Deliberate mistake: In the scene after the Helm's Deep battle, when Aragorn meets Eowyn, the earlier footage of Aragorn's return to Helm's Deep is used. He has the wound on his shoulder and is dressed like he was during the 'falling' episode. The background (people in the fortress walking calmly) also indicates that this takes place before the battle. This scene should immediately follow the one where Aragorn is greeted by Gimli ("you are the most reckless man I ever knew"). Confirmed on cast commentary, extended DVD.
Deliberate mistake: In the director's commentary, it is explained that the scene of Aragorn arriving at Helm's Deep was filmed early in the shoot, before it was decided that he would have lost the Evenstar. Consequently it had to be painted out. However, when Aragorn turns to leave Gimli a flash of silver from the jewel at his chest still remains.
Deliberate mistake: During the Warg attack, Aragorn jumps onto a moving Warg and in a close-up, he headbutts the Orc rider. In the next shot, as they're riding, they pass a Rohan rider on a white horse. In the background there are dead bodies strewn on the hill to their right, as they're approaching a huge bush also to their right. As they continue moving, there are multiple shots, including Aragorn falling and stabbing the Orc. In the shot just after the Orc rips off the Evenstar, the Orc falls off the Warg and it is the very same background plate as before, as they pass that huge bush to their right. These two pieces of footage were obviously one sequence that was split and other shots were inserted in between them.
Deliberate mistake: Just after they've clashed with the Warg, while riding on Arod, Legolas lets loose his first arrow and hits a Warg in his face and it flips over. In this first shot, the background behind this Warg is the same background as in the very next shot. This first background shot is really the successive shot of this second background shot. The shot just after Gimli falls off his horse, is the third successive shot, only it's been flipped. The same men on horses are riding across the field in the background, as this was one piece of footage that was cut into three parts. Warg and riders were added to the image, to make them appear different and one was flipped.
Deliberate mistake: During the Warg battle, the fourth shot after the close-up of Legolas letting loose the arrow while riding on Arod, a Warg and rider attack a Rohan. In the background is a particular hillside with some dead bodies, and on the left of the screen lies a dead horse with an arrow in its rear. The very next shot, a horse and rider fall and a Warg attacks the rider. The background hillside in this shot, dead horse and all, is the same background plate as the previous one, only it's been flipped.
Deliberate mistake: On the Wall of the Hornburg, in the close-up of Aragorn, he dramatically draws his sword with his left gloved hand. In the next close-up of Aragorn, when he yells, "Hold!" he raises his left hand with the ring on his index finger. In editing, they wanted to have the Elves on the left of the screen and Uruk-hai on the right, so they flipped the first shot.
Deliberate mistake: During the Warg attack, Aragorn is being dragged by the Warg and is heading for the cliff. In the very last wide shot of Aragorn, from behind his head, we see the hillside and riders behind the Warg, where they just came from. Next, we see a couple of shots of Gimli finishing off a Warg. In the next wide shot, the hillside including riders and bodies is the same one as earlier, only it's been flipped.
Deliberate mistake: First there's a shot of Saruman as he communicates with Sauron using the palantir, then a shot of Barad-dur. Next we see the Orcs at Orthanc pulling down trees and a shot of a tree falling into the cavern below. In FotR, just after Gandalf catches the moth atop Orthanc, we see a shot of a tree falling into the cavern down below. These are the exact same shot, only it's been flipped in this movie.
Deliberate mistake: In two scenes in particular, Legolas is letting loose his arrow with his left hand, because of shot flipping. When he kills the Warg approaching Gimli and when Legolas severs the rope, causing the tall ladder to collapse. The ladder shots of Legolas were put together later during editing, because Peter J. wanted an extra 'hero' shot of Legolas at Helm's Deep. They took the same shots of Legolas trying to take out the Berserker Uruk-hai and flipped it to specifically fit the later scene of the ladders going up. Commentary, extended DVD.
01:08:55 - 01:17:30Super Grover
Deliberate mistake: In the first close-up shot of the scene, Aragorn is walking and talking to 'Legolas'. Legolas' back is shown, as Aragorn is speaking to him. At a certain point, 'Legolas' turns his head to his left and in this close-up it is very clear that it is not Orlando Bloom, but his body double, Morgan. Extended DVD.
Deliberate mistake: When Faramir is about to release Frodo and Sam, not only are the Elven brooches the wrong way round, as someone else has noted, but the whole scene is flipped. You can tell because the leather straps that hold their baggage are the wrong way round as well. Faramir's shots go from normal to flipped a few times, when he walks over, kneels and then rises.
Deliberate mistake: Legolas leaps onto Arod and as he rides, both of his hands are clean. After they've just clashed into the Warg riders, in the close-up of Legolas as he releases his arrow there are dark smudges visible on Legolas' fingers and knuckles on his right hand. In the close-up of Legolas as he lets loose the arrow into the Warg that is about to attack Gimli, we see both of his hands are smudge free. This shot is flipped, so the right hand that was previously smudged is now the left hand, which is clean anyway.
Deliberate mistake: At Helm's Deep, Theoden says, "I want every man and strong lad..." behind them is Gimli, who has a conspicuously reddish face, and his beard is split down the middle into two braids. Éowyn confronts Aragorn, she apologizes and hurries off, walking between Legolas and Gimli, who looks the same as in the earlier shot. It's obviously Brett (scale double) in both shots, the beard with its two thin braids are completely different when next we see Gimli, in a close-up at the armory. This time the beard is full, with hair between the two very thick braids, and his face is a normal color.
00:51:50 - 00:52:55Super Grover
Deliberate mistake: During Theoden's attack, Arwen on a white horse is visible in about 3 frames. It was confirmed on the Commentary that Arwen took part in the Helm's Deep scenes as originally filmed, but was cut from them later, but apparently not completely, because she is seen in a number of shots. During the beginning of the attack, when the riders are still in the fortress, several shots end abruptly when only the white horse (different from Arod, its head is not covered with protection) is visible and not the rider. She is also seen riding down the causeway, in front of Legolas. Her hair was colored blonde, her body and clothing were shaded and colored green, to disguise her.
Deliberate 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.