Martine Beswick said that both she and Raquel Welch actually got along wonderfully during the making of this film. She also said that they were offered stunt doubles to do their cat fight scene in it, but she and Welch both insisted that they do it themselves.
Ray Harryhausen used his "Dynamation" stop-motion animation special effects technique in this film, but because producer Charles H. Schneer owned the brand name, Hammer Films could not use it in their marketing for it. However, producer Michael Carreras wanted to come up with a similar-sounding name for the process. After originally planning on shooting the film in Panavision (to which Harryhausen objected, as he, director Don Chaffey, and director of photography Wilkie Cooper preferred the regular spherical process that was favored by Harryhausen), Carreras, Hammer and 20th Century Fox attempted an amalgamation of the Panavision and Dynamation brand names into a new one, "Giant Panamation". However, the "Giant Panamation" name was dropped when the Panavision company objected to it. Some early press material for the film, however, did use the name.
Martine Beswick said in an interview that she did not even have to audition for this film. Being a Bond girl (in the James Bond films From Russia with Love (1963) and Thunderball (1965)) opened doors for her and Hammer Films thought that she should join their family, so they offered her the role of the cave girl Nupondi in it.
A poster of Raquel Welch's character of Loana from this film was featured in numerous other films and TV series episodes. One of the most famous examples of this is the film The Shawshank Redemption (1994).
As the Shell Tribe is attacked by a giant sea turtle, Loana calls it "Archelon", the real scientific name for the animal. The name is Greek and means "king turtle".