Revealing mistake: In Shelob's lair Frodo runs away from her and points the light of Eärendil at Shelob to keep her at bay. He then dives, head first, down a sloped passage and as he does both of his knee pads are seen. (01:42:10)
Revealing mistake: At Minas Tirith, Grond breaks through the door, then Trolls and Orcs attack. After Gandalf yells, "Volley! Fire!" there is a shot of Orcs, one of which is somewhat bald at the bottom of the screen in the foreground, who run towards the right of the screen. Then other shots including Gandalf slaying a Troll. The last shot of this scene is the same shot of the Orcs running to the right of the screen. (01:48:15)
Revealing mistake: At Minas Tirith, Grond destroys the door and the Trolls attack. Gandalf charges at one Troll in particular and proceeds to slash the Troll in the belly, and the Troll drops down, yet Gandalf's sword never even touches the Troll at all. (01:48:30)
Revealing mistake: In Minas Tirith, as Gandalf slashes at the Troll to his right with his sword, his left foot disappears and reappears in the Troll to his left. The stirrup under his left foot is completely visible at that point too. (01:48:30)
Revealing mistake: After Sam rolls down Shelob's back, he holds Sting up towards Shelob and as she advances forward Sam trips and falls back. In the shot facing Sam as he falls, when he hits the ground his left knee pad is seen. (01:51:05)
Revealing mistake: After stabbing Shelob the last time, Sam picks up the light of Eärendil and trips near Frodo's body. As Sam hits the ground his right knee pad is visible. (01:52:00)
Revealing mistake: During the charge of Pelennor fields, when the Rohirrim are fired upon and when they clash with the Orcs, in many shots either the Rohirrim, horses' bodies or Orcs partially disappear and may reappear within the melee. For example, when the riders are fired upon the real horses run right through some fallen CG horses and riders and in another shot two Orcs' arms disappear as horses ride by. (02:00:10)
Revealing mistake: During the charge of the Rohirrim on the Pelennor fields, there is a close-up of Éomer. His spear is held in his right hand, he tosses it up and amazingly changes his hand position on the spear in mid-air as he rides. Another rider is behind Éomer to his left and as this man rides the spear he holds above his head bobs up and down like rubber, as does the spear behind Éomer's right shoulder. (02:00:30)

Revealing mistake: Trying to save Faramir, Pippin shouts, "Gandalf!" and in the first shot from behind Pip, he runs towards Gandalf, the Gondorian soldiers run towards the camera and he is perfectly Hobbit sized. However, in the next shot, facing Pippin, he is not only further away than in the previous shot, when he runs towards the camera as the Gondorians run past him, Pippin is now much taller, almost as tall as the soldiers he passes. (02:00:50)
Revealing mistake: At the end of the film in the shot from behind as Bilbo is walking towards Elrond and then up the boat ramp, we see the head of the "little person" playing the small version of him. His head is actually in a different proportion compared to the previous shots. The top of his head is considerably larger than before. (02:04:15)
Revealing mistake: On the Pelennor fields, the Rohirrim battle the Haradrim on Mûmakil with their bows and arrows. In one particular shot the Rohirrim in the foreground ride towards the right of the screen and the rider at the left lets loose one arrow, then reaches behind him to get another arrow and brings his arm back to the front. However, no arrows are ever visible in his hands. (02:05:20)
Revealing mistake: After Gorbag says, "You touch it, and I'll stick this blade in your gut," Shagrat and Gorbag start to fight. A few shots later there's a close-up of Gorbag who is bald, he's not wearing his hairpiece/wig in this shot, as he's being pushed towards the right of the screen by Shagrat, just before falling into the hole! (02:19:00)
Revealing mistake: When the combined Rohirrim/Gondorian army halt upon arrival at the Black Gate, Aragorn rides up and stops beside Legolas in the close-up. Éomer's double, who has a much fuller and longer beard, is blatantly visible behind Aragorn in this full frontal shot. (02:28:25)
Revealing mistake: After Aragorn demands, "Let the Lord of the Black Land come forth," as he says, "Fall back," Gandalf and Pippin, who wears his Gondorian helmet, are seen close-up. It is blatantly obvious that it is not Billy Boyd, but his scale double under that helmet, as the face is perfectly visible in this extreme close-up. (02:30:30)
Revealing mistake: When Sam carries Frodo on his shoulders and struggles to carry him up to the entrance of Mount Doom, just before he says, "Look Mr. Frodo. A doorway," you can see Sam's right latex Hobbit foot slightly peeled off from his skin near his toes, as he steps up onto the step. (02:35:25)
Revealing mistake: In the scene at the Black Gate when Sauron is assumed talking to Aragorn, when he turns around you can tell that Gimli is the scale double, Brett. (02:39:40)

Revealing mistake: In the scene inside Mount Doom after Gollum bites Frodo's finger off and it appears they have both fallen into the lava, Sam looks over the edge of the cliff and sees Frodo hanging on. Just after Sam says, "Take my hand!" as Frodo tries to grab Sam's hand, you can plainly see Frodo's "missing" finger bent in half to give the appearance that it is gone, complete with the blood and gore seen just after the finger was bitten off initially. (02:44:25)
Revealing mistake: After Aragorn is crowned king he greets Legolas and they place their hands on each other's shoulder. In the shot facing Aragorn when he starts to move toward Arwen, the semi profile seen on Legolas is not Orlando Bloom, but that of his double. In the previous shot facing Legolas, Aragorn and the Elf are the same height and eye level, but in the shot facing Aragorn, Legolas is considerably taller. (02:55:05)
Revealing mistake: When Legolas is climbing up the oliphaunt during the battle of the Pelennor fields, there is a shot of him moving along the oliphaunt's side. During this shot, he pivots a bit on the rope he is holding. When he pivots towards the side, you can see that the arrows in his quiver pass through the skin of the CGI creature.
Revealing mistake: At the stairs of Cirith Ungol, after Gollum says, "Come away, Hobbits. We climb. We must climb," there is close-up of Hobbit feet. The next shot as Frodo and Sam climb, is a flipped shot - just note the stew pot on Sam's back, it is on his left side, though he carries it on his right side. Sometimes, what gives away the reversed shots are the Lórien leaf brooches or Sam's pots and pans.
Answer: In the book, it absolutely was his birthday.
Brian Katcher
What chapter in the book where smeagol kills deagol?
DFirst1
The Fellowship of the Ring, chapter two 'The Shadow of the Past.'.
Brian Katcher