George R.R. Martin wrote Tyrion's sentence "I'll lead the attack" in the script only once. It was Peter Dinklage's idea to say it twice: once quietly to himself (almost surprising himself) and once so all the soldiers could hear.
This is the first episode of the series to take place in a single location (King's Landing) and at the time of its airing, featured the smallest number of main/recurring cast members.
In the early stages of development for season two, the Battle of Blackwater was to take place mostly off-screen for budgetary reasons, only showing the scenes of Cersei and Sansa in Maegor's Holdfast. However, showrunners David Benioff and D.B. Weiss felt that depicting this vital battle was important for the show. Wanting to avoid a recurrence of Baelor (2011) where the Battle of the Green Fork had to be omitted at the last moment when money and shooting days had run out, they started planning 'Blackwater' even before director Neil Marshall (who replaced the initial director) became involved, and cut corners on other episodes wherever possible to save budget. They also successfully lobbied HBO for an increased budget to film the battle after some "intense" negotiations.
This episode was Peter Dinklage's submission in the Supporting Actor in a Drama Series category in the 2012 Emmy Awards- his second nomination for the show.