According to director Craig Zobel, Kate Winslet was the only actor confident enough to go back to her native accent in between takes; every other actor was terrified to let it go. For the cast and crew, witnessing Winslet immediately switch from a Delco accent to her normal English accent nonchalantly was an astonishing sight.
Audience viewership increased weekly, due to such positive word-of-mouth. On the evening of the finale, on May 30, 2021, the HBO Max streaming server crashed for several hours for the first time in its history, mere minutes from the episode airing. The finale episode became the most-watched episode in HBO Max history.
Evan Peters stated that the dynamic between him and Kate Winslet mimicked the dynamic between their characters- with Peters being intimidated and learning from Winslet. He was constantly amazed by how incredibly detail-oriented she was in preparing for the scene: "She would walk up to me and be like, 'Okay, so it's 2:38pm. We just came from the Deacon's place and we probably stopped for a coffee and lunch. Now we're here and we're doing this thing.' I would look at her and be like, 'Damn. Was I supposed to do that? I didn't prepare like that.'"
Kate Winslet and Julianne Nicholson are friends in real life. Nicholson's husband, Jonathan Cake, is the godfather of Winslet's son, Joe. Winslet recommended Nicholson for the role of Lori, and arranged a meeting to convince her to take the part, assuring her that she would regret it if she didn't accept. Brad Ingelsby knew that the actor that portrayed Lori had to be cast second, given how central the friendship is to the story.
Even though Mare was an athlete in her youth, Kate Winslet didn't want her to be overly fit in her 40s. "I didn't want to make her an impossible, superhuman 40-something-year-old. Most women aren't like that. We do what we can in the midst of the juggle of everything else."