It's impossible to say that 1973's Godzilla vs. Megalon represents the flaming-out of the Godzilla franchise, or dropping off a cliff, or any other colorful metaphor you like for a movie series just plain giving up. After all, it came out just a year after Godzilla vs. Gigan, a movie which doesn't leave very much space for any more plummeting. And surely we have not forgotten Son of Godzilla, or the stock footage orgy of All Monsters Attack/Godzilla's Revenge.

So if I declare Godzilla vs. Megalon to be the very worst of the first phase of Godzilla films (and though I haven't at this writing seen them all, I really don't doubt that it's the worst Japanese-made Godzilla film, period), I'm really only talking about shading. And still, there's the age-old question, what means it for a movie to be bad, anyway? The outrageous unacceptability, on every level, of the script by Fukuda Jun, Sekizawa Shinichi, and Kimura Takeshi is obvious to behold and immutable, and the "shot in the backyard over the weekend" cant to the visual effects are nearly as undeniable. Yet it's so zany and bubbly in its non-stop ineptitude and idiocy that it is, at any rate, a whole lot more fun than the dismal Godzilla vs. Gigan, which found a way to make a Godzilla theme park boring.

Boring - that's one thing Godzilla vs. Megalon sure ain't. Which makes sense, given that it's basically the narrative equivalent of tapping into a preteen Japanese boy's id in the 1970s. It is important to note, before we go any farther, that the film began life as a totally Godzilla-free story which was to star Toho's newest suited hero, the winning entry of a 1972 contest in which Japanese schoolchildren were encouraged to submit designs to the studio. The winner was Jet Jaguar, a robot with a powerful resemblance to the popular and beloved Ultraman, for in those days giant monsters were on the wane and giant humanoid robots were ascendant. Initially, Jet Jaguar vs. Megalon was to be Toho's bid to capture some of that audience, and stay in the tokusatsu game as the economic validity of the daikaiju eiga was starting. At some point, however, somebody at the company blinked, and at the last moment, the decision was made to add Godzilla to the mix. This was in the form of stock footage artlessly snipped from the usual suspects (a whole lot of Son of Godzilla shows up), and also in the form a new suit built in a week - the shortest production time for any Godzilla suit in history. It was also in the form of a screenplay which was a goddamn trainwreck, throwing ideas into blender and hoping they'd stick, and instead of a plot we have what amount to a collation of zany, "cool" plot concepts strung along until the inevitable final-act battle where Jet Jaguar and Godzilla fight against Megalon and Gigan, the last of these showing up probably more because the suit was in good shape than for any legitimate, or coherent, narrative reason.

And so we have little boy Rokuro (Kawase Hiroyuki) living with his grown brother Goro (Sasaki Katsuhiko), an inventor putting the finishing touches on his new robot, Jet Jaguar. Also involved, either because he lives with them or because he's somebody's friend, or whatever, is Hiroshi (Hayashi Yutaka). The original Japanese version, which I'd never seen before, clarifies the Goro/Rokuro relationship a little bit more clearly than the English dub, but I still defy you to watch the film in any language and not be irresistibly drawn to the conclusion that Goro and Hiroshi are lovers, because there's literally no other interpretation that makes any sense based on the way human beings act. Of course, that's the secret: Godzilla vs. Megalon gives not a particle of a shit about the way human beings act, and if the point is to show a little boy living an insane life in an insanely production-designed house that seems based in robots and fun and goofing off with grown-ups, then that's what happens, regardless of any sensible reason for those grown-ups to be there.

Anyway. Jet Jaguar is coveted by the ruler of Seatopia (Robert Dunham), a long-lost civilisation under the sea, in a plotline cribbed blithely from Atragon. It seems that only the super robot can help to guide the apparently directionally-challenged subterranean kaiju Megalon, sort of like a beetle with blades for hands to destroy topside cities, for the Seatopians intend to do nothing less than destroy all our countries before we can use nuclear testing to further damage the planet. Naturally, the first country they intend to destroy on their anti-nuke rampage is Japan. From the sole above-water remnant of their country, Easter Island, they send out agents to incapacitate our heroes and steal Jet Jaguar. Luckily, the Seatopians are idiots and Goro has a back-up control, and instead of helping Megalon destroy Tokyo with the effects footage from Destroy All Monsters, Jet Jaguar flies to Monster Island to recruit Godzilla. The Seatopians call their alien buddies to send Gigan, and Rokuro and his friends which delightedly as Jet Jaguar reprograms himself to grow to giant size so he and Godzilla can beat the stuffing out of the bad monsters. And then Godzilla does this sliding kick using his tail as a runner, and it looks even dumber than the flying in Godzilla vs. Hedorah.

I just don't know what to do with this movie. It's so, so terrible; and so, so hilarious. Fukuda's direction reaches its natural peak here - turning the series into a live-action cartoon seems to have always been his instinct - and it is so wildly stupid and nonsensical that I can't even start to put into words how much affection I have for every asinine moment. A robot who can decide on the spur of the moment to increase in size by several orders of magnitude? Fighting a monster whose arms are metal blades and one whose arms are metal hooks? Please, yes. And more besides. The thing is so bright and bouncy and wacky in every respect of its design (Seatopia especially, the underwater city where monsters are raised by women in cellophane smocks dancing in circles), it's downright shrill. The complete abandonment of anything that even pretends to be pitched at an adult audience is infuriating and dazzling at the same time, from Rokuro's implausible house right up to the nutsoid Jet Jaguar theme song that brings the film to a merciful close, on the shoulders of a ludicrously cheery freeze frame.

The lack of care given is omnipresent, chiefly in the ridiculous, illogical plotting, but almost as clearly in the monster action. Outside of the plaguey All Monsters Attack, this is probably the worst action in any Toho daikaiju eiga: the broad mugging done by Komada Tsugutoshi and Odachi Hideto as Jet Jaguar and Godzilla, respectively, is already enough to completely trivialise anything that briefly hints at action (did you know, by the way, that you can mug through an opaque latex suit? Komada and Odachi figured out how to. Stunningly, neither man ever played any other role in a Toho kaiju film), even more than the Muppet-style google eyes the slapdash Godzilla is wearing already managed to. And I take back anything else I ever said or will say in the future: this is the worst Godzilla suit. The tail pretty fine; the spines are way too puffy, the proportions are a little less humanoid than the well-worn previous suit, but the face. It is unforgivable.

The fighting itself feels so much like kids brawling playfully that I take it to be deliberate; certainly, it's in keeping with the rest of the movie. And that means that, more than several of the other films in its direct vicinity, Godzilla vs. Megalon is a unified whole. That unity comes at the expense of sanity, class or anything that comes within a billion miles of the gravity and earnestness of the best, most impressive Godzilla films - it is, all in all, a ridiculous, sick joke at the expense of the character and the genre. But at least its nonstop panoply of the weird and crazy means that it is endlessly captivating from start to finish, if only in the manner of a spectacularly violent train derailment.