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: 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)
Continuity mistake: When Frodo and Sam are down below, near the Black Gate, wanting to run in, but Gollum is convincing Frodo not to, Frodo's pants have a couple of holes at the left knee. Later, when Gollum dives for the fish in the rocky stream, Frodo's pants don't have the holes at the left knee, as seen when he's walking with Sam. Frodo did not change his pants, and this is before they have spent the night, which is the scene right after this one. (01:06:00 - 01:36:55)
Continuity mistake: Merry wakes up to find Pippin drinking the Ent water. During this scene, Merry's cloak changes, to either with or without leaves on it and the amount and position of the leaves vary too. (01:08:15 - 01:10:00)
Continuity mistake: When the Berserker Uruk-hai with the torch runs to the bomb to detonate it, Aragorn yells at Legolas to stop him. Legolas fires an arrow with green short fletch (feathers), then you see the berserker hit by a long white fletched arrow, the kind the Lothlorien Elves use. A second time, Aragorn yells to Legolas to kill him, and then again, the arrow shot by Legolas is not the same type as the one that hits the Uruk-hai. The Uruk is not hit by arrows of another Elf, it is Legolas that hits him, twice. (01:08:50)
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 - 01:17:30)
Continuity mistake: When the berserker Uruk-hai runs with a torch and Legolas is trying to kill him, we see that Legolas has only one arrow left on his back in the first shot, but in the second shot he has three arrows left. (01:08:55)
Continuity mistake: During the battle of Helm's Deep, a line of Uruk-hai with shields and a battering ram march up the causeway to the Keep. Then the wall below is breached, and in one shot of the wall exploding you can see, off to the right, that the Uruk-hai have reached the top of the causeway and are just standing there. Then in the close-up of the Uruk-hai on the causeway, they haven't reached the top yet. (01:09:10)
Continuity mistake: Merry's shirt is untucked under the front bottom of his vest when Pippin chases him and then as he sits on the roots of the tree. The tree starts to devour them. Just after the shot of hairy Hobbit toes, there is a close-up of Merry's jacket and vest, before panning to his face. It shows that his shirt is now tucked in, as well as in the far shot later, when Treebeard rescues them. (01:10:10)
Continuity mistake: Gimli yells, "Aragorn!" then as he jumps into the air, on that same wall, is a dead body hanging over the edge, next to the smoldering lantern. In the earlier shot, just before Aragorn lifts his head down below, as the camera panned over the Deeping Wall, there was no dead body lying at the top near the edge, next to a smoldering lantern. (01:10:20)
Continuity mistake: After the tree has buried Merry and Pippin in its roots, the close-up of those roots (gnarled and twisted) do not look anything like the roots of the tree in the far shot (straight and broad), when Treebeard says, "Away with you, you should not be waking." Not a case of distance - in the wide shot when Treebeard arrives, just after they're let go, you can compare that shot to the shot just before, and the roots are very different, regardless of the Hobbits' size. (01:10:45)
Continuity mistake: Just before Legolas surfs the shield down the stairs, he is holding the shield in his right hand and his bow in his left hand, which is down. In this shot, he starts to toss the shield down onto the ground, still clutching the bow in his left hand. In the next consecutive wide shot, the shield is still in mid-air, and as he is starting to run towards the moving shield, Legolas does not have the bow in his left hand now. He did not throw the bow over his shoulder. The next shot is a close-up of his feet on the shield, just starting to come to the stairs. In the next wide shot, as he is starting to surf at the top of the stairs, Legolas has the bow in his left hand again and he is lets loose the arrows at the Uruk-hai. (01:11:00)
Continuity mistake: As Legolas surfs down the steps, we see some dead bodies at the bottom of them, which he surfs right over. A few shots later, we see an aerial view of the wall with those same steps and there aren't any bodies at the bottom of the steps. (01:11:05)
Continuity mistake: Gimli is lying with his face under the water, after jumping off the Deeping Wall and landing on the Uruk-hai. In the close-up, the right arm that grabs Gimli's shoulder to help him out of the water is Legolas' right arm. Yet, in the wide shot, suddenly it is Aragorn helping Gimli to his feet, not Legolas. (01:11:10)
Continuity mistake: When Merry and Pippin are at the Entmoot, in several of the front coverage shots, Merry is several feet in front of Pippin and slightly to the left. From the back at a distance, however, they are next to each other with Merry on the right. While there are some shots in which they are both moving around, accounting for the difference, here they are both stationary. Extended DVD, Disc 2. (01:11:50)
Continuity mistake: When Aragorn, Gimli, Legolas and Gandalf are galloping towards Edoras, then stop and when they are riding up towards the entryway at the bottom of the hill, Shadowfax has a white rope around his neck. However, as they're riding through Edoras, passing the people, Shadowfax no longer has the white rope around his neck. (01:12:30 - 01:16:20)
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. (01:13:35)
Continuity mistake: At Edoras, after the first close-up shot of Éowyn kneeling at the bedside of Theodred, there is a front wide shot. In that shot the animal skin rugs going around the bed differ in position from the next wide shot behind Éowyn. Note especially, the rugs at the foot of the bed on the opposite side of Éowyn. (01:13:40)
Continuity mistake: When Legolas and another Elf are dragging Gimli back to the Keep, in the front view the Elf's quiver is empty. Yet in the next shot from behind, the Elf has many arrows in the quiver on his back. The arrows would be seen from the front, because they are way above his shoulder in the back shot. (01:13:40)
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)
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.