Continuity mistake: In the opening shot of the stable scene, there is a saddle in the stall next to Brego. A few shots later, you see a man lifting that saddle and start to walk away. There is no saddle in the next few shots. Then the saddle is back again, for Éowyn to pick up. (Extended DVD.) (01:30:35 - 01:31:40)
Continuity mistake: At the destruction of Isengard, the dam is broken and the river is starting to break through the wall. In the wide shot as the river starts to break through, we see the wall breaking and all the CG Orcs at the top of the wall falling. In the next close-up, we see the CG Orcs still standing on top of the wall and when they do fall in this close-up, they fall very differently than in the previous wide shot. (01:31:55)
Continuity mistake: After Legolas leaps onto Arod, the men on horseback change in their arrangement, as they charge towards the Warg Riders. In one shot Gamling is just drawing his sword, while riding between Theoden and Legolas. Next shot is a Rohan rider directly behind Legolas. Then in the next shot of Theoden, it shows Gamling drawing his sword again, riding behind Legolas. (00:10:45)
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. (00:42:50)
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. (00:11:05)
Continuity mistake: At Henneth Annun, Frodo and Sam have their blindfolds removed, and in this wide shot, behind them to their right one of the Rangers throws a cloth onto a crate that has objects lying on it, and sits down on the sack. In the semi close-up shots of Frodo and Sam, the cloth the Ranger threw lies differently and the things lying on the crate are different too. No one touched them. (00:28:55)
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. (01:45:25)
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. (01:41:50)
Other mistake: At the very end of the film, where Sam, Frodo and Gollum are approaching Mordor after leaving Osgiliath, it pans up over the mountains to reveal Orodruin (Mt. Doom) in the foreground to the right and The Tower of Barad-Dur in the background to the left. According to Tolkien's maps, as seen in the prologue to the Fellowship of the Ring, if they were approaching Minas Morgul from Osgiliath, Orodruin would be to the left and Barad-Dur to the right.
Other mistake: When Aragorn & Gimli are being pulled up the wall after defending the gate at Helms Deep, Gimli is a puppet (A very good puppet though.) when you see him in Aragorn's arms just before they get pulled over the top by Legolas, only a quick shot but still visible.
Continuity mistake: Helms Deep's gate is destroyed by a battering ram, and shorn up like a barricade while Aragorn and Gimli hold back the orcs. However, when the orcs finally burst through the gate, it has reverted back to a fully intact gate that opens as if on hinges.
Continuity mistake: Just after the Warg knocks Hama off his horse, in the wide shot, Hama is lying in short green grass and his sword is flat. Then in the first close-up of Hama, he is lying in thick, tall, yellow patches of grass and his sword is sticking way up to his left. (00:08:50)
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)
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. (00:42:45)
Continuity mistake: As the people are fleeing from Edoras, many shots are shown of Eowyn, and frequently her hair is arranged somewhat differently. (00:08:15 - 00:10:00)
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)
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. (01:31:40)
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. (01:14:15)
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. (00:10:30)
Answer: The movie makes it clear that Gandalf has lost some of his memory and his personality has changed. Gandalf actually did die and pass over to the "other side", as it were but was sent back to complete his task. However, he was sent back as a similar, but different entity. Gandalf the White does not have all the memories of Gandalf the Grey, at least at first. He doesn't even remember that he used to be called Gandalf the Grey until someone points this out to him. It is implied that Gandalf doesn't even remember Sam until Aragorn mentions him. Gandalf then searches his memories and remembers who Sam is and his eventual importance to Frodo's quest. When he finally remembers this, he is pleased that Sam went with Frodo, as he will play a crucial role near the end of the journey.