Found a bunch of good tidbits in this video and article!
Despite being kept in the dark, Simpson was able to figure out the twist before everyone else. This was when the makeup artist “asked if my eyebrow shape could be changed. I then saw one of the creators an hour later and said ‘I’m thinking the only reason they would change my eyebrows is because they are trying to get me to look like someone else.’ She said to not tell anyone I knew that.”
Simpson does not know if he will be back for season two: “We now know the finish line for this man so I don’t know if there’s enough story to show. But I could see some interesting ways to bring him back. Like the corporate takeover, or his other heartbroken visits to the park. But I’d never suggest they just stick William in for no reason. The writers have told me that they know this story very well. I’m mostly invested in Dolores, cause I think she stands for so many things.” And will we ever see a scene where he can act alongside Ed Harris? Simpson imagines that “maybe William shows up as a host and has a scene with Ed?”