The Iron Throne has been greatly redesigned from Game of Thrones (2011). It is larger and more asymmetrical to more closely match the description in George R.R. Martin's novels, although it is still nowhere near that big: the throne in the books is a 40-foot, immovable, asymmetrical behemoth made from 1000 swords welded together, with the seat 20 feet above the ground, and only accessible by a flight of stairs; the person sitting on it addresses people down below from 40 feet away.
In Season 1 of Game of Thrones (2011), George R.R. Martin, the author of A Song of Ice and Fire, wanted his prop head on a pike, but due to budget limitations they couldn't afford it back then. In a recent podcast, Ryan J. Condal (Showrunner of House of the Dragon) promised Martin that his head will be seen in House of the Dragon.
The Valyrian steel dagger carried by Viserys is the same one that is used in the attempt on Bran's life in the first season of Game of Thrones (2011), as well as used by Arya in the final season. Despite its significance in both shows, the dagger is rarely mentioned in the "A Song of Ice and Fire" book series, and is not mentioned at all in "Fire & Blood."
Paddy Considine stated Viserys' disease is a form of leprosy, and "It becomes a metaphor for being king, and the stress and strain that it puts on you, and what it does to you physically, what it does to you mentally."
On his personal blog, George R.R. Martin stated: "I expect to be involved in [House of the Dragon] to some extent... and, who knows, if things work out, I may even be able to script a few episodes, as I did for the first four seasons of GAME OF THRONES. But... let me make this perfectly clear... I am not taking on any scripts until I have finished and delivered WINDS OF WINTER. Winter is still coming, and WINDS remains my priority, as much as I'd love to write an episode of HOUSE."