After the car chucks out Harry and Ron, the car drives away and Ron and Harry chase after it. If you look closely you can see the shadow of someone driving the car.

When Harry curses Draco during their duel, Draco falls to the floor and his hair is messed up. When he gets back up his hair is slicked back again.

The entire Herbology class should have feinted at the sound of the Mandrakes. Seamus and Sprout have an entire conversation with them on.

When Harry pulls a tooth out of the Basilisk’s mouth, it's a straight tooth. The fang Harry uses to stab the diary, however, is a curved tooth.

In the Quidditch scene when Harry breaks his right arm, he leans on it for a moment to help himself sit up.

There are more than just two houses in one class. That's a book/movie difference, but Susan Bones somehow is in Gryffindor as well as being in the Gryffindor's classes. She's supposed to be Hufflepuff.

When Harry, Dumbledore, and Lucius Malfoy are in Dumbledore's office and Harry says he will be always be around to save the day, his face is clean. Later, when Harry gives Lucius the diary, his face is as dirty as it was when he was in the Chamber.

While the Anglia is getting beaten to a pulp by the Whomping Willow, Hedwig isn't moving at all.

During filming of CoS, Emma Watson broke her wrist. Several times during the movie you can see a little bit of her cast showing.

At the end of the movie with Lucius in Dumbledore's office, the sun reveals Jason Isaac's (Lucius') true short brown hair , underneath the blonde wig.

When Harry jumps onto his bed in the hospital wing after Dobby disappears again, it shows him jump on top of the covers. Less than a moment later, he has the covers over him. There is no way Harry can get under the covers in 3 seconds after landing on them.

How exactly does the Chamber open up to the night sky? Fawkes, instead of taking them up a slide, takes them past a rocky cliff, right towards the moon and stars. And either everyone is blind, or they just haven't really searched for the Chamber of Secrets? "Oh, that's just a cliff and a statue of Salazar, nothing to see here..." (see False Mistakes and Why)

The spell for belching slugs is "Eat slugs"? Ron doesn't do anything but say "Eat slugs", and five seconds later he's spitting them up.

Percy and Penelope sure do get around a lot. At the end, they're walking towards the Ravenclaw table and then they're walking past the Slytherin table.

Not only does Dobby block Platform Nine and Three-Quarters, but after impact and during a cut-scene, Hedwig's cage is closed, after being blown open from impact.

Harry didn't brush his teeth before he went to bed. It's clearly night time when they're pulled out of the chamber, and it's bright sunny afternoon daylight coming through the window to Dumbledore's office in the next scene, and Harry's still as dirty as ever. The famous Harry Potter is, afterall, too good to take a bath I suppose...

When the Snake-bordered door to the Chamber of Secrets opens, and all the way through Harry's approach to Ginny, he's carrying the wand in his left hand. Though, the wand when thrown down lands where his wand would have if it were in his right hand. Apparently Dan's right hand would have blocked the snake-door from the camera or something, so he was told to hold it in his left. His right hand is his wand hand, though.

When Hagrid enters the Great Hall, the next scene shows the doors closed. Then soon after they're open again when nobody came in.

As Harry chases Dobby into the hallway, he lands behind Dobby with knees bent and one hand stretched forward and the other back. The shot changes and focuses on Dobby. But when it returns to Harry, he is in a completely opposite stance to his previous one.

At Flourish and Blotts, Draco's neck is bare as he's coming down the stares. Later on, however, his neck is being covered up by a turtle neck of some sort.

Lockhart takes a few seconds to fall to the bottom of the Chamber of Secrets. Harry and Ron take much longer.

One, two, three, ferreverto. Too bad the words aren't written on the blackboard in back of McGonagall when she's teaching. Instead, very strange figures that are actually backwards, as the film reel was flipped over for better picture, are what's there. The same explanation could be used for the previous mistake with Harry's wand in his left hand.

When Harry is stabbing Tom Riddle's diary, the cut-scene where he closes the diary has his empty left hand closing it. In the scenes before and after, though, his left hand is raised and has the basilisk fang in it.