'Pretty Little Liars: The Perfectionists': How Alison and Mona Come Together in 'Darker' Spinoff (Exclusive)

Sasha Pieterse is spilling brand new details all about the potential spinoff series – and we’re living for all this new info!

It's official! Pretty Little Liars: The Perfectionists has been picked up for a 10-episode first season at Freeform. 

On Friday, star Sasha Pieterse spilled brand new details about the new series – and we are living for all the latest info.

When PLL ended, Mona had headed to Paris – and was still seemingly playing a game of her own. She and Alison we’re definitely not close pals throughout the series, but Pieterse says that changes in their new town, Beacon Heights.

“When I read the draft that we were going to film, I cracked up in so many spots because of the way that they tie in their two characters,” the actress told ET during our live interview. “They kind of become allies in a way and it’s this very interesting kind of dynamic, 'cause Alison’s obviously not sure if she can trust Mona. I mean, can you ever trust Mona? But the way that she ends up being in this new town is very mysterious, but also hilarious, the way that she kind of rides over these questions,” she explained.  

“I think the fans will appreciate the mystery there, there’s enough told that, you know, ‘OK, we’ll find out,’ but a hilarious way of Mona putting it across, so…yeah, it’ll be good," she added.

Interesting. Ali and Mona as allies? We already love it. 

Pieterse also thinks the show is somewhat creepier than PLL

“It’s definitely darker than how our first season of PLL was,” she said. “I feel like it picks up from PLL kind of seamlessly, there’s a two-year gap, yeah, and it just.. it will be darker, let me put it that way.”

Alison will still be teaching this time around, too. 

“Yes! I feel very official… blazers and, like, it's very high-tech in Beacon Heights, which I really appreciate, just like, ‘Oh, I’m fancy.’” 

And it’s not just the more mature wardrobe Pieterse is excited about -- she’s ready to explore a more grown-up side of Alison. 

“I really loved seeing Alison’s character grow and part of it is also that you can’t make me a teenager anymore, you can't do it!” she joked. 

“That’s kind of a fun, terrible thing to say, but I feel like we played teenagers so much that it was really so nice to kind of be this adult figure... it was like flipping the tables,” she added. “It was such an interesting perspective and way of exploring Alison’s adult side and how she’s dealt with this space that you haven't seen yet, and there's so much room for her to grow and for the fans to explore, which I love, and you meet these wonderful, well-rounded characters and I think the fans will definitely, if they get the chance, fall in love with these new people and their struggles and their lifestyle and I think you can relate to it.” 

Alison is of course mother to twins with Emily (Shay Mitchell), but Pieterse stayed mum on whether those babies appear in the pilot.  

“I don’t think I can reveal that! The twins are very awesome, but I think [creator/showrunner] Marlene [King] would get mad and I also don’t wanna get fired before I start!” she joked. 

She also couldn’t reveal whether Emily or any of the other little liars make cameos in the pilot. 

“I cannot say that… it’s not a no, but it’s not a yes,” she teased.

Don’t fret, though. Pieterse previously told ET that they didn’t think getting former cast members to appear would be an issue. 

“I'm sure that they will,” Pieterse teased last fall. “We have to keep the PLL family alive, obviously -- and Emison, of course. I don't think that will be a problem at all. I think the fans will really appreciate it, so that's what we really care about anyway.” 

”Marlene just really likes to keep it in the family, literally," Pieterse added at the time. "She's such an amazing person. She's got such a big heart and we really love her so much, and the fact that we can all stick together somehow, really means a lot to us.”

Pieterse, who currently stars in the new flick, The Honor List, also revealed that one of her co-stars in the film, Chris Mason, was cast in The Perfectionists – and she may have helped with that. 

“I emailed our casting director and I was like, 'You have to hire him immediately,' and he was the last character we cast and we just had a ball,” she gushed. 

But, like us, Pieterse hasn’t seen the pilot yet. 

"No! it's not fair! I feel like, well, the cast is usually the last people to see it, obviously before the fans see it, but I’m dying to see it,” she exclaimed. 

Us too, girl, us too. 

For more from Pieterse, check out the video above and below.