Visible crew/equipment: After leaving Borgin & Burkes in Knockturn Alley, Harry is accosted by a witch. When he begins to turn around, just as the bald man approaches, the actors' mark is clearly visible on the edge of the first deep step below, with the shallow steps in the background. In the shot from above, after Hagrid says, "What do you think you're doing down here? Come on," their mark is GONE. (Visible on DVD fullscreen.) (00:16:35)
Visible crew/equipment: In Flourish and Blotts, after being spotted, the photographer pushes Harry behind the desk and Lockhart pulls Harry closer. At the start of this shot, the books lying on the floor, on the left, are visible under the desk. There are two strips of white tape, perpendicular to each other, on the floor protruding from under the books. However, in the overhead shot when Lockhart says, "..is currently celebrating its 27th week...," their mark is GONE. The tape is visible again when Lockhart says, "..with my entire collected works...," due to the same camera angle as the first. (Visible in DVD fullscreen) (00:18:35)
Visible crew/equipment: When Harry, Ron and Lockhart are in the girls' lavatory, Harry speaks Parseltongue to open the Chamber. Lockhart then tries to escape so the boys push him back. In this shot the white strips taped to the small black mat, which itself is taped to the floor for Rupert's mark, are plainly visible at his feet. (01:59:20)
Revealing mistake: When Harry and the Weasleys are standing on Platform 10, it is Ginny's turn to go, in this shot Ron's trunk is clearly visible, note the stains, the latch hardware on the right long side, the corner hardware at the four corners, etc. After Mr. and Mrs. Weasley go, Harry says, "Let's go!" and as they begin to run, Ron's trunk is clearly seen again and it is NOT the same trunk, note the stains, the lack of hardware at the right, no hardware at the four corners, etc, plus the small parcels near Scabbers are different too. (00:22:30)
Visible crew/equipment: After Harry says, "Rictusempra!" Malfoy is thrown across the room and lands at Snape's feet. Snape grabs Malfoy at the back of his neck and as he pulls him up, Alan Rickman's mark, the green tape, is visible at his feet, as well as Tom Felton's white tape mark at his left foot. Whereas in the earlier shot, when Snape suggests someone from his own house and says, "Malfoy, perhaps," the end of the mat is visibly without any marks. (Not visible in DVD widescreen format) (01:06:25 - 01:07:40)
Revealing mistake: In Hagrid's hut, while Ron is still slug sick, Hagrid is comforting Hermione over Draco's mudblood comment. His beard is visibly detached below his lower lip and when he speaks his jaw moves while his beard does not. (00:41:15)
Visible crew/equipment: In the three shots facing Lockhart as he continues to say, "It is my job to arm you against the foulest creatures known to wizardkind... Know only that no harm can befall you whilst I am here," there is a WIRE attached at the bottom left of the cloth that lies on the pixie's cage. However in the close-up of the cage, as Lockhart removes the cloth, the bottom of the cloth is clearly visible and the wire is gone. (00:35:55)
Revealing mistake: After the car shows up to save Ron and Harry from the spiders, Harry shouts, "Arania Exumai!" The light from his wand illuminates the car and the NORMAL tread back tire is visible. When they are in the car Harry shouts, "Go!" In the close-up of the tire, before it starts to spin, the tread on the tire is once again visible. However it's an entirely different tire, a deep tread SNOW tire no less. (01:48:10)
Other mistake: While downstairs Vernon hears Hedwig's squawks, as well as Dobby and Harry's exchange in the bedroom upstairs, distracting enough for them all, including the Masons, to take note. The noise upstairs illicits a reaction from everyone, which Vernon explains is a noisy cat. Yet when Harry very noisily chases Dobby down the steps, Dobby slams into the wall and Harry lands with a loud thud (not remotely 'catlike'), Vernon, who stands on the other side of the shared wall, pleasantly continues his story to his rapt guests, who are also not distracted by the noise. To suggest that such loud noises coming from the hallway right beside them would not draw any reaction from anyone, Vernon and the Masons included, is preposterous. (00:06:45)
Revealing mistake: As Harry climbs the Salazar Slytherine stone head's locks of hair, the Basilisk crashes his face and creates the first immense hole. As Harry tries to climb higher, it pounds into the stone again creating another huge hole, higher up on another lock of hair, to Harry's left as he hangs on. However, when the Basilisk smashes his face into the stone a third time, as Harry nears the top, the second huge hole is GONE, in this shot and in the first wide shot in which Tom Riddle is visible. (02:13:05)
Visible crew/equipment: While Harry is in Dumbledore's study, in the two semi-overhead shots as Lucius Malfoy says, "So it's true. You have returned," and later when he says, "Come Dobby, we're leaving," sitting on the floor directly behind Dumbledore is a large STEEL piece of the crew's equipment, plus in the second shot another piece of equipment actually moves in front of the steel piece. (02:21:35 - 02:23:35)
Other mistake: In the ending credits, the character of Hannah Abbott is listed as "Hannah Hufflepuff."
Suggested correction: That is because the viewing audience (well in a deleted scene anyway) only heard her first name of Hannah and knew she was a Hufflepuff by her robes. This was done intentionally, not to say her last name is Hufflepuff, but so the audience would know who this is in reference to. Not everyone in the viewing audience is a die hard Harry Potter fan who would know that's Hannah Abbott with her last name not being said.
Revealing mistake: The Ford Anglia's front seats keep changing. When Ron, Fred and George are rescuing Harry from the Dursleys, the front passenger seat has a curved thin back and is very dark blue with light blue trim at each side. However some examples when it differs are, as Harry hangs from the car while flying over Hogwarts Express, though the seat has a curved back, in some shots the seat is two shades of light blue and in others it is as in the shots at the Dursleys. Yet at Hogwarts, when the car ejects Hedwig, the back of the seat is thick and perfectly sraight and so on. (00:09:35 - 00:25:05)
Revealing mistake: When Harry stands at his bedroom window looking at the nearing headlights, the houses opposite him on the left are really the neighboring houses that are seen to the left of the Dursleys when facing the Dursley house and the one on the right is actually the Dursley's home. In the close-up of the car as its headlights face Harry, the Dursley's house is seen behind it, but the check curtains and patio table were added to change the look of the house. The distinctive pattern of each of the home's bricks are a giveaway. (00:08:30)
Revealing mistake: When the limb of the Whomping Willow crashes through the back window of the car, the hole changes shape in certain shots. In the first interior shot, as the branch goes through, the hole that is made is completely different than in the next exterior shot, as the tree branch leaves. (no pun intended) (00:27:20)
Continuity mistake: The pillow and blankets on Harry's bed not only change position in consecutive shots, the actual pillow changes drastically from the time Dobby jumps up and down on the bed, until Harry confronts him about the letters. (00:03:05 - 00:04:30)
Continuity mistake: When the flying car throws Harry and Ron out of the car, and Harry is lying on the grass, you see that he starts to get up, but in the next wider shot he is starting to get up again. (00:28:10)
Continuity mistake: After Harry has caught the Snitch and is sitting up, Hermione runs over to him and kneels in the sand next to him. Her robes are covering her knees in a long shot, but as it cuts to a close up her knees can be seen, and this continues to switch for the next couple of shots. (00:57:55)
Continuity mistake: After Harry packs his trunk, in the wide shot, as Ron starts to lean over to attach the hook to the bars, the excess rope is in the corner of Ron's window, but in the next close-up it's right in the center. (00:09:10)
Continuity mistake: As Harry chases the Snitch after his arm is broken, he reaches and catches it in the shot facing him. In the next side shot, as he begins to roll over while still balancing on top his broom, the attached foot rest is visible between his thighs. However, when he rolls under his broom then skids to the ground, it is clear that the foot rest is gone. Whether the foot rest is in the open or closed position, it would still be visible either above or below his leg. (00:57:20)