Other mistake: Before the battle of Helm's Deep, all of the Elves are positioned along the top of the wall. Their waists are right up against the shorter wall to protect them somewhat from incoming crossbow bolts. The Uruk-hai are heard arriving from a distance and Aragorn walks out a few feet in front of them to survey the battlefield. How could he walk out in front of them when they were positioned right up against the edge of the shorter wall?
Revealing mistake: When the camera moves into the "Seeing Stone" and pans up to reveal "the great eye," the entire tower was a miniature. It's not that noticeable, but what really makes it a mistake is the cotton balls used to make smoke on the smaller towers leading up to the big one. (It sticks out so obviously that one must ask, why did they CG the orcs at the bottom of the miniature, but use cotton balls for the smoke instead of CGing it?)
Revealing mistake: When Sam is running up the steps to stop Frodo from putting on the Ring in Osgiliath, you can see when he puts his right foot on the stair the "fake foot" toes slam into the stair and bend to a point which is impossible to achieve with a real foot.
Continuity mistake: When speaking of Merry and Pippin, a certain Orc says, "What about them? They're fresh." This Orc's face has very distinctive marbled skin coloring. After Grishnak says, "What about their legs? They don't need those..." when that other Orc says, "Just a mouthful," before Uglúk cuts off his head, the skin coloring on his face is quite different. (These were shot at different times.)
Audio problem: When Gimli says the line "Helms Deep! They flee to the mountains when they should stand and fight! Who will defend them if not their king?", Legolas, Aragorn, Gimli and Gandalf are walking towards the stables. Gimli's lips are not mouthing any of the lines. This is because it is the scale double of Gimli walking with the three other actors and John Rhys-Davies added the dialogue in ADR later.
Other mistake: When the refugees from Edoras are on the move to Helm's Deep, against the mountain range backdrop, they are going the wrong direction for a mountain range viewed from the north, where Rohan and camera are presumed to be. They should go from left (east) from Edoras to right (west) to Helm's Deep, but instead we see them going right to left, i.e. west to east. This occurs in two long-range wide-field shots.
Revealing mistake: In some shots you can tell that they used children or small people, for Frodo and Sam. Mostly, you can tell when they're shown from behind, in the company of tall men. You can also tell, from the slightly different hairstyles.
Revealing mistake: When Aragorn tracks Merry and Pippin near the beginning of the movie, after meeting Eomer, the trio stops at the border of Fangorn forest and you can see in this closeup that it's the scale double Brett portraying Gimli, not John Rhys-Davies.
Revealing mistake: In the aerial shot approaching the Horse Kings village the banners are flapping the wrong way and the chimney smoke is going into the chimney, instead of out, revealing that it was shown in reverse.
Suggested correction: Which scene is that? I couldn't find it anywhere.
It's the scene where Eowyn exits the door angrily and walks towards the fire circle thinking, in the trailer she's on the left of the screen but in the movie she's on the right.
Continuity mistake: At the battle of Helm's Deep, after the wall is breached we see the water flow out. Then there is an aerial shot of orcs entering the pool of water. It cuts to a closeup of Aragorn lying on the ground just in front of the pool, a very short distance from the orcs. He should have been visible in the aerial shot.
Visible crew/equipment: When the wounded Aragorn gets up on Brego the next shot shows him ride towards the sun, and his shadow behind him. The same thing goes for the camera crew's shadow. The shadow of the crew is seen at the very beginning of this shot. And there are no rocks beside the camera because the camera moves 180 degrees to show open terrain.
Revealing mistake: Gollum is leading Frodo and Sam through the Dead Marshes, towards Mordor. When Gollum runs across the first bit of the swamp, he treads into water; but the water does not move, nor does Gollum act like he has tread in water.
Revealing mistake: As Aragorn, Legolas and Gimli gear up for the battle of Helm's Deep in the Keep, Gimli puts on chainmail. After he says it's too tight in the chest, you see a back shot of Gimli standing facing Aragorn and Legolas. This man is obviously a scale double, as the body and posture are wrong.
Revealing mistake: When Theoden says, "They will break upon this fortress like water on rock," the camera is in a crane shot which slowly creeps up, becoming a medium close-up of Aragorn. As the camera flies over the front wall of Helm's Deep in the shot where Theoden delivers his line, look down into the deepest level of the castle towards the left of the screen. Rohan citizens are bustling and moving. If you watch closely, you can see the lowest level of the castle jump and shake in the shot. This is because that lowest level wasn't there in reality and it was added in the computer. (Probably can be seen only in the Widescreen version).
Continuity mistake: In the extended edition of The Two Towers, during the 'Elvish Rope' scene near the beginning, the mist disappears and reappears between shots. When Frodo falls and lands at the bottom of the ravine, there is lots of thick, white mist swirling around, but when it cuts to a wider shot, it has nearly all disappeared within a second. In the next close-up shot of Frodo, it has reappeared again.
Continuity mistake: When the Warg Riders attack the people of Rohan en route to Helm's Deep, Aragorn falls off his horse with his sword in hand and it remains in his hand, however it is suddenly sheathed he prepares to grab a charging Warg.
Audio problem: When Gollum starts leading the hobbits, just after they let him go, he slips slightly on one slope and there is a sound of stones sliding down. But no stones are dislodged.
Continuity mistake: When Gandalf, Legolas, Aragorn and Gimli step inside Meduseld (the scene where they arrive at Edoras in Rohan), as they are approaching Theoden the angle of Gandalf's staff changes. It appears from the shots taken at the front to be at an angle so that Wormtongue doesn't see he's still carrying it, but when cutting to the shots from behind the group his staff is almost vertical.
Continuity mistake: When Brego (Aragorn's horse) wakes up Aragorn by the river, after he had been thrown off the cliff, Brego is light brown. A few scenes later, Aragorn spots Saruman's army marching towards Helm's Deep, and in this shot Brego is all black.
Character mistake: When the Rohirrim are preparing for the Helm's Deep battle, a man is shown sharpening a sword on a grindstone. He is doing it wrong, but it is the way that most people think is the right way. The stone should be spinning so that the blade is "shaving" it, even though that seems like it would dull the edge.
