Continuity mistake: Frodo, Sam and Gollum are resting in the middle of the Dead Marshes. In the wide shot, Sam gives Frodo some Lembas and takes a piece for himself. Sam breaks his apart and smells it a couple of times, while looking at Gollum he holds the Lembas away from his face. Next there's a close-up of Sam holding the Lembas right near his mouth. The piece of Lembas is much bigger in this close-up, than in the very next shot, showing Frodo and Sam.
Audio problem: First there is a wide shot of the Dead Marshes and Gollum says, "Soft and quick as shadows we must be." Then in the next shot as the camera starts to pan towards Sam, he begins to say, "I hate this place, it's too quiet..." When the camera first shows Sam, his mouth is not in sync with these particular words, "I hate this place," the words originally said on camera were changed during ADR. Extended DVD.
Continuity mistake: After seeing the Mûmakil, Frodo and Sam are captured by Faramir's men. In the close-up shot as Frodo says, "We are bound to an errand of secrecy..." he's being held by one of Faramir's men around the shoulders and Frodo is holding the man's forearm. A second man is close to Frodo's left whose right hand is down. In the very next wide shot Frodo is holding the man's arm differently and the second man to his left is not only further away, he's standing differently and grasping the hilt of his sword in front of him. In the next two close-ups of Frodo, he's holding the man's arm exactly the way he was in the first close-up. It's also obvious in the wide shot that it's the scale double of Frodo.
Continuity mistake: At the beginning of the scene, Sam is cooking the rabbits. Behind Gollum, Frodo's coat and pack lay on the left side of the overturned stone carving. In the following close-up, when Frodo goes over to his pack to take out plates and spoons, his coat is now on the right of the overturned carving. In the next wide shot, it's on the left again.
Continuity mistake: When the Uruk-hai are sending the three huge ladders up on to the Keep, watch the last one just before Legolas cuts the rope that is pulling it up. The ladder has just passed the 90 degree/vertical point. Naturally, after that it starts gaining speed as it falls. Then it cuts to Legolas, who waits a second or two before firing his arrow. That would be plenty of time for the ladder to pass the point of no return, and hit the wall, so it would not have mattered if Legolas had shot it or not it would still have reached the Keep.
Revealing mistake: Just as Theoden yells, "They have broken through, the castle is breached." Legolas is first seen on the exterior wall pulling the string of his bow with NO arrow in his hand twice, but the other times he pulls the string on the bow we do see the arrow before reaching the bridge. Also, after he crosses the bridge, before he gets to the stairs, when he reaches behind him for an arrow the arrow is on his back, not in the quiver, it's just simply on his back. (Do slo-mo or frame by frame if necessary).
Continuity mistake: While running in Fangorn Forest, Aragorn stops kneels down and then says, "These are strange tracks." In the wide shot preceeding just as he kneels down, and in the close-up when he says those words, his position and the position of the rocks and trees surrounding him are very different in both shots. This has nothing to do with camera angle.
Continuity mistake: At Henneth Annun, Frodo and Sam have their blindfolds removed, and to their left are two barrels. In the 1st shot, one barrel has a brown cloth draped on it with a bowl of nuts and cracked shells and on the second barrel, candles that are not lit. In the 2nd shot, Faramir walks in and to his right the brown cloth under the bowl of nuts is draped differently, the candles, which are lit now, are a different variety and there are also ceramic jugs near the barrels now. After Frodo answers, "Yes. For my part," Faramir gets up and as he walks, the items on the barrels look the same as in the first shot.
Revealing mistake: As the Uruk-hai are slamming into the chamber door, with the battering ram, Gimli and Legolas are standing at the door. Across the room, Aragorn says, "Ride out with me," then in the next three shots of Theoden, he's standing in front of the same wall, with particular markings. In the very next shot, Gimli says, "The sun is rising," and he's standing right in front of the very same wall that Theoden is standing right in front of. Then, in the next shot, still standing at that wall, Theoden says, "Yes. Yes. The Horn of Helm Hammerhand..." Both Theoden and Gimli, can not be in front of the same wall at the same time. In the next shot of Gimli, still standing at that same wall, responds, "Yes." He then starts to go off to blow the Horn. The next shot, is a close-up of the door - all the men in front of it and some wood are knocked away, due to the force of the battering ram. In the next shot, as Theoden says, "Let this be the hour when we draw swords..." between Aragorn and Theoden, the men are seen huddled together at the door again, and Legolas and Gimli are there too. Yet, in the next shot, Gimli is hurriedly running up the steps of the tower to the Horn.
Continuity mistake: Aragorn, Legolas, Gimli, Theoden and others are in the Keep after the walls have been breached, while Aragorn is talking to Theoden about riding out together and the like, Legolas and Gimli are tipping tables up and putting them against the door. However, in one shot when Aragorn is asking about a passage to get the women and children out look behind him, Legolas and Gimli are standing with their weapons drawn, then in the next shot they're back to tipping tables up.
Continuity mistake: After the shot of Gandalf, Aragorn, Legolas and Gimli riding towards Edoras, there's a close-up of Theodred. In this shot there is a red pillow next to Theodred's face on his right. In the wide shot behind Éowyn, there is no red pillow to the right of his face. Though there is in this shot a white pillow corner leaning on the headboard, that is not in the previous front wide shot. The fur cover at the foot of the bed lies differently in the front and back wide shots too.
Continuity mistake: At Edoras, as Wormtongue sits on Theodred's bed speaking to Éowyn, she says, "Leave me alone, snake!" As she stands we see Wormtongue's back, and the fur covers draped over Theodred's legs and all around the foot of the bed. In the next close-up of Wormtongue, he says, "Oh but you are alone," we see Theodred's legs slanted and no fur cover, just the white cover. Cut away to a shot of Éowyn, then back to Wormtongue, and the white cover on Theodred is lying differently on him and some of the fur cover is now seen. Wormtongue did not change positions between shots.
Continuity mistake: In the stable at Edoras, Éowyn gives the saddle to someone, then starts to walk towards Aragorn, and her long hair is spread out all around her shoulders. Cut to the close-up shot, and her hair is now parted at the neck, hanging straight down in front and back. When Aragorn walks away, her hair is all around her shoulders again.
Revealing mistake: After Haldir dies, Aragorn jumps onto the only ladder resting against the steps 'inside' the Deeping Wall. Hanging onto the ladder, he then falls on top of the Uruk-hai down below. The ladder is now lying on the ground perpendicular to the steps of the wall. However, when Aragorn runs up the stone steps on the side of the Keep, in the aerial CG shot of the wall below, the ladder is not lying on the ground where it should be, under the scurrying feet of the Uruk-hai.
Continuity mistake: In this first shot, there is a close-up of Legolas releasing an arrow towards the oncoming massive Warg attack. Then a wide shot of the hill, with Legolas still letting loose, and in the background, the riders on horseback coming over the hill. To Legolas' left are two riders on horseback that are just passing him. They are Gamling and Gimli. But in the next shot, Gimli is just coming from behind Legolas, and then Legolas leaps onto Arod.