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)
Continuity mistake: When the movie begins and Merlin prepares tea for Arthur, the amount and shape of the cookies on the plate changes between shots.
Continuity mistake: During tea, after Merlin commands the couch to come walking, the books on the table change positions between shots.
Continuity mistake: When Merlin enters his place and pours water into the pot, the bookshelf behind has a bottle on the upper right corner. A shot later the bottle has been replaced for a thick book.
Continuity mistake: When the movie begins a squirrel sits on a tree with dry and broken branches. In the following shot the branches look different, with small branches having suddenly appeared.
Continuity mistake: The first shot of Merlin's house shows a dark green pot on the top of the shelf behind. A shot later it's dark orange.
Continuity mistake: The door of Merlin's hut is on the left when Arthur makes to leave, but is on the right after Merlin's packing song.
Continuity mistake: When Kay tells his father that he is now "Sir Kay" at the banquet celebrations in the castle, there is an eaten chicken and bones in front of him on the table that disappear in the very next shot.
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.
