Before it became a film, it was a six-part TV series, with Laurence Payne and Stuart Saunders reprising their roles from the series. In the original production, the creatures were named "Ixodes."
For its American release the film was cut to 75 minutes because American distributors wanted to get to the monsters faster. The film's full running time is 84 minutes and has been fully restored on the DVD release.
The Crawling Eye monster makes a literal cameo in Stephen King's horror novel "It." In a chapter set in 1958, the children encounter the creature in the sewer.
Quentin Lawrence also directed the original 1956 TV series on which the film was based, which was more than twice as long as this film version and did not include the film's main character, "Alan Brooks," in its cast list.
The bombers used to fight the Crawling Eyes are English Electric Canberras. These are British first-generation jet-powered medium bombers. They were developed by English Electric from the mid to late 1940s. They served in the RAF for more than 50 years.
It appears in the unreleased Misfits' Chiller Theatre Fiend Club Show (1996), hosted by Jerry Only and Doyle Wolfgang von Frankenstein of the Misfits, in which the films shown are discussed and guests are interviewed.