Continuity mistake: The letters A and B on the bottom row on the blackboard differ styles between shots, being wobblier in the second shot.
Continuity mistake: Before Kay cuts the mop's handle, the mop is dark brown. After he cuts it turns to vanilla coloured.
Continuity mistake: When Merlin searches for the model plane the knot holding it swaps from neat to crappy between shots. (00:56:02)
Continuity mistake: When Ector and Kay fight, the mallet behind turns 180ยบ. (00:49:30)
Continuity mistake: When the movie ends, the way the curtain on the right folds changes between shots.
Continuity mistake: The teapot with the flower at Mim's place keeps swapping back and forth between being next to the window and sitting on the centre of the windowsill.
Continuity mistake: The position and pattern of the playing cards on Mim's table keeps changing in every single shot.
Continuity mistake: At Madam Mim's, the cup and saucer on the table moves around between shots.
Continuity mistake: When Arthur is scrubbing the cauldron, a pot next to it disappears and reappears between shots. Also, the grip of the handles of the bucket behind him swap between round to square.
Continuity mistake: When Merlin arrives from the future, he talks about it to Arthur and puts the crown on his head. The sword, resting against the throne, appears and disappears randomly all the time.
Continuity mistake: When Arthur takes the sword out of the stone, Hector stands in front of Kay. A shot later, they're both next to each other.
Continuity mistake: When Ector walks Merlin to the tower, the bones on the floor by the door disappear between shots. (00:20:47)
Factual error: When Merlin and Arthur are squirrels Merlin says squirrels mate for life, which is not true. Squirrels are promiscuous.
Character mistake: Archimedes says he told Arthur not to pull the sword out of the stone. He didn't, he pointed it out in the churchyard to him instead.
Suggested correction: Archimedes was trying to be helpful when he pointed out the sword so Merlin could take it to the tournament. But after it became a big issue with the rays from heaven and the legend, Archimedes thought he might get in trouble so tried to act innocent by fibbing. It was deliberate and in character, not a character mistake.
