Revealing mistake: Right at the start when Harry is on his bed and making a light under his sheet, you can see that he is actually on something like a light panel in order for this effect to happen. For one thing, when he moves around on it, it doesn't bend like a mattress does. Also, about halfway down the bed you can just see where the sheet ends and this panel begins. (00:00:50)
Revealing mistake: Watch as Hedwig lands on Harry's arm. It's quite obvious he has some protection under the shirt sleeve as his arm and wrist is unnaturally thick. (00:14:00)
Revealing mistake: When Harry first opens the Monster Book of Monsters, when looking closely, you can see the hollow part of the book that spits out the paper. Easiest to see when Harry is looking under the bed. (00:15:40)
Revealing mistake: When Neville opens his 'Monster Book of Monsters' he falls to the ground. Then he is lying on the ground and his book is attacking him again. We can see the pieces of pre-cut papers, that should be coming out of the book's mouth, actually come up from the ground, when Neville is holding the book above him. Obviously it's not real. (00:31:15)
Revealing mistake: At Hagrid's lesson, just after Malfoy wound Harry up, there is a close up on the class when they first see Buckbeak and you can see Emma Watson holding back a laugh. Surely if her friend was being picked on it wouldn't be funny, plus they're supposed to be scared of Buckbeak. (00:32:05)
Suggested correction: Not true. I saw this scene several times and I never saw Hermione holding back a laugh.
Revealing mistake: As Harry and Buckbeak fly over the loch, Buckbeak's foot trailing in the water leaves a wake, as it should. This wake should also disturb the ripples and waves that are already present on the surface of the water, but they do not. It is obvious that the wake effect was added in, but the foundation shot of the loch was not edited to help it make sense. (00:35:20)
Revealing mistake: After Harry's first ride on Buckbeak during Hagrid's class, before Buckbeak cuts Malfoy's arm with his talon, when Malfoy holds his arm over his face, the pre-cut and ripped sleeve is visible in this close-up. (00:37:55)
Revealing mistake: When they look at the newspaper about Sirius being sighted you can see the picture of Sirius on the newspaper doesn't move at all. (00:37:55)
Revealing mistake: During the DADA class, as the Boggart balloon flies by, Lupin's eye contact with the balloon, as well as others', are not quite in sync as they follow the balloon with their eyes. (00:44:15)
Revealing mistake: During the DADA lesson with the Boggart, the body double for David Thewlis (Lupin) is quite evident in some close range, head on and side shots. As a matter of fact, Emma Watson's and other actors' body doubles are very noticeable in many shots not involving a stunt. (00:44:15)
Revealing mistake: In the scene in which Harry, under the guise of the Invisibility Cloak, is dragged by the Weasley twins into the castle by his arms, it's obvious that the twins are miming a person in between them. There is one point when they round the corner right before throwing him onto the stairs, the twins are pretty much side by side, there is absolutely no room between them for a person at that point. They then widen the space again right after they round the corner. (00:56:55)
Revealing mistake: When Malfoy and his friends are messed with by an invisible Harry, Malfoy is dragged along by Harry. In the SECOND shot, when Malfoy is dragged along (which is a closeup shot of Malfoy's legs up in the air) pay attention to the bottom right corner of the screen, and you can see a bare hand quickly move into view, quite close to the screen. This can't be Malfoy's hand because he has gloves on. Slo-mo is not necessary to see this. (01:00:15)
Revealing mistake: When Ron and Hermione are arguing with Malfoy near the Shrieking Shack, Malfoy visibly flinches before he is hit by the first snowball. He's not looking in the right direction to see it coming. (01:02:15)
Revealing mistake: In the scene at night, when Harry is in the hallway with the map, the tip of his wand lights up. And later in that same scene, when Snape has the conversation with Lupin and Harry, Snape's wand does the same. However, if you look closely at the shadows on their faces, they're being lit from above, not from the wands' light below them. (01:13:45)
Revealing mistake: When Hermione fakes reading the crystal ball, Trelawney insults her and Hermione knocks the crystal ball off the table. As the crystal ball leaves its stand it turns over and the tube used to create the smoke effect inside the ball is visible. Then as the ball rolls toward the stairs, there are no tubes visible. (01:19:55)
Revealing mistake: After Ron has been dragged down the hole by the Grim, you see both Harry and Hermione get hit by The Whomping Willow and they fly backwards and land on the ground. Notice when Harry places his left arm in the ground, the ground is unnaturally soft. (01:25:00)
Revealing mistake: While he sits by the Whomping Willow, Ron shouts, "Harry, Hermione, run! It's the Grim!" When Sirius the dog runs toward them, in the shot facing Harry and Hermione, their eyes are not quite in sync with the dog before it leaps. (01:28:00)
Revealing mistake: While being hurled around by the Whomping Willow, Hermione grabs hold of Harry's shirt in the close-up. In the next shot as Harry's being lifted up, the bottom of the left side of his blue tee shirt is pinned to his pants, also visible in another shot. (01:29:30)
Revealing mistake: In the Shrieking Shack, when Harry sends Snape flying into the bed, the canopy collapses in the stunt. In this shot the metal bars at the top of the canopy frame are visible, whereas in the following shots it is no longer there. The way the canopy frame actually hangs after stunt differs considerably and the draperies hanging on the bed differ in the shots prior, during and after the stunt. (01:33:55)
Revealing mistake: At the Shrieking Shack, when Harry shouts, "Expelliarmus!" there is a nice close-up of Snape and it is obviously not Alan Rickman flying backwards onto the bed. (01:34:00)
