Revealing mistake: When the riders break out of Helm's Deep, you can see the hooves on some of the horses pass straight through the Uruk-hai corpses on the bridge. (01:29:10)
Revealing mistake: Shadowfax, the horse that only Gandalf is supposed to be able to ride, will not take a saddle and bridle, so throughout the majority of the film, they try very hard to hide the saddle that Gandalf is obviously sitting on, even though you can see him holding the front of it underneath his robes, and sometimes, you can see him holding a very thin bridle. But right at the end of the film, when you have the shot of Gandalf, Aragorn, Legolas, Gimli, etc. on horseback, you see Gandalf's feet in stirrups. (01:44:05)
Revealing mistake: When the women and children are evacuated to the Glittering Caves under/behind Helm's Deep, in the first shot, a hooded person leans on a stalactite making it sway back and forth. (02:42:00)
Revealing mistake: Frodo, Sam, Faramir and Gollum are at the sewer in Osgiliath when Faramir asks, "Cirith Ungol?" and then grabs Gollum's neck. Frodo and Sam watch as Gollum is grabbed, but their eyes do not follow Gollum as Faramir grabs him, their eyes remain focused on the ground to their left. The shot of Faramir and the shot of Frodo and Sam were edited together, with Gollum added later. (01:42:20)
Revealing mistake: When the men are retreating into the halls of Helm's Deep, you can see an archer in the bottom right corner repeatedly shooting his bow without an arrow on the string.
Revealing mistake: At the Battle of Helm's Deep, just after Aragorn slices the leg off the Uruk and just before Gimli slides down between the legs of another Uruk and smashes his axe into his chest, look carefully at the Elf on the left side of the screen. He arches his bow and fires, followed by a specific shooting bow sound effect, but there is no arrow. (01:05:30)
Revealing mistake: At Helm's Deep, in the 1st close-up, Gimli says, "You could have picked a better spot," and two particular Elves stand at his left. In the next wide shot as Aragorn approaches, the Elves to the left of Gimli are different Elves than in the previous shot. One of those Elves from the 2nd shot is seen close-up when Aragorn walks away. Also, the second row of Elves is much closer to the first row of Elves in the 1st shot. (01:00:25)
Revealing mistake: When Theoden, Aragorn, Legolas and the Rohirrim soldiers ride out to meet the enemy just before Gandalf's return, they charge down the ramp into the stampeding Uruk-hai. If you watch the Uruk-hai very carefully you can see that some are running in slow motion, even though the scene is played at normal speed. (01:29:10)
Revealing mistake: When the Ents are releasing the river, on the bottom left hand side, you can see an Orc chopping at an Ent. However, when the Ent moves, the Orc is still chopping the same place.
Revealing mistake: There are quite a few times where the Uruk-hai fitted skin wrinkles, creases or bubbles up where they shouldn't. Some examples are, at Helm's Deep, while they fight on the Deeping Wall, as the Uruks climb the ladders and when Gandalf charges with the Rohirrim. (01:05:30)
Revealing mistake: Right after Gandalf gave warning that they would not be welcome at Rohan and jumped forward with his horse, next after him Legolas moved forward before Aragorn, you can see Gimli that rode with Legolas was a fake Gimli, the color of his skin was not normal, and he was too stiff. (00:53:45)
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.
Revealing mistake: When Gandalf, Aragorn, Theoden, Legolas and Gimli all ride up the hill on horses towards the end, there is a man on a horse on the left of the screen. Who is he and why is he there? He's Éomer's body double (Karl Urban was unavailable) and at some stage they were going to put Éomer's head on him digitally, but they never got around to it. Director's commentary, extended DVD. (01:43:05)
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. (01:14:35)
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. (01:27:20)
Revealing mistake: When the Uruk-hai are running through the rock canyon while carrying the Hobbits, the Uruk with the painted white hand on his face holds up his right fist. In the theatrical release and regular DVD, a second Uruk then asks of the painted one, "What is it, what do you smell?" and he answers, "Manflesh." The very next shot is of Pippin saying, "Aragorn," followed immediately by the second Uruk saying, "They've picked up our trail." The Uruk who should have the painted hand on his face no longer does. He gives a low growl, then all the Uruk-hai run again. However, in the extended DVD, same scene, when the painted Uruk holds his fist up, it cuts to the Orcs hiding behind the rock, and the very next shot is of those two Uruks, and just like in the regular DVD, the Uruk who is supposed to have the painted hand on his face, does not. It is that Uruk who later in the scene says, "Manflesh," and unlike the regular DVD, without the painted hand on his face. Side note: It may be a different Uruk standing next to the 'second Uruk', in the questionable shots and that's why he doesn't have a painted face, but either way, it's still a mistake between shots. (00:14:50)