing declining profits, Toho took several steps to reduce the power of labor unions: establishing a subsidiary called Toho Eizo to specialize in tokusatsu films, releasing most of its actors from their contracts, and dissolving Tsuburaya's special effects department. It would also be Honda's last film under contract with Toho, although he returned in 1975 to direct Terror of Mechagodzilla.