Revealing mistake: At the beginning when the ruler is making his speech, you can see his modern day fillings in his upper molars.
Continuity mistake: In the beginning scene, the ruler of Argos is condemning his daughter and son to the sea with a group of guards present at the shore. While he is giving his speech, there is a brief moment when the whole group can be seen getting drenched by a wave crashing ashore, but in the very next moment of his speech - even up to the daughter's cast off - no one is wet.
Continuity mistake: When they are fighting the giant scorpions, there are three distinct scorpions fighting. Each of the remaining men faces a scorpion 1 on 1. One of the men dies fighting, and thats the last we see of that scorpion. Thello kills his scorpion, then throws Perseus his sword who then kills his scorpion. The third one just magically disappears.
Revealing mistake: During the scene when Argos is being destroyed, a citizen falls backward due to the rushing waves and you can see a pair of black running shorts with white trim under his tunic.
Continuity mistake: When Calibos gives Andromeda the necklace, he drapes it around her neck (unable to clasp it with his long fake nails). In the next and following shots, the necklace is clasped.
Revealing mistake: When Calibos is speaking to Thetis' statue, as he screams "I demand justice", you can see the left horn on his head wiggling around, revealing a flimsy prop.
Continuity mistake: When it shows the man being burned at the stake in the city, the man is just a wooden carving. As brief as the shots of it are, it's extremely obvious, particularly if you use slow motion. (The use of slow motion is permitted when it reveals things such this.)
Continuity mistake: When Perseus is taming Pegasus, a claymation model is used for the long shots of the famous flying horse. However, when it shows Perseus jumping on the back of the real horse, you can clearly see that the horse has no wings. They couldn't figure out a way to strap on fake wings for the close-up?
Revealing mistake: When the ruler of Argos is cursing his daughter prior to setting her adrift, we are treated to a couple of close ups where his modern dental fillings are beautifully displayed.
Other mistake: When Perseus wakes up in the stadium and he is talking to the old man, you can see a flesh coloured pair of shorts under his tunic.
Audio problem: When Perseus starts to swing his rope at Pegasus, the rope is absurdly loud, and is obviously just the same recorded "whoosh" sound repeated four or five times.
Continuity mistake: After getting Pegasus back, Perseus hands the horse's rope lead to Ammon. In the following claymation shot, the rope has disappeared.
Deliberate mistake: After Perseus and his men defeat the scorpions, Kalibos goes after him, lashing his whip. But curiously, the whipping leaves no visible marks.
Other mistake: After Kalibos releases the scorpions to attack Perseus and the men, he starts wailing on the horses with his whip. He is obviously standing a considerable distance from the horses, yet shots reveal the whip striking a few of them.
Factual error: During most of the close action shots of Perseus flying on Pegasus, you should see some wing expansion, but do not - only during the wide pan claymation shots.
Revealing mistake: During the opening music score and credits, a seagull is flying and being followed by the camera. When the seagull gets to the rocky valley, it is obviously a black, drawn-in seagull and not the real thing. At one point, you can see the rock wall through the body of the seagull. (00:03:15)
Continuity mistake: Shortly after getting to Medusa's island, Perseus suggests to the three men with him to use the inside of their shields as mirrors. In this shot, the three men have the same insignia on their shields. However, when the two-headed dog attacks, the insignias have become different, not matching the previous ones. Even the surviving two men have unmatching insignias.
Factual error: Perseus and his mother would suffocate in the box within minutes. There were no openings for air.
Continuity mistake: When Perseus and the other soldiers are on Charon's boat, you see a couple of close-up shots of Charon's bony hands on the oar. However, in the long shots when Perseus is looking back at him, you can see that he has regular hands wearing gloves.
Continuity mistake: When Calibos stabs the bag containing Medusa's head, a lot of blood comes pouring out. Yet when the camera cuts to the ground, there is only a very small amount.
Answer: To me, it just looks like the way the prop catches the light as the actor lifts it up, and then higher up, the angle of the prop isn't catching the light in the same way.
Bishop73