Continuity mistake: When Snape is insulting Hermione on being a know-it-all while he is substituting for Lupin, he has a slide show running. The shot shows Hermione with the projector behind her. The projector now changes slides fully and stops moving. When the shot changed back to Snape, the slide is still changing. It could not be the next slide because the slide changes every few seconds. (00:53:00)
sdgirl98
5th Jan 2005