Revealing mistake: When Sam and Frodo are talking after Sam called Gollum "Stinker," you can see, in some of the shots, Sean Astin's brown hair under the golden wig. (01:37:00)
Revealing mistake: The scene at the top of Saruman's tower when he is looking down watching the Ents is shown in reverse. His hair is the giveaway, blowing the wrong way. After cutting away to the Ents once more, they reversed the film again, when he is walking backwards.
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: 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. (00:50:50)
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.
Revealing mistake: The braids over Legolas' ears on his scalp, change drastically in position, shape, amount of hair that's braided and how it is braided, as does the amount of his side hair that is swept up into the back braid, in consecutive shots! The hair differs considerably in the following shots. In the armory, when Legolas and Aragorn argue and when Legolas apologizes to Aragorn, for despairing. When Legolas watches Aragorn hugging Haldir. When Legolas stands with Aragorn and Gimli on the Deeping Wall, awaiting the Uruk-hai. As Legolas lets loose the arrows towards the Berserker Uruk-hai. In these two shots too. First, standing outside of Fangorn with Aragorn and Gimli (flipped shot). Then, in Fangorn, saying, "This forest is old..."(flipped shot). (00:58:15 - 01:00:35)
Revealing mistake: Sam says "There's only one way to eat a brace of coneys" and in the next close-up, Sam stirs the stew. The rolled up blanket is behind the hanging pot, which means it's on Sam's right. In the next three shots, Sam's pack is behind the pot, not the rolled blanket, to Sam's right. Then, in the next close-up of the pot, it's the very same close-up shot as before, only it's been flipped, and the rolled blanket is there, near the pot again, this time to Sam's left. (01:41:40)
Revealing mistake: In the shot where the Rohan refugees are heading into Helm's Deep, the scale of the shot is wrong. On the right side of the screen, the refugees walk up the ramp into the gatehouse and on the left side of the screen, the Deeping Wall extends, with figures moving along the wall. The Deeping wall should be about even with ramp up to the Keep, if not a little bit forward, which means the figures along the wall should be at least the same size as the figures walking up the ramp. However, the figures along the wall, are much smaller, as if the Deeping Wall was pushed back further than the ramp. The right side shot was filmed as live action and the left side shot was filmed using the miniature of Helm's Deep and then the shots were merged together. (00:11:25)
Revealing mistake: When Treebeard throws Merry and Pippin they fall flat on the ground, at the feet of the White Wizard. In the shot when they both look up as they lie there, there are two circular bare earth mounds, right between each pair of their feet. These round areas of dark earth are surrounded by earth that is covered in leaves and bramble everywhere else. It is obviously where the actors' feet were positioned at the start of this shot, when they threw themselves to the ground. (00:41:35)
Revealing mistake: In the shot after Gimli shouts "Send them to me" at Helm's Deep, you see the elf closest to the camera fire an arrow. As he reloads, his right forearm passes though the bowstring. (02:09:05)
Revealing mistake: Soon after the Uruk-hai breach the wall with the ladders, Aragorn uses his sword to slice the leg off of one of them. In the wide shot, the Uruk has leg guards on, but in the close-up of the leg being cut off at the knee, no guards are on that leg. Also, visible in the close-up, it is obvious that the 'leg' is prepped to be cut in half. (01:05:30)
Revealing mistake: During the destruction at Isengard, Treebeard says, "Break the dam. Release the river." While he says that, there is a close-up of the dam wall as the Ent pulls away the wood blockades. We see the water starting to spurt between certain stones. Then there is a wide shot of the area, and in this shot, the water does not start to spurt between the same stones or in the same manner as in the previous close-up. (01:31:50)
Revealing mistake: During the Warg battle, as Aragorn slices off the head of a Warg rider, in the background on the hill there are two Rohan riders on horseback, one on a brown horse, one on a white horse, riding down the hill chasing after Orcs on foot. There are many shots after, including Aragorn throwing the spear into the Warg saving Gimli, and Theoden stabbing the Warg in his mouth. The next shots of Aragorn are when he stabs a Warg rider. The background plate is the same hill and the same two Rohan riders on horseback are still riding down the hill chasing after the Orcs on foot. Obviously these two pieces of footage were shot consecutively and were cut and separated, and other various shots were inserted in between them. (00:11:35 - 00:12:20)
Revealing mistake: In the two scenes, when Frodo and Sam are both up on the rocks and later, down below, hiding out of view, the Black Gate is in front of them. Earlier, is the view inside the gate. The two Trolls are pulling and pushing the wood 'pulley', to open the gate, while walking on the tall ramp that curves around. When the gate is open, that ramp should be in full view, from the angle that Frodo and Sam are positioned, but it is not. (01:03:55 - 01:05:55)
Revealing mistake: In Emyn Muil, just after Frodo says, You will lead us to the Black Gate," Sam and Frodo are following after Gollum. You see Frodo, with Sam trailing, come around a large rock formation from the left of the screen, then Frodo passes a large round boulder on his right and starts to run down a slope towards the camera. As Sam passes the same large boulder on his right, you can see it shake from him brushing against it. (00:13:40)
Revealing 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 - 00:52:55)
Revealing mistake: The very first shot of the Uruk-hai running through the rock canyon is the exact same shot that is shown in the last shot of this scene, just after Pippin bites the Lorien brooch off his cloak. Even though in between those two shots, all the Uruk-hai have been running until they meet up with the Orcs. In between those two shots, the rock formation shown behind the Uruk who lifts his fist up is also quite different in the next successive shot, when the Orcs approach the Uruks. (00:14:40 - 00:16:50)
Revealing mistake: Éomer yells, "To the King!" at Helm's Deep and the Rohirrim begin to ride down, towards the Uruk-hai. In the very first wide shot of Gandalf, starting to lead them down, there is a clear reflection of three of the riders and their horses, shown on the ground. (01:29:55)
Revealing mistake: Legolas runs down the hill to kill the Orc scout. As he is slicing the Orc's throat, in the close-up of Legolas' blade, one frame shows the position of the sharp edge right up against the Orc's throat, but the next frame shows that the sharp edge of the blade was turned away from the Orc's neck, just before the slicing, so as not to harm the Orc actor. This can only be seen frame by frame. (00:09:10)
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.
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.