Of all the films in the nearly-60 year old Godzilla franchise, this is one of the most infamous. Criticized as being one of the worst and ruining the Big G's reputation, I'd call it an enormously guilty pleasure. Being a huge fan of Henshin Heroes such as Ultraman and Kamen Rider, I find the concept of Godzilla working with a superhero to be utterly delightful. Nevertheless, I AM analyzing this film on a critical basis.
The undersea kingdom of Seatopia wants retribution for the destruction caused by humanity's reckless use of nuclear weapons. To serve as their agent, they send forth Megalon, a giant beetle monster. Meanwhile, near a dam, young Rokuro Ibuki is playing with a water toy, when a mysterious earthquake occurs that nearly destroys Monster Island. When the dust clears, inventor Goro Ibuki is attacked by two Seatopian agents and the controls to his android are stolen (the film insists it is a cyborg... but Jet Jaguar simply does not fit the definition). The Seatopians use the controls to guide Megalon to do destructive deeds throughout Japan; however, Goro has a trump card, his voice-activated backup controller. He uses it to get Jet Jaguar to fly to Monster Island and summon Godzilla. The Seatopians decide to step up their game by calling for the cyborg monster Gigan to be loaned to them by the Space Hunter M Nebula aliens. Jet Jaguar grows gigantic and joins Godzilla in facing off against the two creatures.
The biggest problem with the plot is that it's too thin; however, this can be chalked up to the naturally formulaic nature of Sentai shows and heroes. This was largely a factor in why the film didn't do so well in theaters in Japan, why pay for something you can see at home? The Seatopians aren't too convincing as villains. Although sympathetic, the concept was pulled off much better in the classic Atragon (1963). As for the acting, it's not memorable at all. No one turns in an adequate performance, but the least I can do is give Jun Fukuda props for putting some effort into the stunt choreography early in the film. Wolf Otsuki is one of the more long-lasting actors here, and even appeared as late as 2003 in Super Sentai Abaranger. His stunts are fairly well done, thanks in part to the filming methods used by cinematographer Yuzuru Aizawa. As for the two lead actors, they're performances are completely boring. What is the relationship between Goro and Hiroshi? Are they friends? Cousins? The film just throws these characters in with little exposition.
The effects fare fairly better. Although much of the destruction sequences are stock footage from the previous films, the newly filmed dam destruction sequence is an impressive feat. Teruyoshi Nakano has said he always takes extra care with fire and water, and it shows; however, it's not nearly as impressive as his work in Submersion of Japan (1973). The battle sequences are nicely filmed and choreographed, and it's a real shame there wasn't a bigger budget to work with. I'd say the effects are the highlight of the film, but that isn't saying much considering what's come before.
Finally, we go to a love-it-or-hate-it topic, Riichiro Manabe's score. As a musician myself, I am intrigued by the variety of instruments used by Manabe in his compositions. I personally find the military themes very intriguing. One sounds very formidable and could be put to a force of invading aliens with much the same effect. The other sounds almost like a parody of the famous Dragnet march, especially mocking when Megalon destroys the maser tanks; it plays rather dullish. I also like the theme song of the film, “Godzilla and Jet Jaguar Punch, Punch, Punch!” sung by one of my personal favorites, Masato Shimon. Bringing his usual energy into the theme, it's actually quite nicely composed. This score also carries the rare privilege to have a few tracks on my MP3 player, especially the serene and rather fitting “Highway Road”. It's a nice, if somewhat dated theme, using lots of flute and a unique guitar passage; it runs for a brisk minute. One aspect I dislike is the infamous Godzilla theme. Played rather comically on the trumpet, it's not very fun to listen to. Overall, I think the score is a nice break from the famous Akira Ifukube themes.
Final thoughts, I feel the film isn't as bad as people say it is. I find it enjoyable, like the average Ultraman or Sentai episode. However, the plot and acting, not to mention the overuse of stock footage, make the film not that great in comparison to other films in the series.