I feel slightly responsible for this because I read the original treatment and gave the feedback that it was unintentionally very funny – it was then turned into a weak intentional comedy.
The cast & crew finished Flesh for Frankenstein, went for lunch and haircuts, then started this in the afternoon. If you like one you'll like both, I slightly prefer the other.
Devastating satire of failed attempts to deal with disaster, spiced up with a grotesque body–horror take on Godzilla. Watch bureaucrats argue over which meeting room to use while Tokyo is destroyed.
Despite endless much more whimiscal sequels, this still works as an ellegory for nuclear destruction. The fact that the filmmakers witnessed the devastation first hand no doubt helped. The FX are actually better than in many of the subsequent films.