Inventor Goro Ibuki creates a humanoid robot named Jet Jaguar. It is soon seized by an undersea race of people called the Seatopians. Using Jet Jaguar as a guide, the Seatopians send Megalon as vengeance for the nuclear tests that have devastated their society.
as Inventor Goro Ibuki
as Hiroshi Jinkawa
as Rokuro 'Roku-chan' Ibuki
as Japan Special Defense Forces Chief
as Lead Seatopian Agent
as Seatopian Agent
as Truck Driver's Assistant
as Man from Unit 1
as Emperor Antonio of Seatopia
as Truck Driver
as Antonio's Aide (Radio Operator in White)
as Godzilla
as Megalon
as Jet Jaguar
as Jet Jaguar
as Gigan (as Kengo Nakayama)
as Emperor Atonio of Seatopia (voice)
as Narrator
as Godzilla (archive footage) (uncredited)
