Orson Welles, who rose to prominence with his "War of the Worlds" radio broadcast during the evening before Halloween of 1938, on Sunday, October 30th, 1938, was pressured into making this his first feature film, but he wanted no part of it.
The Martian war machines were originally going to be walking tripods as they were depicted in H.G. Wells' novel, but George Pal didn't know how a tripod would walk and instead went with the flying machines.
The sound effects of the Martian war machines' heat ray were created from three electric guitars played backward. The sound of the Martian screaming after Forrester hit it was a mixture of a microphone scraping along dry ice and a woman's scream played backward. The former set of sound effects became widely used stock sound effects after the film was released. They are still in use.
The Martian war machines had about twenty wires running to each one. Some were for suspension and maneuvering, while others carried power to the various lights and mechanisms. This was produced before there were lightweight circuits and sophisticated radio controls.
Paramount Pictures always wanted to put out a stereo version of The War of the Worlds (1953) on home video, but couldn't do so because the only archival sound elements it did not have from the film were the ones of the Martian ships. Luckily, the makers of the War of the Worlds (1988) television series had to recreate the sounds of the Martian warships from scratch for the series, which Paramount used to finally create its stereo version of the science-fiction classic.
In one of the montages of destruction in the film, Martian fighting machines were superimposed over black and white footage of a lava flow destroying buildings in and around Naples, Italy, during the 1944 eruption of Mt. Vesuvius.
The prologue of the film shows paintings of the other planets in the Solar System, which the Martians examined and rejected as being unfit for habitation, finally selecting the Earth. The planet Venus, however, is neither shown or mentioned. The paintings were made by Chesley Bonestell, as famous astronomical painter whose works were often published in books on astronomy and space travel in the 1950s.
Filming was halted briefly, two days into filming, when Paramount discovered that its filming rights of the novel were only for a silent version. It was quickly resolved through the kind permission of H.G. Wells's estate.
Originally, the Martian war machines were supposed to walk on visible electronic beams. This was attempted by having electrical sparks emanate from the three holes at the bottom of the machine. This was quickly abandoned for fear of it becoming a major fire hazard. The first two shots of the first war machine emerging from the gully has this effect. During filming, the actors were under the impression that they were dealing with the walking tripod machines of the book. This explains the farmhouse scene when Gene Barry says, "There's a machine standing right along side of us." However, the results of the walking can be seen wherever the Martian machines fly throughout the film even though the sparking effect was no longer used.
When Major General Mann first meets Dr. Forrester, he refers to an earlier meeting in Oak Ridge. This refers to Oak Ridge, Tennessee, which was the home to three Manhattan Project plants that enriched and refined uranium during World War II for use in the first atomic bombs. Of the three, one (K-25) was in use until 1985, and one (Y-12) was still in operation as of 2010.
George Pal initially planned to portray the Martians and their fighting machines similarly to how they appear in the original novel. However, after being informed by a United States Army technical adviser that the Tripods as they are portrayed in the 1897 novel would pose no real threat a 1950s era human military, he opted to change the fighting machines. Namely, Pal chose to introduce the atom bomb-resistant deflector shields.
In the farmhouse when the Martian fled from Clayton and Sylvia, Charles Gemora, who had to control the Martian by kneeling in the costume, almost fell out of the back of the suit when one of the workers pulled the platform on which the Martian was kneeling out of the shot too fast. If you look closely at the scene, you can see the Martian is tipping over slightly.
Although the exact location of the first Martian landings isn't clearly identified, geographical references in dialog from the film would place it in the Puente Hills, about 25 miles due east of Santa Monica adjacent to the Pomona Freeway, south of West Covina.
By way of acknowledging the part that Cecil B. DeMille had played in bringing the story to the screen, George Pal wanted him to narrate the film, but DeMille suggested Sir Cedric Hardwicke instead. Pal also paid tribute to DeMille in the film by having his film Samson and Delilah (1949) listed on the theater marquee early in the film.
A figure of Walter Lantz's most popular character, Woody Woodpecker can be glimpsed in the branches of the tree the initial Martian cylinder meteor flies over. Lantz and George Pal were close friends and Pal always worked an appearance of Woody Woodpecker into each of his films.
In an apparent homage to the famous Orson Welles's radio broadcast, on Sunday, October 30th, 1938, when the hatch of the Martian machine begins to unscrew, the same technique, a metal lid being turned on a glass jar, was used to create the sound effect.
Production of this film was completed just as the transition from Academy ratio to wide screen was taking place. For this reason, though the film was shot at an aspect ratio of 1.37:1, and in fact was shown in the UK in this format, for US domestic release it was shown theatrically at the aspect ratio of 1.66:1.
Two of the characters from Orson Welles's 1938 radio broadcast (portrayed in the film by different actors), Professor Pearson (the main player in the radio broadcast), and the ill-fated journalist Carl Phillips made brief appearances at the site of the first Martian landing, in New Jersey, on Sunday evening October 30th, 1938.
The trivia items below may give away important plot points.
The disintegration of Colonel Heffner took 144 (a gross) individual mattes. Earlier in the scene, the stuntman who portrayed the soldier catching on fire was badly burned from the flames getting out of control.
The scripture Pastor Matthew was reciting before being disintegrated by the Martians is Psalms 23 of the Original King James Version of the Bible. (Before different versions were created, replacing old English with 21st Century English. 4 SAMPLES: Thou = You. Yea = Yes. Wot = Know. Ass = Donkey.)
The Martian machines were models suspended from wires. For the final sequences where the machines die, they are shown crashing into telegraph poles - this allowed the filmmakers to hide the suspension wires with the telegraph wires.