In 1986 actress Frances Drake recalled that the crew played a joke on star Karloff. They raised him up on a platform that was intended to lower him down into the radium pit. They raised him up high over the pit and left him there when they broke for lunch. According to Drake, the actor was a good sport about it.
The church in which Frank Lawton and Frances Drake get married, though called the "Church of the Six Saints" in the film, is actually the set of Notre-Dame Cathedral recycled from the 1923 Universal production "The Hunchback of Notre-Dame," starring Lon Chaney, Sr.
Boris Karloff, who was actually an Englishman (true name: William Henry Pratt), plays a Hungarian scientist. Bela Lugosi, who was actually a Hungarian plays a Frenchman.
The scene of Boris Karloff being lowered into the pit containing the Radium X meteor was reused in a 1939 Universal serial, "The Phantom Creeps," starring Bela Lugosi. Karloff essentially "doubled" for Lugosi in the sequence since in "The Phantom Creeps" it was Lugosi who was lowered into the pit.
Shooting lasted from Sept. 17-Oct. 25, 1935, release was held up due to the extensive special effects done by John P. Fulton. Issued January 10, 1936.
"Films in Review" devoted a lengthy retrospective article to "The Invisible Ray: A Reexamination:" by Richard J. Schmidt in its March 1986 issue.
Violet Kemble Cooper, who plays the mother of Boris Karloff's character, was less than a year older than Karloff.
Although Frank Reicher's character is correctly listed as "Professor Meiklejohn" in the opening credits, he is incorrectly listed as 'Professor Mendelssohn' in the end credits.
Part of the original Shock Theater package of 52 Universal titles released to television in 1957, followed a year later with Son of Shock, which added 20 more features.
We see newspaper front pages with dates of July 31, 1937; November 2, 1937; and November 13, 1937 (at 53:30, 1:00:50, and 1:01:30, respectively). At the time of the movie's release in January of 1936, these dates were a year and a half and more in the future. The purpose of this may have been to enhance the believability of the story's science-fiction premise, though one might wonder how many theater-goers noticed.
Early in the film, Janos Rukh projects a view of the Earth as seen from outer space. The sound effect of the meteor approaching the Earth was used continually by Universal Pictures as that of the rocket ships in its Flash Gordon and Buck Rogers movie serials.
The set for Dr. Rukh's laboratory appeared as that of Ming the Merciless in Flash Gordon (1936) and Countess Zelaska's castle in Dracula's Daughter (1936).
When Janos tells the man who resembles him he will do him a benefit, "the greatest man can do for another" he is indirectly referring to John 15:13: "Greater love has no one than this, that one lay down his life for his friends."