From Roberto Aguirre-Sacasa and Lindsay Calhoon Bring, the 10-episode HBO Max drama series Pretty Little Liars: Original Sin follows a group of teen girls – Imogen (Bailee Madison), Tabby (Chandler Kinney), Faran (Zaria), Mouse (Malia Pyles) and Noa (Maia Reficco) – being forced to answer for the sins of their mothers in a way that finds them in a nightmare straight out of a horror movie. Tormented by an unknown figure that goes only by “A,” they band together to not only uncover the secrets and lies plaguing them, but also to get to the bottom of just what happened 20 years ago.

During this interview with Collider, co-creators/writers Aguirre-Sacasa and Calhoon Bring talked about how this series came about, finding their own take within this world, what it’s been like to put this cast together and watch them work, developing the look of the killer, how far ahead they’ve thought about the story they want to tell, whether they know who A is, and the freedom of not having to deal with network standards and practices. Aguirre-Sacasa also talked about the unexpected journey he’s taken with Riverdale, and how excited he is to show fans what’s in store for the final season.

Collider: Roberto, you’ve worked with source material with the Archie comics for Riverdale. You’ve reinvented a TV series with Sabrina. Now, you’ve created this new chapter of Pretty Little Liars with Original Sin. What made you want to do this series and what is the fun for you, in reinventing these things that existed already, but in very different forms?

ROBERTO AGUIRRE-SACASA: It’s funny, that is true, with very different circumstances. My bosses at Warner Bros. reached out to me and said, “Hey, what do you think about doing a new version of Pretty Little Liars?” Very candidly, I knew what PLL was. It was a huge pop culture juggernaut and a defining YA show for in television. When I was working on Riverdale, I watched every YA pilot, like My So-Called Life, Dawson’s Creek, Everwood, and Pretty Little Liars was one of them, so I knew it from that. But I went back and watched more episodes and was like, “Yeah, I get why they’re asking me to do this.” But unlike Riverdale, and even Sabrina, though Sabrina was centered on Sabrina and that was a very female-centric show, Pretty Little Liars, at its core, was about the friendship of these five girls, and about their experiences coming of age and moving through the world. I very quickly knew that I needed to partner with someone who could speak more authentically and channel more authentically the experiences of teenage girls.

The reason we’re all here is that Lindsay Calhoon Bring] knocked on my office door. After I had asked the Riverdale, Sabrina, and Katy Keene writers’ room, if there was any writer who would be up for maybe figuring out a new way to crack a new PLL story, Lindsay showed up at my office. It’s been such a great partnership. Like Lindsay, I’m a huge horror and slasher fan. We worked on Sabrina, which had so many horror elements, but one thing I hadn’t done was a full-blown slasher/horror show with a villain like Michael Myers or Jason or Freddie Kruger. We’ve flirted with that, but hadn’t ever really done it. Doing a slasher show, like Scream, I Know What You Did Last Summer, My Bloody Valentine, April Fool’s Day, Prom Night, and all of these movies from my youth, got me really excited. And then, Lindsay zeroed in on and tapped into who these girls are and would be, and what they were struggling with. Then, I was like, “Oh, this is great.”

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Image via HBO Max

Lindsay, what’s it like to take on a show that had such success and the cast was so iconic, and feel like you saw something in that, that made you feel like you could add to it? Is it terrifying to realize that, is it exciting, or is it both of those things?

LINDSAY CALHOON BRING: I think it was equally nerve-wracking and exciting. Part of that is that so much of the joy, for me too, was collaborating with Roberto. Knowing how Roberto’s mind works, in breaking story and character, and that there’s no substitute for great story and great character, I felt very safe collaborating with Roberto because I knew that we would make something special. I knew that Roberto would not rest until we felt amazing about the show, amazing about the characters, and amazing about the stories, and that I could learn so much from that experience. It was daunting, in the sense that it’s such a huge title, it has such a rabbit fan base, and people love the show, but Roberto and I love the show too. We were really wanting to pave the way, and make something new and special while still honoring the original. I do think and hope that we did that, and that we service the original in a way that it exists and is untouched perfectly in Rosewood, a couple of towns over, and we’ve expanded on the universe. It’s scary, for sure, but now on the other side of it, I’m feeling very excited and very proud of the show that we made, and just want to share it with everybody. I’m really hoping people will love it. They have every reason to, with the cast in our show. Our cast is special and amazing, and they’re just wonderful people and wonderful actors. I think everyone’s gonna love them.

The original series was successful and the cast became iconic, and Roberto, you’ve also done that with Riverdale and that cast. What was it like to find this cast, and what makes this cast special? What has most impressed you, from spending the season working with them, seeing how they work, and watching all of that develop?

AGUIRRE-SACASA: In casting the pilot, we work with the brilliant casting directors, David Rapaport and Lyndsey Baldasare, and they’ve brought together such incredible casts over the years. You’re right, with the original PLL show, all of those actresses were stars and iconic. We knew that we needed to try to find a really special, unique group of actors. We cast everybody via Zoom because it was during one of the heights of the pandemic, and with every single one of the actors we cast, Lindsay and I would text frantically and be like, “That’s her!” We did Zoom chemistry reads, which are brutal, but they were so right for the roles that they came through, even then. One of the first, or maybe the first PLL that we cast was Maya Reficco, as Noa. She had this incredible fire in her and was so passionate. It was incredible. What’s been the most fun is that, over the 10 episodes, and some of these actors have been acting since they were three while some were much greener, we’ve gotten to see them gel as a unit. From episode one to episode 10, the way that those actors worked together was incredible. They were so dialed in. That trajectory has been really fun to see. There was one scene in the pilot that we ended up reshooting because the story changed a little bit, and even a month later, shooting that scene compared to when we shot it during the first week of shooting, it was like, “Oh, my God, these girls knew their characters so well.” They came in, and it was like night and day. That has been really fun.

CALHOON BRING: Friend love is real love. I think our love story of the show really is these girls becoming friends, and that’s happening on screen and behind the scenes, in a really, really beautiful way. They’re just so connected and so supportive of each other. It’s amazing to see and watch, as the season progresses.

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Image via HBO Max

This show leans quite a bit into horror and suspense, especially having a nameless and faceless figure running around, and masks on killers in horror are very iconic. How did you come up with the look for this scary figure, having his body covered, wearing gloves and not seeing his face? How did you want to represent that and figure out the look?

AGUIRRE-SACASA: I won’t be happy until there is a custom action figure of A. We’ve gotta give full credit to our brilliant director, Lisa Soper. Lisa is a brilliant designer and a brilliant production designer. In the original script of the pilot, we described A as wearing an animal mask, like a jackal or something. Once Lisa came on board as director, we called her up and were like, “Do you wanna take a crack at what the mask is? Forget what’s in the script. See what inspires you.” I think Lisa stayed up all night, and the next day, she sent us 10 or 12 sketches. There were a couple of animal ones, but we were like, “Well, that’s not right.” And then, I think the last one was the earliest version of what’s in the show, which was a terrifying, stitched together horror mask that was like a little bit like Michael Myers, a lot like Leatherface, and like something out of Silence of the Lambs. It was just so creepy and horrifying. And then, from there, we worked with our costume designer to come up with a Michael Myers, generic, creepy janitor jumpsuit.

I love that you even play with putting him in a Halloween mask for the holiday and shooting some of that episode through the eye holes of the mask.

AGUIRRE-SACASA: I love that episode. I love that set piece. It’s so good.

CALHOON BRING: I love the idea that a masked villain could hide in plain sight on Halloween night, by merely wearing another mask. That’s so fun. I love that, too.

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Image via HBO

Roberto, you’ve taken a long wild road, from where Riverdale started to where the show will be ending up. With all the crazy things that show has done, did you know that the end point you would eventually get to would be this end point? Is where you’re headed where you always thought you’d be headed, or are you surprised?

AGUIRRE-SACASA: I’ll be honest with you, no, I don’t think anyone knew that. I would be lying if I said I ever imagined that Riverdale would be getting to Season 7, but I’m really excited about Season 7. And though it is not what I originally imagined, it’s perfect. It’s totally surprising, and yet completely inevitable, so I’m really excited. But no, I’m not gonna lie, I had an idea for where it was gonna end, and we were going there, but then, when we were wrapping up Season 6 and having conversations about Season 7, a new idea came in that we’re really excited about.

I’m always so curious because I talk to a lot of showrunners, creators, and writers, some of whom say they know exactly how their show will end while some say they have no idea, or a general idea.

AGUIRRE-SACASA: They’ll say, “I know the exact image.”

Even with Pretty Little Liars: Original Sin, how far ahead have you thought about the story you’d like to tell?

CALHOON BRING: It’s funny, even with this show, in Season 1, you always get on the train where the story is headed. Even if you have an idea, Roberto’s philosophy, which I love and have learned from, is that the best idea wins and the best story wins. If there’s a direction we thought we were headed, but a better story rears its head, you go with that better story. There are some things in Season 1 that we strangely stuck to, from the beginning, from the pitch, like some of our mysteries. And then, there are some things that certainly evolved over the course of the season and changed. We do have ideas for moving forward, and we have some pretty fun and exciting story ideas and places for the characters to go after this.

Do you guys have a very clear idea of who A is?

CALHOON BRING: Yes, very much so.

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Image via HBO Max

What are the challenges, and what is the fun of having twins as part of the story you’re telling? Were there specific things you wanted to explore with that?

AGUIRRE-SACASA: Twins have always been such a staple of the horror genre. There are the Grady twins in The Shining. Carrie very famously has twins in it. There’s just something uncanny about twins that we love. This honestly came out of this incredible actor who came in and read Karen. We got really excited about that, and it was one more mystery to lay into the show. Actually, one of my favorite things about Season 1 is the very unlikely friendship between Kelly, if it’s Kelly and not Karen, and Faran. I love that storyline. It’s something that continues to the end [of the season], and I think it’s really satisfying. Buy yeah, twins are great. In terms of challenges, it’s tricky. We had Kiernan [Shipka] playing twin Sabrinas for about a year and a half, and one of our ADs worked on The Deuce, which has a lot of twin work, with James Franco playing two characters. We were ready for it.

CALHOON BRING: I also wanna give love to Mallory Bechtel, who plays Karen and Kelly. She’s such a special actor. She really does have a method to her madness, in everything. She would show up to set in a very different mindset, when she played Kelly versus Karen. She had a different way that she held herself and a different way that she would speak. She was so thoughtful about that. Early on, seeing her performance and seeing how talented she is, that did inspire more story and more to give Kelly, which was really fun.

How has doing this for HBO Max affected the content and the material that you can explore? I love the fact that you have teenagers that can use language that you might not have been able to use, who would absolutely use that language to react to these situations.

AGUIRRE-SACASA: Yeah, definitely. I know that it is hugely frustrating for the Riverdale cast, when they have to say, “I’m sick of this crap,” or “That friggin’ sucks.” I don’t know how many times KJ [Apa] has called me and said, “I’m not saying friggin’.” And I’m like, “What do you wanna do? What can we do?” What I’ll say about it is that I don’t think either of us is into gratuitous violence, gratuitous sex or nudity, or gratuitous language. That said, all of those are part of the horror genre, so having the freedom to include that stuff is great. But it’s never about that. We’re not like, “Oh, my God, we’re on HBO Max, so we’re gonna have a lot of nudity.” It’s more like, “Does it serve the character? Does it serve the story? Is there a way to include this, that is true and real, but not exploitative?” Those were the thought. But it’s hard to do a horror show, on a network with network standards and practices, for sure.

Pretty Little Liars: Original Sin is available to stream at HBO Max.