From co-creators Sam Shaw and Dustin Thomason, the Hulu original Castle Rock is a psychological horror series set in the Stephen King multiverse, where good and evil, and darkness and light, are brought out in the residents of the small Maine woodland town. And in Season 2, budding psychopath and nurse from hell, Annie Wilkes (played to perfection by Lizzy Caplan), gets waylaid in Castle Rock and finds herself in the middle of the battle between the Merrill crime family and the Somali community.

During this 1-on-1 phone interview with Collider, co-showrunner Dustin Thomason talked about how Annie Wilkes (made famous in Misery) came to be at the center of Season 2, developing the backstory for such an iconic character, the valuable information they got directly from Stephen King about his creation, what made Lizzy Caplan their Annie, why Elsie Fisher was the perfect counterpart, how Ace Merrill (Paul Sparks) made his way into the story, getting Tim Robbins to sign on, working with already existing Stephen King characters vs. creating new ones, and the plan for possible future seasons.

Check out the interview below and click here for Dave's review of the new season.

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Photo by: Dana Starbard/Hulu

Collider: How did you come to the character of Annie Wilkes, as the focus for Season 2? What made you want to tell her story, specifically?

DUSTIN THOMASON: When (co-creator) Sam [Shaw] and I first started talking about the show, and we thought about the [Stephen] King universe and the sort of story that we didn't know and longed to know more about, Annie was always one of the first things that we talked about. What's fascinating about the book is that it's really Paul's point of view, almost exclusively. And then, in the movie (Misery), there's a little bit more of Annie's point of view, but the truth is that it really is Paul's story, and Annie is seen through his lens. And so, what felt exciting, when you're expanding the Stephen King universe and trying to think about the stories that one could attempt to fill in, Annie's origin story, and understanding more about her and how she got to that moment with Paul, always felt like a big opportunity for us. While Season 1 feels like a song written in the key of Stephen King, Season 2 runs a lot more into the heart of the canon, and Annie is obviously at the center of that. The opportunity to do a season, whether it was Annie or someone else that fills in one of the big, untold stories in the King canon, was always part of the project, from the beginning, to be honest.

When you're telling the backstory of such an iconic Stephen King character, who's probably one of his most famous characters, do you always have to keep what we already know about her in mind, or do you try not to think about that all the time, so that it doesn't completely overwhelm you?

THOMASON: What I would say is that, certainly, we always did keep it highly in mind. There was an Annie Wilkes bible that we had in the writers' room, and that all of the writers talked about, all the time. Part of what the inevitable question was gonna be was, how much freedom did we have to expand or fill in those margins? We know that Annie's from Bakersfield, and we know that she has a murderous past, and we know that she had a complicated relationship with her parents, but beyond that, we don't know too much more from the book, or from the movie. So, what we tried to do was to latch onto the details that felt really emotionally relevant to who she becomes, and to build from there. Rather than having to adhere to every detail, it was a question of, what part of the story felt like it defined who she was, and how could we build on that, from there? There was never a scenario where Annie wasn't gonna be a nurse, and there was never a scenario where Annie wasn't gonna be from Bakersfield, California. But in between those things, there was a lot of leeway, based on what Stephen gave us. It felt like that was the area we could scratch at, and hopefully get some exciting and emotionally rewarding payoffs from.

What was Stephen King's reaction to finding out that you wanted to explore that character and really dig into who she was, before we'd previously gotten to know her?

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Photo by: Dana Starbard/Hulu

THOMASON: He was, as always, and as every interaction with him has been, incredibly supportive. What was great was to have a little bit of his assessment of what she would be, as she was coming into her own, if you will. We got a little lens into where he felt she would be, at this point, and where he felt she would be, on her trajectory towards what she's going to ultimately become. That was incredibly valuable, and that was also something that we had blown up and put in the writers' room and constantly looked back at, especially whenever we got into a tricky situation, writing wise, in trying to figure out exactly what Annie's reaction to something would be, or what her action would be. We would always go back to Uncle Stevie's wisdom, and look at what he told us about Annie, which was stuff that wasn't in the books or in the movie. It was amazing to have this very small window into what he felt she would've been, when she was young.

As daunting as I would imagine it must be to take on and explore a character like this, on the writing side of it, I can't imagine what it must be like for an actor to take on this character, and Lizzy Caplan is just tremendous in this role. What made her your Annie? Was it something that you immediately saw, right away?

THOMASON: Certainly, I have always loved Lizzy, as an actor, and part of it is that she has such range. She's incredibly funny, and she's also capable of great drama and tragedy, as we've seen in Masters of Sex, and other roles. She has it all. Part of what felt exciting was that I knew that, in order to play Annie, somebody was gonna have to allow themselves to be very, very vulnerable. It's a wild, weird and crazy part, in some ways. God knows, it was hard to write. I don't envy her the task of having to perform it, especially at the beginning, when she was trying to find it. What I think is so great about this season is this tremendous cast, and somehow, miraculously, she found this version of Annie that felt compatible with the Annie that we know from the movie and the book, but then really feels entirely her own, as well. That was like a really incredible discovery. One fun thing is that Lizzy had worked with Sam Shaw on Masters of Sex, and during the first season [of Castle Rock], she actually reached out to Sam, to send him a little bit of a fan email. It was at that point that we started talking about, what if we could make Lizzy the biggest fan in the world, Annie Wilkes. So, it was a happy coincidence of a bunch of factors that brought us together, but now it's impossible to imagine having done it without her.

I also absolutely adore Elsie Fisher and think she's fantastic. What did you see in Elsie that made her the perfect counterpart to Lizzy's performance, since that is such an important dynamic to the story?

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Photo by: Dana Starbard/Hulu

THOMASON: Yeah, absolutely. Everyone that I know loves and is obsessed with Eighth Grade, and seeing Elsie in that part was a revelation. When it came time for casting, part of what felt so exciting was the opportunity to put her in a very different kind of role, but one where the incredible vulnerability of this character was gonna be the first thing we saw, and then, by the end of the season, we'd see the incredible strength. As we grow into it, over the first five episodes, we're watching her emerge from her Annie-shaped shell. Part of what feels amazing is that Elsie was really able to embrace the growth. The truth is that Elsie graduated from high school while we were in the middle of shooting. It was really amazing to watch her grow as an actor, and along with that, watch Joy evolve into the character that she becomes, by the end of the season, always with the reflective energy of Annie. The way the two of them play off each other, it does seem like they are locked in an eternal, crazy mother-daughter loop, for all time. That was honestly a happy accident, in that we'd never seen them in anything together, but their chemistry was just so great, right from the first moment.

What made you decide to also bring Ace Merrill into the story, as a character? We know him from Stand By Me, or The Body, and Needful Things. What made you want to bring him in and have him cross paths into Annie's world?

THOMASON: I always felt that, if we were gonna put Annie into a story where there was an even bigger bad, that it was gonna have to be a pretty venerable, bigger bad. We were gonna have to really find someone who deserved to be put into a ring with Annie Wilkes. You'll see the evolution of Ace, over the course of the episodes, but what felt great was the idea that you had these two iconic villains, if you will, and that we could play them off and against each other, and see what kind of explosive combination might result. I've always loved The Body, which became Stand By Me, and Ace also features prominently in Needful Things. He really was the villain that one loved to hate. At some level, even when you look at Randall Flagg, or some of the other villains, there's almost more of a trickster, or they have a cleverness to them. Ace is the bluntest object of a villain that Stephen maybe ever created, and I loved the idea of putting this strange, weirdly formal and sunny disposition Annie villain, up against the blunt instrument, evil incarnate villain of Ace, and seeing what happened.

It's fun that it's not just characters from Stephen King's world, but it's also actors from Stephen King's world. When you bring in somebody like Tim Robbins, who is so iconically known for his work and The Shawshank Redemption, did you need to convince him to jump back into the world of Stephen King, or was he just completely game to be a part of something like this?

THOMASON: Whenever you're talking about actors of the caliber of Sissy [Spacek] and Tim [Robbins], inevitably, no matter what the part is, there's always gonna be a period where you have to really convince them that it's worth their artistic energy. We always start with them, as performers, rather than even the side of their careers that had brushed up against the Stephen King universe. That said, in addition to that, there's always gonna be a little bit of a question, when you're talking about people like Sissy or Tim, who have been in these iconic Stephen King roles, to make sure that the role they're playing here is really different from the one that they were first introduced to the King universe in. That was an appeal for Sissy, and it was also an appeal for Tim. At some level, in this season, Pop is a bad guy. He has some good aspects to him and there's a well-meaning heart beneath it all, but he's kind of a bad guy, and that was exciting for Tim. He wasn't gonna be the heart of gold that Andy Dufresne is in Shawshank. The opportunity to play someone wilder, someone who more integrated into the town, and someone who's more outward with his emotions, frustrations and anger than Andy is, was an important contrast for Tim.

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Photo by: Dana Starbard/Hulu

Is it more challenging to explore already existing Stephen King characters in a new and different way and at a different time in their lives, or is it more challenging to weave new characters that are entirely your invention seamlessly into that world of Stephen King?

THOMASON: They present different challenges. They're both great opportunities, and also can be very hard, at times. With the original characters, you have to really make sure that they feel like they could fit into the universe that Stephen has imagined and created. Whenever you're creating a character from scratch, it's harder, in some ways, because you're always trying to figure out, is this character worthy of the King stories that we know and love, and does this character belong alongside the Mount Rushmore of his iconic heroes and villains. On the other hand, part of what's inevitably challenging about filling in the backstory of a character that is as beloved or behated as Annie, is that you have to make sure you get it right. People have all of these attachments to the Annie that they know and love, so that has its own challenges, both for a writer and for a performer.

Do you already have a plan in place for Season 3? Do you know which characters you'd like to explore next, if that happens?

THOMASON: I could tell you, but then Annie have to ice cream scoop you. Sam and I really tried to map things out broadly, from the beginning, and you'll start to see some of that, as the later episodes come. The plan was always to have an interconnected set of stories and, while every season would be its own launching point, there would be this fabric of Stephen's multi-verse, if you will, that always bubbled beneath it, and a unity to the stories that existed. And so, I think fans of Season 1 will find things in Season 2, that maybe they're not expecting, along the way. And when we get to Season 3, I hope that there will a continuation of what we've done in this season and an expansion, and the audience will start to feel that there was a plan from the beginning.

Castle Rock Season 2 is available to stream at Hulu.