Continuity mistake: In the opening aerial shot of the playground, the landscape surrounding it is flat, devoid of any shrubbery, and there are no buildings or streets nearby. In the close-up shots with Harry and Dudley that are shown from various angles, there are now houses, small hilly mounds, bushes, and a road in the background. (00:00:50)
Continuity mistake: At the playground, when Harry sits on the swing his long shadow is cast directly in front of him as he watches a boy and his mother by the round-a-bout, which is also directly in front of him. Problem is their shadows, which are considerably shorter than Harry's, are cast to Harry's left. (00:01:05)
Continuity mistake: At the playground, when Dudley and Harry have a confrontation, Dudley wears black shorts with large white designs of words and numbers. When Dudley and Harry enter the tunnel and then later, when yumpy Dudley is in his house, Dudley's shorts have completely different designs (though it is the same type of shorts). (00:01:30 - 00:03:00)
Continuity mistake: At the very start, Harry has his wand to Dudley. In this shot he is right by Dudley. When it goes dark, Harry and Dudley have moved apart a fair bit. (00:02:10)
Continuity mistake: When Harry and Dudley reach the tunnel (out of the rain) Harry stands level with the "r" and "k" in the very large graffitied word "Stark", and Dudley is well past the large white graffiti to his right (viewer's left). The next shot, from the boys' POV, the empty tunnel is shown and on the left is the gratified word "Stark" and part of the white graffiti on the left, even though the two boys were actually just standing quite a bit farther into that tunnel. (00:03:00)
Continuity mistake: When the Dementor grabs Harry at the start, Harry's feet are apart. Camera does a quick cut and now one foot is tucked behind the other. (00:03:15)
Continuity mistake: When Harry and Dudley enter the tunnel, to Harry's left is the large graffitied name "Stark" and to Dudley's right is the graffitied name "Jim", which is directly opposite the "ta" in "Stark". When the Dementor holds Harry up by the throat Harry hangs well past "Stark", as the Dementor floats at an angle in front of "Stark". After the close-up of Harry's sneakers, in the wideshot, Dudley's silhouette (at the right, in the foreground) is off to Harry's left (viewer's right) staring to his left (precisely where Harry and the Dementor are positioned), which would put Dudley farther into the tunnel. But when it cuts to facing Dudley close-up, he's now standing in front of the "Jim" graffiti, which is off to Harry's right, closer to the entrance and he's still staring off to his left. (00:03:20)
Continuity mistake: When the Dementors attack, Harry's wand falls. It changes position from the first shot; just note the cracks on the ground. (00:03:50)
Continuity mistake: When the Dementor lifts Harry off the ground in the tunnel, Harry's feet dangle beside the very large graffitied word "Stark", and then falls to the ground past the word with his feet near the "k". After it cuts to the closeup of his wand, Harry is now lying beside the "S", even closer to the Dementor, though he is trying to back away from it and reach his wand behind him. (00:03:55)
Continuity mistake: When Harry shouts, "Expecto Patronum," he points his wand at 'his' Dementor as the Patronus repels it and it flees. Harry then stands and puts his wand arm down, but in the next shot his wand is still up, pointing to his right with the Patronus in mid-air. (00:04:00)
Continuity mistake: Before the Dementor attack, just as the sky darkens and the wind kicks in at the playground, newspaper is blown against the fence, behind Harry, but after a brief shot of Dudley the newspaper is gone then blows there again. In the following overhead shot, the newspaper is gone, but when it cuts back to Harry, the newspaper is back yet again. (00:04:00)
Factual error: After returning to the Dursley's after the dementor attack It is dark, this shows again when Vernon puts Dudley in the car. However, the howler from Mathila Hopkirk says that at 6:23pm Harry performed illegal magic. As the side story shows it is a hot summer, it wouldn't get dark until way past 8pm. (00:04:53 - 00:07:20)
Suggested correction: Fairly certain the film was clear that the reason it got dark was because of the dementors, they have the ability to change the weather to depressive darkness.
Continuity mistake: When Dudley and Harry enter the living room after the Dementor attack, Dudley has his arm round Harry in the long shot from Petunia's chair. However, in the closeup of the door after the instant camera cut, his arm is now down by his side. (00:05:20)
Continuity mistake: When Harry has brought Dudley home, as Uncle Vernon is telling Harry that he's finally driven Dudley insane, Dudley's expression changes between shots from crazy to normal. Aunt Petunia's arm also changes position around Dudley. (00:05:50)
Continuity mistake: At the Dursleys, when the owl delivers Mafalda Hopkirk's letter and it announces Harry's expulsion from Hogwarts, the fan on the counter noticeably changes its position. (00:06:00)
Continuity mistake: When the Dursleys leave in their car, there is a large hanging plant to the right of the front door with mostly large white flowers and some red. When Harry, Moody, Tonks and the rest leave the house, the flowers are now small and red. (00:06:50 - 00:08:40)
Continuity mistake: After being expelled, when Harry places the photograph on his desk, his wand moves closer and then farther away between shots. (00:07:15)
Continuity mistake: While still at the Dursley's, Harry has a dream and wakes up. When he wakes up there is moonlight shining on his pillow, right near his face. When the camera angle changes, the moonlight on the bed where his face is is gone. (00:07:50)
Visible crew/equipment: When Harry is walking out of the Dursley's house with Moody and the others, as they walk across the front of the house, just after Kingsley says, "Dumbledore has persuaded the minister to," on the left-hand side ground floor window the reflection of the moving reflector screen is visible. (00:08:40)
Continuity mistake: When the Order get the brooms at the start, the height they are being held at, changes during an instant cut. Harry and Kingsley's are most noticeable. (00:09:05)
