Revealing mistake: Actress Yvonne deCarlo's palms and insides of her fingers do not have her green makeup applied like on her face, arms, etc.
Other mistake: When Sir James examines a book on witchcraft in the Vicar's library, it is a photographic reprint (more contemporary to 1966) of a much older, original book.
Continuity mistake: At the beginning, Aldo escapes at precisely 3:00. But when driving away, they pass a store-front clock which reads 12:30.
Continuity mistake: Didi is wearing a long black negligee when Pepe throws her into a bubble-filled bathtub on a movie set. When she gets out of the tub and runs off, the negligee has disappeared and she is covered only with bubbles.
Visible crew/equipment: After Matt's arrested at the discotheque, when he's at the police station with Julian, the chalk actor's mark can be seen on the floor in front of Matt's feet.
Continuity mistake: When the four kids uncouple the coach from the engine Carole is wearing trousers. The stationmaster tells them to stand clear as the engine pulls away, in the first shot of the children after the engine has gone Carole is still wearing her trousers but in the second shot Carole is now wearing a skirt.
Visible crew/equipment: During the flashback scene in the clock courtyard, there are multiple T-marks (plastic type) visible on the ground, near Col. Marcus and Gen. Randolph. (00:16:20)