The episode won an Emmy Award for outstanding art direction for a single-camera series.
The first time that Arya recites her 'kill list' on the show. It is much longer in the novels, the full list being: Weese, Dunsen, Chiswyck, Polliver, Raff the Sweetling, the Tickler, Sandor "the Hound" Clegane, Gregor "the Mountain" Clegane, Amory Lorch, Ilyn Payne, Meryn Trant, Joffrey and Cersei.
There is no character named Talisa of Volantis in the novels. She replaces Jeyne Westerling as Robb Stark's love interest, a romance that occurred almost completely off screen in the book. While mapping out the season, showrunners David Benioff and D.B. Weiss initially included Jeyne, but as the character started to deviate significantly from her counterpart in the books, author George R.R. Martin suggested to make her a completely different character, and came up with her name 'Talisa'.
In the novels, Tywin and Arya never interact. At Harrenhal, Arya is first sent to work in the kitchens, using the name "Weasel" (the name of an orphan girl she had met on the road); after Roose Bolton takes over, she is chosen to be his cup-bearer, not Tywin's. She takes a glimpse at Tywin a few times, but never speaks to him, and he does not pay her any attention. On the show, the name 'Weasel' was given to the man who assists the Tickler in interrogating prisoners.
According to the novels, Littlefinger and Catelyn never encounter each other again after their previous meeting in the first novel, in which he falsely claimed that the dagger used by the catspaw assassin, who nearly killed Bran, belonged to Tyrion. In the book, Littlefinger is sent off to Highgarden to negotiate with the Tyrells, but Catelyn is no longer there. It is Cleos Frey, Jaime's cousin (who had previously negotiated between Robb and the Lannisters), who gets sent to Catelyn with Ned's bones when she is at Riverrun. He tries to negotiate an exchange of her daughters for Jaime, but admits under pain of death that they don't have Arya; he never suggests that she act behind Robb's back.