Continuity mistake: Boromir gets hit by Lurtz's second arrow, drops down to his knees in front of Merry and Pippin, gathers strength, turns around and stabs an Uruk. In the next wide shot and close-up, he stands and is about to stab an Uruk in the back and the two arrows in his chest are there. Yet, in the next wide shot, as his blade is going down into the Uruk, Boromir has only the lower arrow in him, the one near his shoulder is not there, for 23 frames. In the next close-up, the upper arrow is back. These arrows are not CGI. (01:23:40)
Trivia: When the Hobbits enter Bree, right after the wheel of the carriage passes in front of them, there is a man you see to the right who's holding a carrot and burps. That is Peter Jackson making a cameo appearance.
Revealing mistake: Once the secret door to Moria is open, when Gimli says, "Soon Master Elf, you will enjoy the fabled hospitality of the Dwarves," as Gandalf leads the way inside, note the glint of the trailing power cord as it moves along the ground behind Gandalf and goes directly under his robe. This is the staff's electrical supply cable. (00:16:20)
Continuity mistake: When Gandalf pulls Sam in through the window at Bag End and throws him on the desk to ask him questions, several items fall off of the desk. The scene switches back and forth between Sam and Gandalf's perspectives several times. When Sam is shown, the arrangement and appearance of items on the floor below vary. In some shots there is a wooden box and book on the floor to the left side of Sam's head and/or a book and paper to the right. (00:40:50)
Continuity mistake: When Gandalf and Saruman are talking in Orthanc, we can see a black strap around Gandalf's fingers on the hand holding his staff. In some shots it's around different fingers, in others it's disappeared completely. (00:46:20)
Continuity mistake: At Dwarrowdelf, as Gimli runs into the Chamber of Mazarbul toward Balin's Tomb, just past the doorway we see a long stick and a very short axe leaning on the right wall. Later when Legolas says, "Orcs!" Boromir runs to the door and now we see a long handle axe with the big blade on top, leaning on that same wall. This does not refer to the two axes in the corner. (00:25:05)
Visible crew/equipment: After Gandalf removes the One Ring from the fire and places it in Frodo's hand. The large overhead set light is reflected in the Ring, above Frodo's reflection, as he turns it between his fingers in the second close-up of the Ring. (00:37:20)
Continuity mistake: When Gandalf meets Frodo for the first time and gives him a ride into Hobbiton on his wagon you can see that at the start of the sequence his wizard's staff is near Frodo's shoulder. In the back shot as they go over the bridge and another shot, the staff is to the rear of the wagon. In the very next shot, a close up, the staff has reappeared near Frodo's shoulder again. Also, as Gandalf goes up the hill in front of Bag End, his staff is sticking out the back of the wagon, but in the following close-up as he stops the wagon, the staff is right next to him. Other contents of the wagon also change position during the journey. (00:11:25)
Continuity mistake: When Haldir says, "Welcome Legolas, son of Thranduil," the outfit that Legolas wears is not the same in these shots than in the previous and following shots. Gimli's hair/beard are not as full and his prosthetics are a bit different too. Apparently this scene was one of the first to be filmed, but they realized later that this outfit wasn't working for the role of Legolas, so they changed it. Commentary on extended DVD. (00:45:30)
Visible crew/equipment: During their fight at Orthanc, in the wide overhead shot, as Saruman flies backwards towards the large doors, the wire attached to the back of Christopher Lee's outfit is visibly pulling his clothes. (00:50:45)
Continuity mistake: When Saruman and Gandalf start to battle at Orthanc, the first time Gandalf points his staff, he causes Saruman to slam onto his back. In the close-up of Saruman, the white wrap around the palm of his hand and wrist is perfectly visible on his right hand. He does not wear the wrap on his hand in the previous and most of the following shots. (00:50:25)
Visible crew/equipment: When Saruman points both staffs at Gandalf, he says, "I gave you the chance of aiding me willingly, but you have elected the way of pain!" as Gandalf spins round on the floor, with his left leg raised in the air. As he spins, there is a bulge at his side and the apparatus with the wire, around his left ankle, is perfectly visible. (00:50:55)
Continuity mistake: In one shot of Gandalf's first appearance at Bilbo's front door, he is wearing light-brownish shoes under his robes, and when he walks in, he's got his normal grey ones on. (00:15:00)
Continuity mistake: During the scene when Isildur cuts the Ring from Sauron's hand, it is obvious that he is against a pretty tall rock wall. But, when we see an overhead shot of the Dark Lord exploding, there is no rock wall. Notice how there are soldiers all around the explosion. (00:04:00)
Continuity mistake: At Balin's Tomb, in two shots Pippin backs up towards the stone well, and when the skeletal head falls into the well we see a part of the sticks behind the pail, lying on the well. In the shot from above as the body falls in, and in the close-up of the chain and pail falling in, the sticks aren't there. In the next shots of the stone well we see the sticks lying there. (00:26:25)
Revealing mistake: At the end of the film, there is a shot when Aragorn fights an Uruk-hai, just before Aragorn's back is up against the tree (before Legolas shoots six Uruks in a row). Look at the Uruk-hai's left arm, Aragorn rips two big holes with his fingers, in the Uruk-hai's skin. (01:21:20)
Continuity mistake: In Boromir's death scene, when Aragorn puts the sword into Boromir's hand, Aragorn's finger with the ring on is covered in blood. When we see his hands on Boromir's chest a second later, the blood has vanished. (01:23:50)
Continuity mistake: At the end of the Amon Hen battle scene, where Boromir has been shot by Lurtz, there is a close-up of Lurtz's feet (as if from Boromir's POV) showing Lurtz striding over and stopping in front of him. The ground is clear all around his feet. The shot then changes to a wide shot, from the side, and there are orc corpses piled up all around. None of these were visible before, but should have been. (01:21:20)
Continuity mistake: When Arwen is carrying Frodo to the Ford, during the close-up of his face, it is covered in a green slime/pus-type substance (coming out of his eyes and mouth). At the Ford when Arwen confronts the Black Riders, his face is clean. [Peter Jackson has stated that the pus was used in one scene and afterwards they decided it was too gross and didn't use it again. That's why it appears and disappears. Still a mistake though.] (01:18:15)
Continuity mistake: At Amon Hen, Merry and Pippin run from the Uruk-hai after distracting them from Frodo's escape. After they run over the bridge, the next shot is of the two of them stopping short when Merry sees more oncoming Uruk-hai. In this shot it is only Pippin's Elven brooch that is facing the opposite way it normally faces. (01:20:55)
Answer: "Fly, you fools"