Flah Scenes

When Andromeda wakes up to find Perseus has left for the Isle of the Dead without her, we see her from behind standing and looking in the direction he's gone, and her long hair is tucked in under the blanket around her shoulders. When we see her from the front, her hair is clearly pulled out from under the blanket and blowing in the wind.

Anachronisms: As the destruction of Argos begins, heavy winds blow the tunic of a man pulling a donkey on a rope to reveal a pair of modern-day gym shorts underneath
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Revealing mistakes:

• When Perseus follows the Vulture carrying Andromeda through the air, there is a shot that shows the Vulture flying over the city. Two peasants can be seen walking up a hill at the bottom of the screen. When Persus enters the screen from the top left, riding Pegasus, the two peasants suddenly disappear and instantly reappear a few steps back, then repeat their walk up the hill. In the much later scene when Perseus rides Pegasus to save Andromeda from the Kraken, the same two peasants are briefly visible in the exact same position.
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  When Perseus tames Pegasus, in the close-up of him jumping onto Pegasus' back, it is clearly an ordinary white horse, not the winged Pegasus.
  Continuity: During the fight with Dioskilos (the two-headed dog), Perseus slashes its right neck, leaving a large, bloody wound. When Diokilos falls off the ledge, the wound disappears, and then reappears in the next shot.
  Anachronisms: When Perseus is invisible, he leaves footprints which are those of modern shoes, not sandals.

Later on in the movie, when Perseus and his guards are fighting the two-headed wolf, his two guards put a slash in the cheek of the wolf. There is a brief splash of blood shown on the left head of the wolf on the right side of its face. Then a couple seconds later, the blood is completely gone.
Continuity: When Calibos releases the scorpions from the Medusa's head, there are three of them. One kills a soldier, one is killed by Thallo and one is killed by Perseus. Then the fight ends. The one which killed the soldier disappears mid-battle.

Factual errors: In the scenes after Perseus leaves to go on his journey, in some of the shots, the soldiers are wearing the proper Grecian helmets. However, in other shots, the soldiers are wearing helmets that would have been worn by Roman Centurions.