Continuity mistake: When told to relax in the Devil's Snare, Ron's hands keep changing positions instantly. (01:52:00)
Continuity mistake: When Quirrel collapses in the great hall on Halloween, his feet are quite far apart. Camera cuts to everyone rushing for the door, and Quirrel's feet are practically touching. (01:05:30)
Continuity mistake: When Harry is telling the others that Snape gave Hagrid the dragon's egg, there is a group of older people walking towards them. They start to pass Harry, the camera changes angle and they are just starting to pass Harry again. (01:47:50)
Continuity mistake: In Harry's first Quidditch match, Gryffindor scores the first goal, then we see the commentator announce the goal and change Gryffindor's score to ten - making a goal worth ten points. Soon after, Gryffindor score again. We then see Slytherin score a goal, then another. They then score a third goal, and the commentator changes the score to 20 all, but it should be 20/30. (01:17:40)
Continuity mistake: When Hagrid goes to leave, the door has a gap visible at the top where you can see the rain. When Hagrid grabs hold of the top of the door the gap has vanished. (00:17:20)
Continuity mistake: When Fluffy drools on Ron, the amount of drool changes drastically. (01:51:30)
Continuity mistake: The amount of shirt that is untucked on Ron just after their exams is constantly changing from a lot to a little. (01:46:20)
Continuity mistake: When Neville first takes off during the 1st flying lesson, Ron covers his face with his right hand. When the shot changes, his hand is no longer over his face. (00:54:20)
Continuity mistake: On his first night in the castle, Harry is sat on a window ledge with Hedwig. In this shot, his feet go from resting on their sides and crossed at the ankles to flat and uncrossed. (00:48:50)
Visible crew/equipment: As the first years amass at the top of the steps prior to being sorted, a strong, round white light is in the glass behind McGonigal. (00:38:10)
Continuity mistake: When we first see Harry drawing a cake in the dirt, his hand is in the shadow created by the sofa when lightning strikes. When we see a closeup of the drawing, his hand is in the light. (00:12:50)
Continuity mistake: When the letters start flying through the letterbox they are coming in with the address facing down and the red seal facing up. When Vernon says they are going away, the letters are now addressed side up and red seal down. (00:12:15)
Visible crew/equipment: When Dumbledore gives the order to the students to follow the Prefects towards their dorms after the troll came out from the dungeon, just a moment before Harry warns Ron that Hermione is unaware of what is happening, some light reflectors simulating lightning are reflected on the glass above the pathway where the students come from. (01:05:55)
Revealing mistake: When Ron is hit by the Queen during the chess game, the stunt double is visible on the horse just a few moments before he falls. (01:59:00)
Other mistake: Albus Dumbledore's name is spelled incorrectly on his card (after the chocolate frog escapes the container). It's spelled with an "E." (00:36:00)
Continuity mistake: In the scene following Harry's sorting, Hermione has changed sides at the Gryffindor table. (00:43:00)
Continuity mistake: In Olivander's shop, the packages Harry put down when entering the shop change position between shots. (00:24:30)
Revealing mistake: When Harry, Ron and Hermione are making their way back to the Gryffindor common room, Ron says 'She knows more about you than you do', to which Harry replies 'Who doesn't?' The "solid brick" staircase moves so that they have no place to go but the third floor forbidden corridor. If you pay attention to the staircase it can be seen that there is a good gap between the staircase and the one it connects to when it moves and that when Harry, Ron and Hermione run off the staircase to the corridor the staircase made of "solid stone" does an awful lot of shaking. (00:58:40)
