Tohl Narita: “It feels like a birdman.”
It is known that Hydra was designed after the real-life statue that appeared in the show. It is a statue named Kōgenryū (literally, “wild field dragon”) that still remains in existence at the Izu Shaboten (Cactus) Park (Hydra’s alias is Kōgenryū in the show as well, but it means “plateau dragon” with a different Chinese character used).
As to how this statue was chosen for the show, Yuzo Higuchi, director of this episode, plainly says in a book that they found it by chance during location scouting. Things were often decided in such an easy-going way back then while I love it.
Hydra was sculpted by Ex Production instead of Ryosaku Takayama who should have already been extremely busy in making Narita-designed Ultra Kaijus one after another.
Ex (representing “expert”) Production pronounced as “Ekisu Purodakushon” or abbreviated as “Ekisu Puro” in Japanese was formed by the founders including Masao Yagi and Keizo Murase who had been involved in the sculpting work for Toho tokusatsu movies such as Godzilla.
It seems to have been when Ex Production was just established that the order was placed with them for the Hydra costume. Murase founded his own sculpting company in 1972 called “Twenty” (written and pronounced as “Tsenny” in Japanese) known to have made the massively sculpted costumes of Vakishim and Verokron for “Ultraman Ace.”
Among other things, it is said Vakishim was too large to take out of the workshop and that they had to sever the costume temporarily for delivery to the studio.
According to Murase, Hydra’s scales all over the body were made from an artificial leather material by cutting each piece apart and pasting them over each other.
He says they made scales for King Ghidorah by casting the latex pieces from the mold, which enabled them to give the scales more solidity with the center part of each piece slightly elevated while the same method could not be applied to a TV show kaiju due to the budget and schedule.
The Hydra costume was remodeled into Guigass by Ex Production afterwards. In the 1970s, Ex Production and Twenty seem to have played their active roles in sculpting characters mainly for the shows featuring human-sized heroes such as Kamen Rider and Kikaider.
Incidentally, it is likely that Izu Shaboten Park has changed its name into Izu Shaboten Zoo Park (Izu Shaboten Dobutsu Koen) with the Kōgenryū statue remaining as it had been.