Although credited to Harry Essex, most of the script, including dialogue, is copied almost verbatim from Ray Bradbury's initial film treatment.
The Universal-International makeup department submitted two alien designs for consideration by the studio executives. The design that was rejected was saved and then later used as the Mutant in Universal-International's This Island Earth (1955).
According to a magazine article, the "bubble" effect when the audience is seeing things from the alien's POV was achieved by blowing a specially formulated "tough" bubble around the camera lens. These shots were kept short since the bubbles only lasted a brief time.
Kathleen Hughes was in only one scene with a couple of spoken lines, but she was included in the montage of featured players at the end of the film because she was Universal-International's potential answer to Marilyn Monroe, and the studio was grooming her for stardom.
The first 3-D film to be released by Universal Studios.