Continuity mistake: When Snape enters the classroom during the first Potions class, there is a lit candle and an hourglass on the desk directly behind him. But in the following shots the candle and hourglass change positions and move farther away. (00:49:20)
Continuity mistake: As Hagrid aims his 'umbrella' at Dudley while he eats Harry's birthday cake, in the side shot one end of the blue string (that was tied around the cake box) hangs down the side of the table, but when Vernon rushes Petunia and Dudley off, in this shot that end of the string lies on top of the table. Yet, when Hagrid says, "We're a bit behind schedule. Best be off," the string hangs off the side again. (00:17:30)
Continuity mistake: When Madame Hooch approaches and then welcomes the class to their first flying lesson, the angle at which their shadows are cast changes dramatically in consecutive shots throughout this scene; and in some shots there are no shadows. (00:55:00)
Revealing mistake: Just after Harry gets back on his broom, the Slytherine seeker chases the snitch and he passes towers of (in order) Gryffindor, Hufflepuff, Ravenclaw, Slytherine, Gryffindor and Hufflepuff, on his left (this means Hogwarts is also to his left), when Harry flies up beside him. However, next shot as Harry slams into him, they still fly in the same direction, and the school is now on their right. Mistake with the background plate. (01:22:00)
Continuity mistake: The size and style of the writing on the envelope from Hogwarts at the starts changes depending on the shot. When Uncle Vernon picks it up, the word "stairs" is a fair way from the edge of the envelope. When he flips it over and you get a close up, the same word is a lot closer to the edge. (00:08:50)
Continuity mistake: After Voldemort's soul flies through Harry, he crashes down on the stairs and his hand sticks out over one of the steps. In the next shot of Harry lying there, his hand no longer lies over the step. Harry is knocked out and could not have moved. (02:13:20)
Audio problem: When Hedwig flies from Harry's arm, or owls deliver mail, you hear the sound of wingbeats. However, owl's feathers are specially adapted to allow for completely silent flight. See here for an explanation. http://www.owlpages.com/articles.php?section=Owl+Physiology&title=Feathers. (00:53:45)
Continuity mistake: When Harry lifts the mail from the floor at the Dursleys, the Hogwarts envelope flap is sealed shut and it has the red wax seal at the tip. Yet in the kitchen after he hands Vernon the other letters, Harry holds the Hogwarts envelope and though the red seal is on the back, the flap itself is NOT sealed shut. The wax seals differ in both shots as well. (00:08:45)
Continuity mistake: The way in which Mr. Ollivander holds out the second wand for Harry to try differs, in the shot facing Mr. Ollivander and the next shot facing Harry. (00:26:25)
Revealing mistake: When the mail comes, Ron receives the Daily Prophet and Harry asks, "Can I borrow this?" As Harry asks to borrow the newspaper, the Malfoy body double is plainly visible over Ron's left shoulder. (00:54:10)
Revealing mistake: After Madame Hooch takes Neville to the hospital wing, Malfoy takes the Remembrall and mounts his broomstick, on a convenient protruding metal rod. Then when he comes around, though the students step away and watch as he begins to fly off, many of their eyes are not level with Malfoy, as he is merely edited into the end of this shot. (00:57:50)
Continuity mistake: After the final confrontation Harry has scratches on his face, particularly one on his chin. When visited by Prof Dumbledore the chin scratch is barely there but in the scene in the refectory it is back and appears larger than before. (02:14:00 - 02:17:50)
Continuity mistake: As Hermione walks toward the troll, just before she asks, "Is it dead?" the long towel hanging from the rod beside the sinks is visibly straight. When Harry lifts his wand with troll booger/bogey, in the shot of him as he grimaces and groans, the towel on the rod is visible behind him and it's messy. Yet when McGonagall, Snape and Quirrell walk in, the long towel is straight again. (01:12:00)
Continuity mistake: When Madame Hooch leaves with Neville to go to the hospital wing, Seamus holds his broomstick with the bristles on the ground as Malfoy ridicules Neville. However, as Malfoy steps on his broomstick and then flies away, the bristles on Seamus' broomstick are now at the top. Then when Harry takes off on his broomstick, the bristles on Seamus' broom are on the ground once again. (00:57:30)
Continuity mistake: When Malfoy first talks, the window behind him is bright blue. He says "it's true then, what they are saying on the train, Harry Potter has come to Hogwarts." Everyone says "Harry Potter" and when it cuts back to Malfoy, the window is much much darker. Both a mistake in terms of continuity between windows, and also a mistake because we'd seen everyone turn up in total darkness earlier, so the window shouldn't have been lit in the first place. (00:40:30)
Continuity mistake: At the end-of-the-year feast the Slytherin banner is green and gold, but their house colors are green and sliver, as evident by their robes. (02:11:00)
Continuity mistake: At the hut on the rock, Harry lies on a grey blanket spread on the ground between the fireplace and the couch. When Hagrid bangs on the door, Harry quickly jumps up and hides, leaving the blanket behind. Though the blanket is visible on the ground, in some shots, it is however, gone in the three wide shots with the Hagrid body double, as he zaps a tail on Dudley, then as all the Dursleys run upstairs, as well as the shot after Hagrid says, "We're a bit behind schedule, best be off." (00:12:55)
Visible crew/equipment: When Harry, Hermione and Ron reach the common room, on their way to the trap door, they're confronted by Neville, who asks, "You're sneaking out again, aren't you?" In the wide shot as Harry says, "Now Neville, listen...," Rupert Grint's (Ron) tape mark is visible at his feet. (01:53:35)
Continuity mistake: After shopping in Diagon Alley, when Harry confronts Hagrid about Voldemort, in the first overhead wide shot Hedwig's cage is right next to Hagrid on the bench and is positioned a particular way. Yet in the next shot, the cage is much farther from Hagrid and is positioned the opposite way on the bench. (00:28:45)
Continuity mistake: Harry speaks with Quirrell near the Mirror of Erised and the arrangement of the cloth in his turban differs in two shots than in the rest of the shots. First in the shot facing Harry as Quirrell says, "While everyone else was running about the dungeon, he went to the third floor to head me off," and then in the back shot just before Quirrell unwraps the turban, after Voldemort says, "I have strength enough for this." (02:08:05 - 02:09:45)
