This episode, where Tyrion kills his father Tywin, aired on Father's Day 2014. Tyrion ironically uses the crossbow of his purported victim Joffrey; it is the same weapon that Joffrey showed to Margaery in Dark Wings, Dark Words (2013) when shooting the mounted head of the boar that killed his father Robert.
This is the third season finale in a row that Arya's last line in it is "Valar Morghulis", following Valar Morghulis (2012) and Mhysa (2013).
Due to strict Icelandic laws regarding the importation of animals, the production could not transport the horses that Brienne, Podrick, Arya and the Hound had been riding on in the previous episodes. Local Icelandic ponies were not suitable due to the height difference, which is why it is explained that Brienne and Podrick's horses may have escaped or been stolen. Actual ponies were used in the background for Arya and the Hound's horses while they are camping, since the camera perspective didn't reveal their actual size.
The first time that the name of any of Daenerys' dragons is mentioned on screen: the black one is referred to as Drogon, named after Daenerys' late husband Drogo. The names of the other two still have not been mentioned: in the next episode, The Wars to Come (2015), the green one is named Rhaegal after Daenerys' older brother Rhaegar, and the white one is named Viserion after her other brother Viserys. According to the writers, the dragons have had the same names as in the books from the beginning, but they had difficulties in spontaneously introducing them in dialogue.
The song "The Rains of Castamere" can be heard in the soundtrack during Tywin's death scene. The song was famously composed to commemorate Tywin's victory over the rebellious house Rayne, and to serve as a reminder of what awaits people who cross the Lannisters. Ironically, Tywin now pays that price himself, for betraying his own son Tyrion.