Continuity mistake: At the end when Hercules comes back to Mt. Olympus, there are two huge lines of gods greeting him on either sides of a long staircase. After Zeus and Hera have talked to him, about ten gods start mobbing him. When the shot cuts back to Meg the staircase is empty. Where did all the other gods go?
Continuity mistake: In the scene where the gods are chained up and being led away, they keep changing places in between shots.
Continuity mistake: Inside the temple of Zeus, there is a huge ceramic design on the floor. But toward the end of this scene, the design has shrunk by an insane amount.
Continuity mistake: During the battle against the hydra, the hydra makes very distinctive scrapes on the ground with its teeth. After the battle, there is an overhead shot of the valley, and the scrapes are gone.