Prudence Hyman was nearly decapitated for real. She was supposed to duck when Lee swung the sword but forgot to do so at the critical moment. The assistant director pushed her aside just in time. The scene was then redone with a dummy.
Christopher Lee is quoted in 'The Films of Christopher Lee': "Beautiful-looking picture, but the whole thing fell apart because the effect of the snakes on Megaera's head was not sufficiently well done for the climax of the film. Not a memorable film, but it could have been terrific."
Actress Barbara Shelley, who played the possessed heroine, Carla Hoffmann, wanted to play the part of the gorgon as well for continuity, and suggested to producer Anthony Nelson Keys that she use a special wig with live green garden snakes woven into it for a more realistic effect. Her idea was rejected by Keys due to budget and time considerations. When Keys saw the abysmal gorgon effects in the finished film, he told Shelley that he should have listened to her suggestion. As Christopher Lee quips, "The only thing wrong with "The Gorgon" is the gorgon!"
Although the UK cinema version was uncut some shots of the Gorgon's decapitated head were slightly darkened by the BBFC.
Double-billed with Hammer's "The Curse of the Mummy's Tomb."
Prudence Hyman's snake-filled wig was worked by five wires which were attached to a box that was about 25 feet behind her.
The name of the Gorgon character is "Megaera", supposedly taken from mythology. But Megaera ("jealous") in ancient myth is one of the three Erinyes, or Furies - the goddesses of revenge - not a Gorgon. According to Hesiod, the three Gorgons were Stheno, Euryale, and Medusa.