The Abominable Dr. Phibes (1971)

Factual error: In keeping with the theme of the Ten Plagues of Egypt, Doctor Phibes has one of his victims eaten alive by locusts. Not likely. Locusts are strictly herbivorous, and like all herbivores locusts won't touch anything that moves. They would not be attracted by the slimy goo poured over their 'victim', because they zero in on plant pheromones and nothing else.

Plot hole: The police Inspector recounts the murders, comparing them to the ten Biblical plagues of Egypt, and he states that in keeping with this theme Dr. Kitaj was killed by rats. First, Dr Kitaj dies in a plane crash. Okay, he was attacked by rats in flight but nobody would know that - his plane crashes in a huge, violent fireball and nobody would find any rat remains after that. Second, there was no plague of rats in ancient Egypt! (Go ahead, look it up). Even if the police had made the connection between the mysterious deaths and the ancient plagues they would not make the connection here.

Revealing mistake: When the bats invade Dr. Dunwoody's bedroom, you can see the strings on one of them.

Trivia: The film's original tagline was "Love means never having to say you're ugly!" in a play on the famous line "Love means never having to say you're sorry..." from the film "Love Story."

TedStixon

Trivia: The bats that eat one of Phibes' victims are actually "played" by flying foxes, which are a very peaceful type of fruit bat that don't eat meat (outside of some insects) and are typically very docile.

TedStixon

Trivia: Phibes was originally much more devious and unlikeable in the original script, but his character was slightly mellowed out in subsequent drafts, which made his motives clearer and based on losing his wife, and removed any violence not aimed at his targets.

TedStixon

Dr. Anton Phibes: Where can we find two better hemispheres, without sharp north, without declining west? My face in thine eye, thine in mine appears, and true plain hearts do in thee faces rest. Within twenty-four hours, my work will be finished, and then, my precious jewel, I will join you in your setting. We shall be reunited forever in a secluded corner of the great elysian field of the beautiful beyond.

Sgt. Schenley: Well I have discovered they all have one thing in common.
Inspector Trout: If you say they've all died mysteriously I'll bloody kill you.

Dr. Phibes: My love, sweet Queen and noble wife. I alone remain to bring delivery of your pain. Severed my darling, too quickly from this life. Of fires drawn and memories met, I shall hold our two hearts again in single time. Nine killed you. Nine shall die. Nine times, nine! Nine killed you! Nine shall die! Nine eternities in DOOM.

Question: One of the doctors Phibes blames for his wife's death during an operation is Dr. Hargreaves, whose head is crushed inside a frog mask during a costume ball. But earlier, while introducing himself to Phibes, Dr. Hargreaves says he is a psychiatrist ("headshrinker"). Why would a psychiatrist be present during an operation to save someone's life?