It is fun to imagine there is someone in the world who has stumbled across Godzilla vs. Megalon expecting another serious reckoning with Japan’s nuclear holocaust, only to be confronted by a man dressed as a giant beetle body-slamming a bloke in a robot costume on top of a train set.

Toho’s 13th Godzilla movie continues the series’ descent into cheap cartoons for kids, even introducing a character (the mecha Jet Jaguar) designed by a child for a competition (presumably to see who could design the worst character). The franchise even seems to have softened its stance on nuclear weapons, basically positioning the victims of nuclear tests as the bad guys.

The 1973 entry sees the sunken civilisation of Seatopia unleash their beetle god Megalon on the surface world, in retaliation for the undersea damage caused by nuclear tests. It’s essentially Black Panther 2 except way more entertaining. Meanwhile back on land, a pair of inventors (Katsuhiko Sasaki and Yutaka Hayashi) and a child (Hiroyuki Kawase) have built a robot for some reason. Before you can say, “Are those two meant to be a couple?”, Megalon and Gigan are tearing polystyrene chunks out of Jet Jaguar and Godzilla, who is also in this film.

Godzilla vs. Megalon was apparently a last-minute replacement for a cancelled project, and the rushed schedule is evident in its cheap effects, unfinished script and flimsy Godzilla costume that was reportedly made in one week. The approach to the miniatures appears to have been, “why go to the trouble of building a model when you can buy a toy?”, and the results are about as functional as the insane pedalo we see at the start of the film.

Yet there is something distinctly charming about this ridiculous instalment, with its queer subtext, funky flute score (sampled by MF Doom) and quirky adventure plot that zips along for 80 minutes. And even that is padded out by low-speed car chases, which stay true to the film’s environmental ethos by turning off the engines and pushing the cars down a hill. Meanwhile the inventor trio are so engaging that we keep forgetting about the Seatopia storyline, until the movie hard-cuts to the aquatic Emperor in his silver toga, and the effect is funny every time.

The final showdown also overdelivers on its title by doubling the number of combatants, and Godzilla’s wrestling moves have come a long way since the rock-lobbing of 1962’s King Kong vs. Godzilla, now throwing tag-teams, tail-slides and weaponised trees into the melee. This all makes Godzilla vs. Megalon an enjoyable chapter in the kaiju saga, even if the best that can be said is that it’s not megalong.