Wikipedia
, also known as the Smog Monster, is a kaiju monster who first appeared in Toho's 1971 film Godzilla vs. Hedorah. The monster was named for , the Japanese word for sludge, slime, vomit or chemical ooze.
Whereas Godzilla was a symbol of Japanese concerns over nuclear weapons, Hedorah was envisioned as an embodiment of Yokkaichi asthma, caused by Japan's widespread urban pollution at the time. Director Yoshimitsu Banno stated in an interview that his intention in creating Hedorah was to give Godzilla an adversary who was more than just a "giant lobster" and which represented "the most notorious thing in current society". He also stated that Hedorah's vertically tilted eyes were based on vaginas, which he considered "scary". The monster was originally going to be named "Hedoron", though this changed once the TV series Spectreman introduced a character with an identical name.
The monster was realized via various props and a large sponge rubber suit donned by future Godzilla performer Kenpachiro Satsuma in his first acting role for Toho. Satsuma had been selected on account of his physical fitness, though he stated later that he had been disappointed to receive the role, as he had grown tired of taking non-speaking roles. In performing as Hedorah, Satsuma tried to emphasize Hedorah's otherworldly nature by making its movements seem more grotesque than animal-like. Several authors have noted that, unlike most Toho monsters, Hedorah's violent acts are graphically shown to claim human victims, and the creature shows genuine amusement at Godzilla's suffering. Banno wished to bring back Hedorah in a sequel set in Africa, but the project never materialized, as he was fired by Teruyoshi Nakano, who accused him of ruining the Godzilla series. The character was nevertheless generally well received, with WatchMojo.com listing Hedorah as #7 on their "Top 10 Godzilla Villains" list, while Complex listed the character as #8 on its "The 15 Most Badass Kaiju Monsters of All Time" list.
Banno had hoped to resurrect Hedorah in his unrealized project Godzilla 3-D, which would have had the monster renamed "Deathla". Like its predecessor, Deathla would have been a shape-shifting extraterrestrial, though it would have fed on chlorophyll rather than gas emissions, and all of its forms would have incorporated a skull motif.