Yumi Shirakawa's singing voice (for the two songs in the film) is provided by noted Japanese jazz starlet Martha Miyake.
In the original Japanese version, the detectives make a big deal out of the fact that Chikako owns a television. At the time this was made, 1958, a television set was still beyond the budget of the typical Japanese family.
In the U.S. theatrical release,and subsequent TV release prints, "The End" appears on screen in Japanese as in the original Japanese language version. For the 2009 U.S. DVD release, the final seconds are jarringly replaced with a title card that reads "The End" in English.
The dissolving effect was created by deflating life-sized inflatable human figures, filming them in fast-motion, and then running the film at normal speed.
On the lobby floor in some theaters where the H Man was a coming attraction, a melted victim was on display -- it consisted of a pair of shoes with shirt and pants and a toupee piled on top.
In some first-run theaters, the early guests in line received an H-Man toy of unknown description.
Haruo Nakajima had two roles. One was "second dissolved sailor", another was "Liquid Human Being".
Yasuko Nakada was considered for the role of Emi, the dissolved dancer.
For the U.S. release through Columbia Pictures, one of the items available for a promotional giveaway was an H-Man made of a compressed sponge in the shape of an "H" that would swell up when wet. Most exhibitors foresaw the danger of a kid armed with a compressed sponge in the vicinity of a nearby restroom or water fountain.
Among the footage deleted from the U.S. English dubbed version was a musical number in the nightclub scene involving a scantily clad dancer that was considered a little too daring for American screens at that time.
In the original Japanese version, after the stock shots of the hydrogen bomb tests, the title, cast and credits are matted over shots of the "ghost ship" in Tokyo Bay. For the U.S. English dubbed version, the title, cast and credits are matted over a shot of an H-Man in the sewer system. Since there are fewer cast and credits on screen in the U.S. version, Masaru Sato's opening score was skillfully edited into a shorter version.
In 2008-2009 Columbia Pictures undertook a restoration of their U.S. English dubbed version. Because this film was very popular, some of the pre-print material had become badly worn. Columbia had to get replacement elements directly from Toho.
To create Columbia's English dubbed version, some of the printing of the original Japanese footage was manipulated. For the final dialog in the film, there was even a very brief freeze frame (the same frame of film being printed multiple times) so that Koreya Senda's lip movements would seem to closely match Dr. Maki's required final English (dubbed) dialog.
Like the original "Gojira" (1954) ("Godzilla"), the story was inspired by the fate of the Lucky Dragon Number 5, a Japanese fishing boat that sailed into an atomic test area. Instead of confronting a giant creature, this story has the crew transformed by radiation into a race of "liquid creatures" that subsist on humans.