Luce Potter, one of the Munchkins in The Wizard of Oz (1939), played the Martian "head" enclosed in glass in the film. For years she received letters from fans of the movie telling her how much she had scared them as kids.
The genesis of this film was when the wife of writer John Tucker Battle woke him up one morning to recount a vivid and disturbing dream she had of Martians invading Earth. He had her tell him as much as she could recall, and he developed the rest of the story from there.
In one scene, Dr. Kelston refers to the "Lubbock Lights" and to a "Captain Mantell." These were-real life U.F.O. events that created a nationwide sensation in their day. The photographs shown by Dr. Kelston are actual photographs of the Lubbock Lights that appeared in newspapers and magazines.
The special effects department used condoms to create the "bubbles" on the walls of the underground tunnels.
The eerie sandpit choir chant was done by a choral group made up of eight men and eight women, and was further enhanced with echo in post-production to give it a more haunting and ethereal quality.