Revealing mistakes: The mechanism which makes the Quidditch box shake can be seen underneath the box when Wood falls over after catching the Bludger.
Miscellaneous: As the three children run across the field to Hagrid's hut, Harry says a few lines ending with "... why didn't I see it before?" Hermione is mouthing Harry's lines with him.
Crew or equipment visible: When Harry, Ron, and Hermione are struggling in the Devil's Snare, a puppeteer can be seen on the left of the screen, working at least some of the masses of tendrils.
Continuity: During the train journey, Ron's hair is parted in several different places.
Continuity: Harry's glasses sometimes have lenses, and sometimes don't, as do Dumbledore's.
Continuity: On the train, the same hill as well as lake (as seen by the waves in the middle of the water) are seen multiple times.
Audio/visual unsynchronized: Harry, Dudley and Uncle Vernon during the flying letters sequence.
Revealing mistakes: When Uncle Vernon is ripping up the letters that come through the mail slot, you can see that the envelopes had already been cut, making it easier for him to rip up.
Audio/visual unsynchronized: When Harry is going home on the Hogwarts Express he says "I'm not going home, not really". The next view of the camera shows that Harry is still saying "not really" but you can't hear the words
Continuity: When Harry, Ron and Hermione are talking to Hagrid about Fluffy, Ron's scarf goes from being on his shoulder to being draped over his shoulder.
Continuity: Harry's scar clearly changes positions throughout the movie.
Miscellaneous: When Harry receives countless acceptance letters from Hogwarts, he fights with Uncle Vernon, saying the dialogue "They're my letters! Let go of me!" Harry's voice is far deeper than the Harry in the rest of the movie, indicating this line was re-dubbed long after main production when Daniel Radcliffe's voice had already begun to change. (Also, his lips are not moving when he says those lines.)
Miscellaneous: When Harry receives his first letter, Uncle Vernon says "Yours? Who'd be writing to you?", Dudley is standing next to him and is seen mouthing Uncle Vernon's lines.
Continuity: When Hermione runs across the field her bag switches arms.
Revealing mistakes: When Dumbledore is awarding Neville 10 points, you can see the plastic used to make Neville's ears stick out when he turns toward Harry.
Continuity: When Harry wakes up in the beginning of the movie his shirt is tucked in the back of is trousers. In the next shot it is not.
Revealing mistakes: In the scene with the flying keys, we can see the string holding up the broomstick just before Harry grabs it.
Continuity: When Harry goes looking for a book on Nicolas Flamel in the restricted section he opens up the screaming book to the first page. When the book starts to scream he is in the middle of the book.
Crew or equipment visible: When Harry, Ron and Hermione just left Fluffy for the first time and walk into their dorm area, we see, under the painting, the feet of someone closing the painting.
Continuity: The note that Hagrid gives to the teller in the bank is wrinkled in one shot, neat and clean in the next, and then back to wrinkled.
Continuity: In Diagon Alley, Harry and Hagrid walk past the same cart and storefront three times. In the opening wide shot, they walk past the purple storefront with the yellow moving scissors and the cart of market goods in front of it. Three shots later, the storefront and cart are shown again in detail, as Harry and Hagrid pass. The next shot shows them passing the cart (with a stack of cauldrons in the background). Several shots later, after passing the store with the owls, they are seen once again passing the cart with the same stack of cauldrons in the background.
Continuity: Just after passing Madam Malkin's shop and before the owl emporium in Diagon Alley, a woman dressed all in black and a man with a burgandy top hat and mutton chops pass on Harry's right walking in the opposite direction. In the next shot, as Harry looks to his left, the same pair can be seen standing and chatting in the doorway of the owl emporium.
Continuity: In Diagon Alley, Harry and Hagrid pass many groups of people multiple times, though they appear to be walking continuously in one direction. Watch for the wizard with curly red hair, the man with a top hat and mutton chops, and the group of three girls who cross in the foreground of the opening shot.
Continuity: When Ron gets drooled on by Fluffy and gets wet, but two shots later he's completely dry.
Errors in geography: When Harry arrives at Hogwarts, Professor McGonagall announces that the Sorting Ceremony will begin "momentarily". In UK English, momentarily means "for a moment" (i.e. briefly), and a Scottish witch as pedantic and precise as McGonagall would never use the American meaning of the word ("in a moment" or "soon"), even though the American meaning might be well understood. Then again, given that the otherwise equally pedantic Snape says "less" when he means "fewer", it could just be that the teaching staff's use of English is just as sloppy as it is in schools all over the muggle world.
Continuity: When the first years climb the stairs and meet Professor McGonagall for the first time, Ron's robe is hanging partly open in one shot, but is closed in the next.
Audio/visual unsynchronized: When Harry and Ron are fighting the troll in the girl's toilet, they use a spell to lift the troll's club over its head and drop it. The club does hit the troll and makes an appropriate sound effect, but then the club falls to the floor, it makes no sound at all.
Incorrectly regarded as goofs: Many viewers believe that the infant Harry in the flashback is wearing anachronistic Blue's Clues pajamas. The design on the sleeve is actually a rabbit.
Crew or equipment visible: During the chess scene, the shadow of a figure can be seen covering a light shining on the chess board near the bottom of the screen.
Continuity: When Harry, wearing his Invisibility Cloak, spies on Professor Quirrell being bullied by Professor Snape, the shots filmed from Harry's point of view have him at eye level with the adults even though he is clearly shorter than they are.
Continuity: In the scene in the hut on the rock, where Hagrid comes to fetch Harry, Harry's T-shirt is hanging off his left shoulder at the beginning of the scene, and then it is in the center of his chest, then hanging off the left again, and then back to center.
Audio/visual unsynchronized: In the scene following the defeat of the troll, Quirrel is shown speaking with the other professors, at which point they, and the trio, leave the girls' bathroom. Their footsteps are clearly heard as they move down the hall; however, in the next shot of the troll laying on the floor, the sound effects have ceased. In the last shot, of Quirrell jumping nervously in response to the troll grunting, the footsteps can again be heard.
Continuity: When Mr. Dursley is talking about how there's no post on Sundays and the first letter shoots out of the fireplace, the log poker is in the middle of the hearth, when all the other letters come shooting out, the poker is on the right side.
Miscellaneous: When Filch enters the Restricted Section of the library in search of the disturbance, he passes Harry, who's hiding under the Invisibility Cloak. The camera angle leads the viewer to believe Harry is as tall or taller than Filch. Harry should be a foot or two shorter.
Continuity: When the troll attacks Hermione the first time, its club demolishes the first three stalls. Right before the troll swings its club again, the door of the second stall is still standing.
Factual errors: According to the book, Hogwarts students reach the train by going through platform no. 9¾, which is secretly located in the barrier between platforms 9 and 10. In reality, platforms 9 and 10 are in separate buildings, and there is no barrier between them, but railway tracks. People wrote to Rowling about this, and she admitted getting confused between King's Cross and Euston stations. The Platforms actually used in filming are platforms 4 and 5.
Continuity: During the first meeting of Harry, Ron and Hermione on the Hogwarts Express, Hermione's tie changes from being crooked to one side, to straight then back to crooked again
Revealing mistakes: When Harry and Hagrid are in the Bank at Diagon Alley. Hagrid gives the goblin a card. Multiple time through camera shots the cards corners have been bent and smoothed.
Crew or equipment visible: When Harry takes Ron to the Mirror of Erised, when Harry drops his cloak and runs away, you can clearly see the lime green from the outside.
Continuity: Dudley eats Harry's birthday cake with his hands, but when he turns around, after Hagrid has given him a pig tail, there is no cake or icing on his hands or face.
Miscellaneous: When Harry, Ron, and Hermione are walking up the stairs and the stairs are changing, you can still see the banister wobbling back and forth even after they've reached their final position.
Revealing mistakes: During the chess scene when the chess pieces are being destroyed, the bits of rubble can be seen flying in opposite directions and sometimes even just a split second before the actual piece is destroyed.
Crew or equipment visible: At Kings Cross the camera crew is reflected on the side of the train on the right.
Continuity: After Harry gets sorted into Gryffindor he goes and sits down next to Ron with Hermione across from him who is sitting next to Percy. In the next shot when Harry asks who's that teacher next to Professor Quirrell he asks Percy and Hermione is sitting to the right of him and Ron is across from him.
Continuity: After Harry has received his wand in Ollivander's, his hair is parted to show his scar. However, when Hagrid knocks on the window and Harry sees Hedwig, his scar has mysteriously disappeared.
Revealing mistakes: When the multiple letters fly into the house from the fireplace, Harry catches one out of the air and it is obviously a single sheet of paper rather than a stiff envelope like the first one that was delivered and opened.
Continuity: When Harry is in the restricted section, he sets down the lamp to his left before taking off his invisibility cloak, setting the cloak to his right. When Filch's voice is heard and Harry grabs the cloak, the lamp is on top of the cloak and thus falls onto the floor.
Revealing mistakes: When Aunt Petunia is cracking the eggs and finding they are filled with letters rather than yolks, the envelopes are clearly a thin sheet of paper, not a thick envelope with a letter inside. (You can tell they are envelopes because you can see one is addressed the same as the previous envelopes)
Miscellaneous: When Harry is quoting the article about Gringotts being broken into, he reads "... the vault in question; number 713...” however if you look closely at the article shown, it does not mention the vault number. Everything else about his quote is accurate, however.
Revealing mistakes: In the very beginning of the movie, Dumbledore is walking towards McGonagall who is still in cat form. As he is walking, you can see his shadow cast against a backdrop of trees.
Continuity: When Harry is upside down with the troll holding him by his legs, his hair is pointing to the floor and his scar is no where to be seen on his forehead.
Miscellaneous: In the scene where the owls are dropping the gifts, a girl near the top left corner misses it and it hits the floor.
Continuity: In Gringotts, when Hagrid showed the letter from Dumbledore, it was wrinkled at the ends. But when the goblin held it, the wrinkles were gone.
Revealing mistakes: At the end of the chess match, Ron is supposedly knocked unconscious. When Harry and Hermione run to check on him, Harry touches Ron's arm and Ron's mouth twitches.
Continuity: In the scene where Harry and the Dursleys are getting into the car before going to the zoo, Vernon is seen speaking to Harry. From the backside, Harry's button up plaid shirt is seen on his shoulder, then from the front it is hanging off his shoulder.
Revealing mistakes: During the Quidditch match after Hermoine looks at Snape through the binoculars and says "It's Snape! He's jinxing the broom!" You can see Ron mouthing her lines along with her.
Continuity: At the beginning of the movie, when Harry Potter is dropped on the doorstep of the Dudleys (after his parents' death), he is clearly an infant. However, in the album that Hagrid gave Harry at the end of the movie, there is a picture of Harry as a toddler with his parents. If at the beginning of the movie he was an infant when he was orphaned, then it is not possible for him to have a picture with his parents when he was a toddler.
Continuity: After Ron uses the levitation spell to knock out the troll with its own club, we neither hear the club hit the floor, nor do we see it afterwards.
Plot holes: After the Diagon Alley scene Harry and Hagrid go and get some supper, after which we see Harry and Hagrid at the train station. Harry is going to get on the train and Hagrid says he has to get going so that he can get the package back to Dumbeldore. Since we all know that Harry's birthday is at the end of July / beginning of August then wouldn't Harry have had a whole other month to wait until he had to go on the Hogwarts Express? Hagrid not having yet delivered the package implies he waited around for a month rather than going to Hogwarts and then coming back for Harry.
Revealing mistakes: After the final fight when Harry is lying unconscious his hair is thrown back revealing his scar. It has clearly been drawn on with a marker and looks much less real than the wounds on his cheek.
Crew or equipment visible: During the final chess scene when the Queen is about to attack the knight on which Ron is sitting and later when Ron falls, in both occasions we can see a body double (stuntman) used for Ron, siting on the horse for the attack and during the fall.
Continuity: After Harry lets go of the snitch Wood looks around, as if he can't see it then, looks the other direction completely, when the snitch has clearly barely moved from in front of Harry.
Revealing mistakes: When Harry's uncle chases after him when the letters are coming into the house, you can clearly see a crack in the wood covering the mail slot just before the letters burst through.
Revealing mistakes: In the scene where Hagrid breaks into the Dursleys' house on an island in the middle of the ocean during a huge storm, the shot where Hagrid bends the end of Vernon Dursley's shotgun, you can see the white marker where the prop shotgun is supposed to be bent.
Crew or equipment visible: In the scene in the hut on the rock when the Dursleys panic after Hagrid grows Dudley a tail, you can see plainly Hagrid's tall body double. The same can be noticed in The Leaky Cauldron when Hagrid enters the building.
Revealing mistakes: During the scene in the reptile house in the zoo, the snake, a Burmese Python, not a magical creature, is blinking. Snakes cannot blink because they have no eyelids. Instead of eyelids they have transparent scales over their eyes.
Continuity: At the end of the oversize chess game when Harry says "Checkmate," the king drops the sword which is resting the point on the chess board. When the king drops the sword, it falls, swiveling on the grounded point yet in the final angle, the entire sword is parallel to and about a foot above the the ground, falling and landing flat.
Revealing mistakes: When Harry, Ron and Hermione first enter Fluffy's corridor, and start running towards the door, one of the torches clearly has a little flame, before it 'bursts' into flame when they pass it.
Continuity: In the scene where Harry is writing down what Snape is saying, the writing is clearly different in the close up shot, than every other time we see the paper, it is much larger and messier whereas in the close up it is small and neat.
Continuity: When Hermione falls through the trap door guarded by Fluffy, she wears white tights under her skirts. These tights are gone during the Chess game.
Revealing mistakes: Owls are very quiet in flight. They have to be, they are hunters and rely on being able approach their prey silently and hear where that prey is in the first place. The owls in Harry Potter - especially in the scene where hundreds of them gather outside the Dursley's house in Privet Drive - are very loud. Every time they appear, the soundtrack contains loud flapping noises which sounds more like some sort of pigeon than any owl.