Continuity mistake: When Tyrion wakes up inside the skycell you can see two skylights in the ceiling of the cell through which the sunlight passes. However, when we get a long shot of the skycells, you can see there's no way for the light to pass through them, as there are no "holes" on the floor of the cells above Tyrion's. (00:13:45)
Continuity mistake: When Ser Vardis has cornered Bron right at the edge of the moon door the position of Bron's body changes between shots. When the shot is taken from inside the moondoor, Bron's body leans backwards, over the moondoor. But when the shot is taken from behind the throne Bron is leaning forward.
Continuity mistake: At the climax of the Red Wedding massacre, Robb crawls towards his dead wife Talisa from the direction of the doors, which are at the opposite side from Walder Frey's throne. Robb turns Talisa onto her back from her left side (ie. he is on the right hand side of her body), and looks down at her face. This means that Talisa is lying in such a way that, if facing Walder's throne, her head is on the right and her feet on the left, towards where Catelyn is holding Walder's wife hostage and pleading for Robb's life. However, when Walder refuses, Robb has changed position and is now on the left side of Talisa's body, which is presumed to be facing the same direction as before as there is no reason for it to have changed. Robb then turns towards Catelyn who is still on the left side of the room (if facing from The Door), and is stabbed by Roose Bolton. As Robb collapses to his death, looking directly at Catelyn, he lands next to Talisa, whose head is now closest to Catelyn with her feet facing the other way, meaning that her body has somehow rotated by 180° in a matter of seconds. This is an especially bad mistake considering that several people have claimed the Red Wedding was completed in one take, which is not possible if this error exists unless Oona Chaplin for some reason decided out of boredom to play spin the bottle with her own body while out of shot, which would have interfered with Richard Madden's position anyway. (00:47:00 - 00:50:00)
Revealing mistake: At the beginning of the episode, Robb and Blackfish Tully are pushing Hoster Tully's funeral boat down the river. When they climb back onto the dock, there is already a trail of water going from the steps and ending where Robb ends up standing. None of the other characters standing on this portion of the dock have wet clothes, meaning none of them went into the river, indicating that the trail of water was from previous takes.
Continuity mistake: When the Sand Snakes attempt to kidnap Myrcella, as Nymeria Sand runs up to Myrcella to seize her, she is holding her large whip in her right hand. However, in the very next shot, the whip has disappeared, and Nymeria is now holding a dagger in her hand instead.
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)
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)