Trivia: The horse heart that Daenerys eats was actually made of gelatin, and genuinely tasted dreadful - her physical revulsion at eating it is real. It had dyed pasta to simulate veins, and was injected with fake sugary blood, which attracted flies. The blood was so sticky and ended up covering Emilia Clarke to such an extent that after filming it glued her to the toilet seat.
Trivia: Cersei remarks to Tyrion that she had heard his nose was cut off during the Battle of Blackwater Bay. This is a reference to the books, in which part of Tyrion's nose was indeed cut off.
Trivia: After the destruction of King's Landing, the white horse that Arya finds is the very same white horse that belonged to Strickland, the leader of the Golden Company. Note the horse's identical muzzle markings. (00:32:25 - 01:18:10)
Video 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.
The Mountain and the Viper - S4-E8
Trivia: Towards the end of this episode, Tyrion and Jaime have a discussion about their brain-damaged cousin Orson. This is supposedly a swipe at Ender's Game author Orson Scott Card, who is a harsh critic of the show.
Trivia: The dead stag that the Starks discover was not a prop. Apparently it had been dead for two days, and the smell was revolting to the actors.
Answer: Basically it's because he broke his vow. A member of the Kingsguard is sworn to protect the king at all costs. Jaime elaborates more on the deed to both Catelyn Stark and Brienne of Tarth, telling Catelyn that no matter what course of action he took, he would be breaking one vow or another (i.e. if he obeyed the king, he would conversely be disobeying his own father), and telling Brienne that the Mad King was planning on burning all of King's Landing, but he did not bother to tell Ned Stark that. Ned Stark felt that killing Aerys was dishonorable and excessive. Robert Baratheon still could have usurped the throne without Aerys being killed.
Phaneron