Continuity mistake: When Hermione is saying to Harry and Ron "You won't make a fool of yourself, it's in your blood," Harry and Ron have several books with them, but straight after, right before the staircase moves, they have no books in their hands. (01:00:35)
Continuity mistake: When Harry, Ron, and Hermione are in the staircases, watch the pictures on the right: they are not moving, but when the camera changes all the pictures are moving. (01:00:50)
Continuity mistake: When Wood takes Harry out to see the Quidditch balls, he sets down the bat right against the box holding the balls. When Wood goes to open the box, you see the grass where the bat should be. And then he picks up the bat, which is not where it was originally placed. (01:01:30)
Audio problem: When Harry, Ron and Hermione are running away from Mrs. Norris (the cat), Harry yells, "Quick hide through that door!" and if you look close enough you can see that his mouth doesn't move when he says that. (01:01:45)
Continuity mistake: When the three heroes first go into the forbidden corridor and are spotted by Filch's cat, they run away, through the large horizontal corridor which must be at least 40 metres long (since we are given two long shots of it and neither of them connects by any physical object). They hide behind a wooden door which they close afterwards. When Filch looks in the other end of the corridor then leaves and we hear a very silent click, Hermione says 'Filch is gone.' The door they're behind does not seem to be open at all, and even if it is open a bit on the right side, Hermione's on the left side of it so she can't see whether Filch is gone or not. And can you hear a silent click of a closing door from forty metres? (01:01:45)
Visible crew/equipment: Hermione opens the door to Fluffy's room when she says, "Alohomora!" so she, Harry and Ron could hide from Filch and Mrs. Norris. As Ron closes the door the top of the third floor corridor set is visible at the top of the screen. As an aside, when Ron repeats, "Alohomora!" look at Hermione's face. (01:02:00)
Visible crew/equipment: In the scene where Hermione, Ron and Harry are returning to Gryffindor's tower room after being in the third floor room for the first time, you are able to see the feet of one of the crew. It happens just as they are passing through the picture hole, where Harry turns a couple of times to check that the "door" is closing. And it is in fact, because someone is walking behind it and pushing it shut, since the picture hangs several inches off the floor. (01:02:55)
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)
Character mistake: When Wood is telling Harry the rules of Quidditch he says that if you catch the Snitch the game is over, which is true. But then he also says that which ever seeker catches the snitch, their team wins, but that isn't true. Granted that the 150 extra points probably would give you the winning lead, but as JKR pointed out in the 4th book at the Quidditch World Cup, you can catch the Snitch but lose the match. And you'd think explaining the rules to a first-timer you would want to get it right. (01:05:40)
Suggested correction: The team whose "seeker" catches the "snitch" would win in over 90% of matches. At this point, in the film and the book, while Harry Potter has discovered that Quidditch is popular in the wizarding world, he knows nothing about the rules or how to play. Oliver Wood is giving Harry Potter his very first introduction to Quidditch. So maybe it is acceptable for Oliver Wood to give a general overview of how Quidditch works, rather than outline every nuance and detail of every game ever played.
Visible crew/equipment: When Oliver Wood is explaining Quidditch to Harry, he struggles to put the Bludger back in the trunk. You can see a rod under the trunk lift and shake it, so the Bludgers appear to be moving on their own. (01:05:55)
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)
Audio problem: When the troll is about to swing at Harry for the third time with his club, Ron levitates his club in mid-air. When the club falls, it hits the troll's head with a loud thunk, then falls to the ground. But you never hear any sound of the club hitting the ground. (01:08:44)
Visible crew/equipment: After Quirrell announces there's a troll in the dungeon, Dumbledore shouts, "Silence!" and soon continues, "Teachers will follow me to the dungeons." In the following shot of McGonagall, the wires that the candles hang from are plainly visible. (01:09:00)
Visible crew/equipment: In the scene where Harry and Ron come running down the hallway and see the troll for the first time, you can see a floodlight at the top of the frame illuminating the area where they stop and hide. (01:09:30)
Continuity mistake: In the scene where Hermione is coming out of the bathroom stall her head is down and you can see that the part in her hair is crooked, but when she is under the sink you can see that now her part is straight. (01:09:55 - 01:10:50)
Continuity mistake: When Harry and Ron rush into the bathroom after the troll to rescue Hermione, they push open the closed doors, but wouldn't they be open from when the troll went in there moments before? The doors can't have closed after the troll as when Harry and Ron push open the door, it stays open. (01:09:55)
Continuity mistake: When the troll enters the girls' lavatory, in the wide shot as Hermione walks backwards towards the cubicles, the room becomes brighter from the storm. With this extra bright light it is simple to see that the wall between the 2nd & 3rd cubicles actually touches the floor, unlike the other cubicle walls. Yet, in the overhead shot as the troll's club slams into the cubicles, Hermione is lying under that very wall crawling away. (01:10:05)
Continuity mistake: When Hermione is confronted with the troll in the lavatory she backs up and runs into the cubicle. In the overhead shot as she locks herself in, the pattern on the floor that is visible in front of the next cubicle is different than the previous and following shots. (01:10:10)
Revealing mistake: At the start of the overhead shot as the troll's club smashes the cubicles, while Hermione lies on the ground, the top beams of all the cubicle walls and the front door of the second cubicle are all visibly pre-broken before the club slams into them. (01:10:15)
Continuity mistake: During the scene with the troll, Hermione crawls over to where the sinks are and if you look at the floor you will see that there are only a few wet spots. In the very next shot, however, the whole floor is soaked (this occurs before the troll breaks all the sinks). (01:10:40)
