To create the effect of Oberyn's crushed skull, a dummy was laid on the floor with fake blood and Pedro Pascal's face was digitally added over the dummy's face in post production.
The first time that Oberyn Martell's nickname "the Red Viper" is mentioned onscreen.
In the previous episode Mockingbird (2014), Bronn (Jerome Flynn) analyzed how he might be able to win a fight against the Mountain: "Maybe I could take him, dance around until he's so tired of hacking at me, he dropped his sword, get him off his feet somehow. But one misstep... and I'm dead." Unknowingly, he seems to be summarizing how the fight between Oberyn and the Mountain would go: Oberyn initially confuses and wears out the Mountain by moving around him, attacking with quick jabs, until the Mountain is on his back without a sword. However, Oberyn makes a misstep by stepping too close to his opponent before delivering the final blow, which costs him his life.
Tyrion and Jaime discuss their cousin Orson, and Jaime comments there is no commonly accepted word for killing cousins. He refers to their cousin Alton Lannister, whom he killed in A Man Without Honor (2012) to escape captivity. In the books, they never discuss their cousins, and Jaime never kills a family member; the closest he comes is when his first cousin Cleos Frey helps him escape from the Stark forces, but is subsequently killed by outlaw archers on their way to King's Landing. Not only does Jaime not express any sadness over Cleos' death, he also strips him of his weapon and leaves the body for the crows and looters.
The episode won an Emmy Award for outstanding art direction for a single-camera series.