The Nezura looked just like sewer rats since they were portrayed by them.
There was a Mammoth Nezura (マンモスネズラ), a giant mutant produced by Nezuras that were made to devour each other artificially. Mammoth Nezura was recreated for the film Nezura 1964.
Giant Horde Beast Nezura was an attempt by Daiei to capitalize on the monster movies going on at the time. Several still shots and promotional photos for the Nezura movie were produced and released, but the film was canceled by Kojima, the executive at Daiei, due to very bad conditions (lice, ticks and germs) brought on by the live, untrained sewer rats which they caught to shoot the movie, plus the worry caused for the neighboring town of Daiei Studios. The film is also infamous for killing a large number of rats in consequences, by burning, drowning, electrifying them alive including by an order from a health center. Noriaki Yuasa, the later director of Showa Gamera series, edited the trailer film for new year version. According to Toru Hirayama, Michio Mikami who is known for his later works including Kamen Rider series, suffered serious mite allergy to the point of near-death, and Mikami became dislike of rat monsters and didn't want to work for whenever rat monsters appeared in later works. The staff held a memorial service for dead rats at nearby temple.
Giant Horde Beast Nezura
At a Food Research Institute located on one of Japan's surrounding islands south of Tokyo, scientists develop a revolutionary high-calorie food source labeled the "S602." One of the scientists discovers the nutrient has terrible side effects that cause mutation in those who consume it.
Plans to continue with the experiments of S602 are halted and the current supply is supposedly disposed of. An infestation of rats on the island leads to a number of disappearances. An investigation uncovers giant rats attacking and eating livestock, as well as human victims. One of the dead man-sized rats is dissected for study, and a decision is made to spray poison gas on the island to kill all the rats.
Many of them escape to the sea and Tokyo is invaded by a horde of rodents as well as an enormous mammoth-sized rat. The rats eventually cannibalize each other, thus eradicating the threat on its own.
Nezurabatto (新怪獣ネズラバット?, lit. New Monster Nezurabat) is an unmade monster created by Mitsuo Murayama, who was to direct the original Nezura film. And unlike their 1964 counterparts, the Nezurabatto were to be winged, flying monsters. Shin kaijū Nezurabatto
- Just like Garasharp and Marukobukarappa, Nezura is an unmade monster who got a toy made for it.
- Some elements of Nezura and its scrapped film were incorporated into the 2002 Japanese film, Nezulla the Rat Monster.