Douglas Hall's house has been seen before in several other science fiction films: as the exterior Detective Deckard's apartment building in Ridley Scott's Der Blade Runner (1982), and several years later as the apartment of a drug lord in Predator 2 (1990). Located in the affluent Los Feliz neighborhood of Los Angeles, the home is known as the Ennis-Brown House and was designed by legendary architect Frank Lloyd Wright.
The science fiction novel "Simulacron-3" was also published under the title "Counterfeit World," and was first published in 1964 by Daniel F. Galouye in the United States, making it one of the first literary descriptions of 'virtual reality.'
While the movie was a box office bomb, its theme song 'Join Me in Death' (or simply'Join Me' in the U.S.) by HIM became a world wide smash hit.
Right at the beginning of the film, around 2:10, Fuller/Grierson is seen in 1937 timeline tipping a girl with a bunch of 20 dollar notes, amounting to around 200 dollars. Adjusting for inflation, it would amount to around 4k to 4,5k USD in 2024 money. Also, the average weekly salary for a worker in 1937 was about 20 to 30 dollars, which makes the tip roughly one-and-a half-month worth of work.