Orson Welles, who rose to prominence with his "War of the Worlds" radio broadcast of Halloween 1938, was pressured into making this his first feature film, but he wanted no part of it.
Lee Marvin was offered the male lead.
Ann Robinson hated the wig that she was required to wear for her role as Sylvia. When she finally saw the completed film at a theater, however, she claimed that no one recognized her without the wig.
Ann Robinson is the only member of the cast to reprise the same role in the 1988 TV series War of the Worlds.
Gene Barry and Ann Robinson appeared as the grandparents to the lead characters children at the end of the feature film remake "War of the Worlds" (2005). They were the lead characters in this version of War of the Worlds.
Cecil B. DeMille was due to direct the film when the rights were originally purchased in 1925, and Alfred Hitchcock was to direct a proposed version in the 1930s.
Cecil B. DeMille's personal choice to produce the film after Alfred Hitchcock declined to direct the film was George Pal, who was renowned for his Puppetoon animation technique and two earlier live-action sci-fi films: Destination Moon and When Worlds Collide. However, DeMille gave complete control to Pal over the production, and Byron Haskin was ultimately chosen to direct the film, a decision with which DeMille was pleased.
Albert Nozaki based his designs of the Martian machines on the shape and movements of manta rays.
A figure of Walter Lantz's 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 a Woody Woodpecker into each of his films.
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 listed on the theater marquee early in the film.
During the scene 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.
Filming was halted briefly, two days into filming, when Paramount discovered their filming rights to the novel were only for a silent version. It was quickly resolved through the kind permission of H.G. Wells's estate.
In an apparent homage to the famous Orson Welles's radio broadcast, 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.
In the theatrical trailer, when the first Martian meteor hits the Earth, there is a large explosion and a cloud of smoke. In the film itself, the same shot contains only a flash when the meteor hits.
None of the original Martian war machines exist today. They were made out of copper, and after production, they were reportedly donated to a Boy Scout copper drive.
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 next to 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.
Paramount Pictures had always wanted to put out a stereo version of The War of the Worlds on home video, but couldn't do so because the only archival sound elements they did not have from the film were the ones for the Martian ships. Luckily, the makers of the 1988-90 television series had to recreate the sounds of the Martian warships from scratch for the series, which Paramount used to finally create their stereo version of the science fiction classic.
Reportedly, George Pal wanted to do the final third of the movie in 3-D, starting with the sequence in which the atomic bomb is used unsuccessfully against the Martians.
The disintegration of Col. Heffner took 144 individual mattes. Earlier in the scene, the stuntman that portrayed the soldier catching on fire was badly burned from the flames getting out of control.