To put things bluntly, Godzilla Vs. Gigan isn’t really about anything.
Oh sure, it has a PLOT (barely) but while it’s tonally scattershot predecessor, Godzilla Vs. Hedorah had a strong save the environment theme, Gigan simply can’t be fucked with all that bollocks and goes out of it’s way to cram so many explosions into it’s meager running time that ironically must have left a carbon footprint the size of Godzilla’s itself.
The good news, as if to combat this, is the filmmakers have gone out of their way to recycle as much as they can; the bad news it’s that it’s chiefly in the stock footage and plot department…
Yes, it’s the old space aliens mind controlling space monsters again (giant cockroaches assuming human form this time) but this time it’s not just the plot that’s second hand as sizable budget cuts forced sizable chunks of the action to be lifted from previous movies (hint, every shot of either Godzilla or Anguirus fighting King Ghidorah solo is old news).
And yet, unbelievably Godzilla Vs. Gigan, while not a great movie, is bizarrely watchable and this is primarily down to two things, the first being that the lack of quality in plot leads to an adventure that moves like a greased eel. The human stuff, aliens trying to take over the world by building a theme park (somehow) and are thwarted by two daffy freedom fighters and a comic book artist, is pure guff yet perky and nimble and the monster shit takes up the whole last third of the movie.
The second plus point is the debut of titular villian Gigan, one of the most mental monster designs in Godzilla history. A green, sickle handed, cycloptic, murder cyborg-chicken, armed with military-grade sadism and a buzz-saw in his belly, Gigan is one of my favourite Kaiju ever. Looking utterly ridiculous yet displaying vast amounts of personality, he really is a questionable joy to watch, whether trying to crack Godzilla’s skull like a walnut or rearranging Anguirus’ face with his razor sharp abdomen (seriously, Anguirus cannot catch a break), he’s a formidable fighter, a worthy Godzilla opponent and endearably excitable to boot, clashing his hooked appendages together with gleeful exuberance when things are going his way.
By this point the Godzilla franchise is firmly in the realms of so-bad-it’s-good territory with the artistic merits of the original movie nothing more than a vague memory but there’s still enough decent levels of undemanding fun to be had.