There is a notable resemblance between the characters of Jimmy and Gigantor and the characters of the boy Hogarth and the giant robot in Ted Hughes' well-known children's book The Iron Man, which was published in 1968. It is not known whether Hughes ever saw the Gigantor series.
In post World War II and then Cold War era Japan, it is likely that the plots for the episodes were symbolic of the things going on in the world at the time. This assumption can be made given how many plots revolved around one oppressive country invading another peaceful one, requiring Gigantor's aid to save them. It is debatable whether or not the writers meant for the oppressive country to be representative of the United States (Like many writers of the time did in the Japanese genre of giant monster and robot heroes) or of the Soviet Union, or even both. The same is true in the reverse, as peaceful countries could be the United States or symbolic of a country under the 'Iron Curtain' (Both would fit with the Soviet Union being portrayed as the oppressor) or as Japan itself (Which would fit if the oppressing country was the United States). Curiously, Gigantor's size, facial features and European knight-style armor suggest that the robot itself may have been inspired, at least in part, by Japanese perceptions of foreigners.
Ladd, who had produced the successful international, English-language adaptation of Astroboy, and Al Singer formed a corporation called Delphi Associates, Inc. in order to produce and distribute an English-language version of Tetsujin-28-gō. They took only 52 episodes of the Japanese series for the American market, and renamed the series Gigantor. Peter Fernandez wrote much of the English script, and participated in the dubbing. The series became an immediate hit with juvenile audiences, though adult reactions were sometimes hostile.
It was playing at 7:00 p.m. on New York's WPIX-TV in January 1966 when Variety gave it a particularly scathing review, calling it a "loud, violent, tasteless and cheerless cartoon." which was "strictly in the retarded babysitter class."
Even this reviewer, however, had to grudgingly admit the popularity of Gigantor, writing, "Ratings so far are reportedly good, but strictly pity the tikes and their misguided folks.
Gigantor became a popular Japanese export during this time. The series was shown on Melbourne television in January 1968 through Trans-Lux, on Channel 10 at 5:00pm. It was described by the TV Week as an "animated science fiction series about the world's mightiest robot, and 12-year-old Jimmy Sparks who controls the jet-propelled giant." The series was also screened in New South Wales (presumably around the same time) on the 0-10 Network's Sydney affiliate. It was also screened in New Zealand around the same time.
Gigantor was one of a number of Japanese TV series that enjoyed strong popularity with young viewers in Australia during the 1960s. The first and undoubtedly the most successful of these was the hugely successful live-action historical adventure series The Samurai, the first Japanese TV series ever screened in Australia, which premiered in late 1964. It was followed by a contemporary ninja-based live action espionage series, Phantom Agents, and a number of popular Japanese animated series including Astro Boy, Prince Planet, Marine Boy and Kimba the White Lion, the cartoon series which is reputed to have been the uncredited basis for Disney's The Lion King.
In July 1994, Fox Family Films, a division of 20th Century Fox, acquired the rights to "Gigantor" for a live-action motion picture. Anticipating that Gigantor would become a franchise for the studio, Fox tapped screenwriters Steve Meerson and Peter Krikes to prepare the script and budgeted between $35 million and $50 million for the film. Executive producers Fred Ladd and Aeiji Katayama indicated that Mitsuteru Yokoyama would get an executive producer credit and that the 50 foot robot would be updated and modernized for the 1990s with a 12 foot height and morphed and computer-generated features.
Jimmy Spark's voice was that of Billie Lou Watt. The voice of Inspector Blooper was that of Ray Owens. Gilbert Mack voiced Dick Strong. Peter Fernandez provided the voices of other Gigantor characters.
Creators behind Gigantor have unveiled plans for another updated design, a "Gigantor for the New Millennium." This newest form of the giant robot is called G3 and differs from past designs. The new Gigantor is a meld of robot and cyborg. According to the main site: "Driven by a complex neuro-system of DNA-impregnated neurochips, Gigantor G3 is a living Cybot!" ".