Other mistake: During the scene in the banquet hall, as Tormund says "most people get bloody murdered, they stay that way", look at Daenerys in the background - a disposable coffee cup is on the table in front of her. This brown cup with a white plastic lid is nothing remotely like the style of cups they're all drinking from in the scene. HBO acknowledged the slip up and digitally edited it out on streaming services, reruns and future DVD releases.
Continuity mistake: In this episode, Kings Landing is shown as sitting on flat, plain-like terrain. In previous seasons, it was shown surrounded by water and mountains covered lush greenery.
Continuity mistake: When Jon and the others emerge onto the other side of the wall, there are 4 people with torches. Pay attention to the one at the back on the screen left. He has his torch in his left hand in this shot, but as the shot changes to the front he now has his torch in his right hand. (00:44:30)
Trivia: One of the severed heads on a spike is that of former president George W. Bush. Before shooting the scene, George RR Martin asked writers and producers David Benioff and D.B.Weis to have a cast of their 3 heads to be put on the spikes, but for budget reasons they opted to get a box from HBO's warehouse with used severed heads. They noted that one was Bush's, but they put a wig on it and got away with nobody noticing. In the Blu-Ray commentary the producers revealed the story, and got a lot of criticism from the right.
Continuity mistake: Ser Jorah has just given Daenerys 3 books as her wedding present. As she takes them, their spines are pointing towards her right side. Cut to the next shot, as Jorah informs her that he served her father, the spines are now pointing towards her left side. (00:50:45)
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 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)