Ensemble Darkhorse: Hedorah has become a very beloved kaiju by the fanbase, mostly because of his genuinely creepy design, his powers and the fact he qualifies as one of Godzilla's strongest foes, giving the radioactive dinosaur a rather hard time in his debut.
Mood Whiplash: From intense fight against Hedorah and race against time to Godzilla flying backwards with upbeat music playing.
Narm: Godzilla flying backwards with his atomic breath.
Narm Charm: Typical with a Godzilla film but a special case is the Japanese 'Save the Earth' theme. The chorus of 'save the Earth' is weak during the movie's opening but by the end has grown in a strong and passionate chorus.
Nausea Fuel: The sludge in the bay, which was mostly real.
Nightmare Fuel: For the first time since the first Godzilla, human death is shown graphically. It's especially unsettling is that in one scene where a baby is shown drowning in Hedorah's sludge.
Hedorah himself. An alien lifeform that feeds on man-made waste and becomes stronger with it, his vaguely-humanoid looking final form that utters high-pitched menacing cackles is quite an horrifying sight.
Signature Scene: Anyone who knows anything about this movie knows about Godzilla's flight sequence.
Some Anvils Need to Be Dropped: In 1970s Japan, pollution levels were far worse than in the USA due to rapid post-war industrialization with no governmental checks. Despite its silliness, this movie was as relevant to the fears of 1970s Japan as the original was to the atomic fears of 1950s Japan.
Trash the Set: In addition to pouring ample amounts of chemical mixtures into miniatures and full-size sets, the 1965 Godzilla suit, first used in Invasion of Astro-Monster and used as a water scene suit since Son of Godzilla, was completely covered in sludge for the scene where Hedorah attempts to drown Godzilla. The suit was pulled out and cleaned up, but it had suffered so much damage through the years that it was finally given a well-deserved retirement.
Uncanny Valley: Hedorah, particularly in his final form. He looks vaguely humanoid, has creepy movements and his roar sounds like high-pitched, insane cackling, all of which are way too human-like to comfort.
Visual Effects of Awesome: Hedorah is arguably one of the better-portrayed monsters of the Showa series, with the movements of the monster himself eerily alien-looking.
What an Idiot!: Soooo the teenagers' plan to protest pollution is to drive their cars, which have been banned by the law, to Mount Fuji and lighting a huge bonfire in the middle of nowhere? Yeah, no wonder Hedorah showed up so quickly.