Continuity mistake: When Bran is taken from his horse in the woods, there are 3 wildlings that attack. The first Rob cuts his throat, the second, Rob is holding the female wildling by the hair, he then spears and kills the third with his sword and the very next frame the 3rd wildling is then holding a knife to Bran's throat, unharmed. (00:11:15)
Visible crew/equipment: At the Wildling camp, before Jon and Ygritte go into the cave, there is a modern building, and clutter visible in the distance.
Continuity mistake: When Tyrion is explaining where he has been and what he has been doing, he grabs a jug of wine by the neck. When the camera changes he now has it by the body of the jug. (00:07:30)
Continuity mistake: When Ser Barriston throws his armour and sword on the floor after being demoted, the armor and sword are inside the black tiled square on the floor. Camera changes to show Sansa kneeling before the council and now the armor and sword are outside of the black tiled box despite no-one touching it. (00:52:30)
Continuity mistake: When Tyrion is talking to Sandor, his position in relation to the gate changes between camera cuts. In the first shot he is next to the gate. In the second shot he is about 3ft away. (00:06:20)
Continuity mistake: When Sam hands the bureaucrat the letter from Jon Snow, in the shots facing the bureaucrat, the wax seal is on the left side of the envelope (when seen from Sam's perspective). In the shots facing Sam, the seal is on the right side of the envelope.
Continuity mistake: When Ser Jorah tells Dany that her life with Khal Drogo "will get easier," watch the strap of her dress. It moves up and down her right shoulder throughout the scene. (00:03:05)
Continuity mistake: When the Faith Militant descend on Ser Loras Tyrell's training session there is a shot after the Militants have come down the stair of Loras fighting from behind a man's shoulder, in this shot you can see they are fighting on grass surrounded by walls with sheer drops with no entry point other than the stairs the militants walk down. In the next shot you can see the 9 militants that have come down the stairs approach Loras from one side, but suddenly 6 militants join him from the opposite side, where they definitely were not before. In the zoomed out shot you can see there is nowhere for these men to have come from. (00:11:15 - 00:11:50)
Battle of the Bastards - S6-E9
Character mistake: When Theon and Yara are given an audience with Daenerys, Tyrion remarks to Theon that when they last saw each other at Winterfell, Theon was making jokes about Tyrion being a dwarf. The mockery was actually the other way around: Tyrion mocked Theon for being a glorified and subservient hostage of the Starks, as well as taking potshots at the foolish strategy of the Greyjoy rebellion.
The Mountain and the Viper - S4-E8
Continuity mistake: When Oberyn first tells Gregor that he will make him confess to raping and killing his sister Elia and her children, he is holding his spear with both hands. In the next shot, he's holding it with just one hand.
Continuity mistake: When the camera pans out from Jon and Ygritte standing on the wall kissing, Tormund and Orell, who were sitting next to them, are nowhere to be seen.
Continuity mistake: When Jorah gets his royal pardon, the wax seal is hanging freely. Camera changes and now the wax seal is resting on his fingers. (00:31:00)
Cripples, Bastards, and Broken Things - S1-E4
Continuity mistake: When Ned and Petyr are walking and talking about Sir Hugh of the Vale, they are in brilliant sunshine in one shot then in an instant cut there is no sun. (00:28:05)
Revealing mistake: When we see Joffrey get attacked by the dire-wolf, You can see his arm suddenly has padding underneath his jacket. (00:47:20)
Audio problem: When Tyrion is saying he wants to stand on top of the wall, it is an over the shoulder shot, however his mouth doesn't match up with what he is saying. (00:07:40)
Continuity mistake: At Daenerys' wedding we see a man get sliced across his midriff and lean backwards with his mouth open. Camera does an instant cut and now he is slouched forwards. (00:52:00)
Continuity mistake: In the scene in the amphitheatre, while seated in the royal box, Daenerys is wearing a full length white gown with flat pumps and an ornate silver necklace with a large dragon motif on the left side. During the revolt when she is seen running across the fighting pit the dress is shorter and she seems to be wearing some sort of leggings underneath it. Daenerys escapes on the back of her dragon and when we next see her in episode 10 she is wearing a completely different knee length pale blue gown. The necklace also seems different with her hair spread out on her left shoulder to disguise the lack of the dragon motif. She is also wearing grey boots with a fairly high heel. Obviously dragons come with a secret baggage compartment.
Continuity mistake: Towards the end there is a body of a dead Son of the Harpy lying between the fallen Unsullied and the side corridor visible in the wall, located very close to either. In the next show the body is gone. Also, as the camera angle changes, the blood stains on the walls look differently. (00:48:50)
Two Swords - S4-E1
Continuity mistake: When Arya and Hound come upon the murdered people Arya is riding facing left. After they pass, she is facing right. (00:48:40)
Chosen answer: Considering the show was in production for nearly a decade, it is hardly surprising that many characters were recast. Actors constantly move on to other jobs, creating scheduling conflicts. Some may not want to be tied to one project for so long a period, particularly for relatively minor roles that paid little money. As some characters became more prominent, the producers did recast a few roles with better-known actors. For example, Max Von Sydow replaced the actor who originally played the Three-eyed Raven. Some actors voluntarily left for personal reasons. Jennifer Ehle was originally cast to play Catelyn Stark but dropped out because she'd recently given birth. Other actors claimed they were replaced for "political" reasons. Here is a website with a rundown of which actors were replaced and why: https://screenrant.com/game-thrones-characters-recast-new-actors-every-why/.
raywest ★