Continuity error: At the end of the episode, when Ramsay says that his hounds are loyal, Sansa answers that they were, but they haven't eaten for seven days. This echoes what Ramsay said at the meeting on the day before the battle, but when Ramsay said that, Sansa had already left the meeting, so how did she know he starved them?
In the season 5 finale, Jon Snow was stabbed a total of 6 times. However, in this episode, the death sentence was carried out only to 4 people. Which means 2 people got away unpunished!
Goof: During the final showdown with the Sons of the Harpy, Drogon gets three spears embedded in his back, which he cannot reach. The camera angle changes to reactions of the inner circle, then back to Drogon. Now, he has one spear in his back and one in the side of his neck, which Daenerys removes.
Hafþór Júlíus Björnsson is the third actor to portray Gregor "The Mountain that Rides" Clegane. The part was previously played by Ian Whyte in season 2 and Conan Stevens in season 1.
The title for this episode "Mhysa" is the Ghiscari (a bastard variety of Valyrian) word for Mother.
The title of this episode, "The Rains of Castamere" is a song that was written about Tywin Lannister after he had a whole noble family, the Reynes of Castamere, slaughtered.
Goof: When the bear breaks Brienne's wooden sword, half falls by the bear and she drops the handle where she's standing, but then there are three pieces and they're all suddenly about 10 feet behind her. Additionally, in the final overhead shot of the arena, the broken sword pieces have disappeared completely.
The title of this episode is the name of a popular, bawdy song in Westeros, "The Bear and the Maiden Fair", which tells the story of a bear seducing a fair maiden.
The title of this episode "Kissed by Fire" is a phrase commonly used by Wildlings to describe anyone with red hair. One such person is Ygritte.
The phrase "and now his watch is ended", which is the title of this episode, is actually uttered during the funerals of Night's Watch men.
The title of this episode "Dark Wings, Dark Words" is a reference to how most people feel about ravens (which are traditionally black feathered) which often carry messages with bad news. There are two messages delivered by ravens to Robb Stark in this episode, both of which carry bad news.
The burnt remains of Winterfell rise in the opening credits, reflecting the events of the previous episode.
The phrase "valar dohaeris", the title for this episode, is High Valyrian meaning "all men must serve". It is the traditional response to the phrase "valar morghulis", which was the title of the previous episode, the season 2 finale. "Valar morghulis" means "all men must die" in High Valyrian and is used as a greeting in certain parts of Essos. Along with Dothraki and Skroth, High Valyrian is one of the fictional languages created for the show by David J. Peterson based on what George R.R. Martin envisioned for his "A Song of Ice and Fire" novels which "Game of Thrones" is an adaptation of.
The phrase "valar morghulis", the title for this episode, is High Valyrian meaning "all men must die". It is a traditional greeting in certain parts of Essos. "Valar dohaeris" (which is the title of the next episode, the season 3 premiere), meaning "all men must serve", is the traditional response to it. Along with Dothraki and Skroth, High Valyrian is one of the fictional languages created for the show by David J. Peterson based on what George R.R. Martin envisioned for his "A Song of Ice and Fire" novels which "Game of Thrones" is an adaptation of.
The title of this episode "The Old Gods and the New" refers to the two main religions in Westeros. The Old Gods are worshiped in the North and the Faith of the Seven, also known as the New Gods, elsewhere in Westeros (except for the Iron Islands which has its own religion, the Drowned God). There are occasions where people swear oaths by "the Old Gods and the New" as well.
In the opening credits, Jack Gleeson, who plays Joffrey Baratheon, mistakenly has the Stark direwolf sigil next to his name.
The title of this episode is a direct quote from the books. Arya Stark refers to herself as "The Ghost of Harrenhal" in "A Clash of Kings", Chapter 30.
The title of this episode, "What Is Dead May Never Die", is quoted from the Iron Islander's religious worship of the Drowned God. The Iron Islanders, called Ironborn, often use it as a war cry, or even as a formal greeting.
In the opening credit sequence a new destination visited in this episode, Dragonstone, "rises" from the map. Vaes Dothrak and the Wall also rise although they are not visited in this episode, but there is activity by key characters in their general areas of the world.
The title of this episode, "Fire and Blood", is the Targaryen family motto. Each noble family has its own motto. For example, "Winter Is Coming", the title of episode 1 of season 1, is the Stark family motto.