With almost 10 million viewers, this episode was the most watched series premiere in HBO's history.
The dagger carried by Viserys, which is seen in most of the season episodes, is the same one used by the catspaw assassin who attempted to kill Bran in The Kingsroad (2011), and also the same one used by Arya to kill the Night King in The Long Night (2019). In the book "Fire & Blood" there is no mention of it.
The title of the episode is directly taken from the chapter's title from the book "Fire & Blood", on which the show is based.
It is revealed that Aegon the Conqueror was fully aware of the Long Night and the coming invasion of the White Walkers, after seeing a vision in one of his dreams called 'the Song of Ice and Fire' (which is of course the name of the novel series that Game of Thrones (2011) was adapted from). He then made sure that this information was handed down from one Targaryen ruler to the next, so that they would be ready when the event occurred. It is thus implied that this tradition ended with the deaths of the Mad King and his intended successor Rhaegar, and the prophecy was never imparted onto Daenerys, which is why she needed to be convinced that the Night King's army of the dead was real.
The music in the end credits is "A Song of Ice and Fire" by Ramin Djawadi, which is also the music from the closing credits of the series finale of "Game of Thrones," The Iron Throne (2019). It appears in the original soundtrack of the eighth season of GoT.