The special eye effects for Steve March were created by having John Agar wear special black contact lenses that were very thick. The extreme thickness of the contact made it painful for Agar to wear them.

Vol promises to defeat Gor, saying, "I have powers that equal and surpass the powers of Gor." But when it's time to put up or shut up, Vol stays out of it; his only "help" amounts to telling Sally to wait until Gor materializes and then hit him over the head.

Director Nathan Juran insisted on being billed as "Nathan Hertz" (Hertz was Juran's middle name), apparently because he was embarrassed by this film's low budget and poor quality.

Although some sources list Morris Ankrum as being in the cast, he does not appear in the film.

Brief clips from this movie are used in the opening credits on the sitcom Malcolm in the Middle

First credited role for Robert Fuller.

Dan is reading "Space Science Fiction" Vol.1 No.2 August 1957 issue. Part of the cover showing the word "Space" is ripped off. Boris Karloff can be seen on the back cover.

Vol tells Sally that Gor's weak spot is the "fissure of Rolando" and the encyclopedia diagram confirms this, but Sally twice mispronounces it as the "fissure of Orlando". There is no such thing as the "fissure of Orlando". However, there is an area of the brain called the "fissure of Rolando". It is the central sulcus, or fold, in the cerebral cortex.