Continuity mistake: As they fly over Hogwarts Express Ron yells, "Take my hand!" the corner rubber trim of the door frame is peeling up. When Ron grabs hold in the shot facing Ron, their hands are positioned differently than in the next close-up where it's visible that the frame of the door is fairly clean, there are two parcels behind the seat, etc. Yet when Ron grabs hold after Harry says, "...Your hand's all sweaty," the rubber trim is fitted into place, the frame of the door is filthy and there are different parcels behind the seat, etc. (00:25:20)
Continuity mistake: As Ron and Harry watch in the background, Crabbe and Goyle hold cupcakes that change position, then start eating Hermione's cupcakes. When the close-up faces Crabbe, the little bit of cupcake in Goyle's hand is visible. However, when Goyle rolls his eyes up as he begins to fall backwards, the cupcake in his hand is nearly whole. (01:19:10)
Continuity mistake: As Aragog approaches Harry and Ron, Harry says, "Were friends of Hagrid's," and Harry carries the lantern palm side up, at his hip. Yet in the next shot, it's palm side down and the lantern handle is at his shoulder. In the next shot, though it's still at his shoulder it's palm side up now. Then in the two shots facing Aragog, the lantern is down low, but in between those two shots, in the shot facing Harry, his elbow is bent, the lantern is higher up and Fang stands further away. (01:45:15)
Continuity mistake: In the scene where the Chamber finally opens, we first see Harry, Ron and Professor Lockhart from the front, and Harry and Ron are slightly behind Lockhart, and in a position to threaten and guard him. When you next see them a moment later from behind, Lockhart is behind them and they are in no position to guard him. (01:58:45)
Visible crew/equipment: In the Dueling Club scene, as Snape says "Don't move, Potter, I'll get rid of it for you" and walks towards the camera, a film crew chair can be seen on the left side of the screen.
Continuity mistake: There are eleven vertical front bars on Harry's window, five on each side of the center bar. Ron attaches the hook to the bars on Harry's window and when he says "Let's go!" we see the hook between the third and fourth bar on the right. Yet in the next shot and also in the shot looking up as the bars fall, the hook is between the fifth and sixth from the right. (00:09:20)