Goofs

Francesca (Jane Asher) uses a candle at the beginning of her walk but not as the walk continues.

At the beginning, when the Man in Red calls Grandmother to come closer, he is looking at her, but in the next shot isn't.

When Red Death moves his hand above the white rose which becomes red, he obstructs the view of the rose, but in the next shot of the rose becoming red, his hand is not seen.

When Francesca says she doesn't want to learn (harsh lessons), the shot is clearly discontinued from the previous one, which can be seen by difference in positions of her and Prospero and the lighting.

The use of an inverted cross as an anti-Christian or Satanic symbol is largely a creation of 20th century movies. The cross is known as the Cross of Saint Peter, who was one of the Twelve Apostles. When he was to be crucified Peter asked to be done so upside down as he was unworthy to die in the same way Jesus did. During the Middle Ages and Edgar Allan Poe's time it was a holy symbol no Satan worshiper would use.

Despite Prospero warning the guests not to wear red to the masque, several people are wearing red: capes, hats, etc.

People ignoring someone's directions is not a Goof; it happens all the time and was even a significant plot point in Jezebel (1938).

When guard is thrown to the wall, the wall shakes, revealing it is fake.

When Francesca (Jane Asher) awakens from her nap, she picks up a green candle from the bedside table and uses it to light her way in spite of the fact that the room is not dark. Despite the heavy wind blowing in from the open balcony, the flame of the candle does not blow out.

When Gino is climbing the castle wall, the whole wall shakes, revealing it is fake.

Towards the end, just before Prospero sees the man in red, a blonde woman dances from left to right. The frame then jumps, and the blonde woman is once again on the left side without having returned.

There is a clear discontinuity between shots just before Prospero takes off the mask from the Man in Red's face.

True to Roger Corman's penchant for utilizing anything already available in the studio to dress his actors and sets, many of the men's hats are 300 years out of date with the time period that the story is supposed to have taken place in.

Many of the women were low cut dresses. Not only was this impossible at the time, but this also would have marked them as loose women, and no women of the time would have worn a dress so revealing.

The gorilla suit used in the film is obviously a modern prop made in the 1960s and wouldn't have existed in the time the film takes place.

When Francesca, Gino, and Ludovico escape the dungeon, they encounter Prospero waiting for them outside. Prospero immediately states that Gino and Ludovico will have to answer for killing three of his guards while escaping the dungeon below, but as he was outside, there is no way for Prospero to know if the guards were killed. The guards could have been merely injured and not killed, or bribed, or they could have let them pass without a fight.

Prospero gives "Belial" as an alternative name for Satan. In virtually all sources, this is the name of a demon, not Satan himself.