The franchise’s newest chapter, Pretty Little Liars: Original Sin, arrives on HBO Max July 28.
And it had, at the beginning, an anonymous narrator," Morgenstein tells EW.
And that character became ‘A,’ in the books."

‘Pretty Little Liars’.
Drawing from her own life, she then started to build out what would become Rosewood.
“I grew up outside Philadelphia and everybody seemed perfect.
“The main characters were based on me at different times of my life growing up.”

Lucy Hale, Shay Mitchell, Ashley Benson, Sasha Pieterse, and Troian Bellisario.Freeform
Hanna was the junior high version of Shepard, desperate for popularity.
Emily represented when she got into swimming and found a loyal group of friends.
Aria was her artsy phase, when she was “completely over the little town where I lived.”

Zaria, Malia Pyles, Maia Reficco, Chandler Kinney, and Bailee Madison on ‘Pretty Little Liars: Original Sin’.Karolina Wojtasik/HBO Max
And then, as Shepard puts it, “I was always Spencer.”
They asked her for another four.
But the process wasn’t as straightforward as fans might think.
“Once we sold the books, we sold development to the WB,” Morgenstein recalls.
“And we stumbled through TV development a few times with a few different writers.
There was a version that was YA teen but departed from the books.
There was a version that was adult characters.
Because in the intervening years of stumbling around in TV development, the books became a big hit.”
As thePLLfandom grew, so did social media.
But whenThe Perfectionistsdidn’t garner the same popularity as the flagship series, it ended after one season.
Much like many ofPLL’s antagonists, the franchise doesn’t like to stay dead for long.
But don’t worry, they’ve done their research on the original.
And for Bring, the project is particularly personal.
“I lived right next to Warner Brothers in this little apartment for 10 years,” Bring says.
Every day, I’d hear, ‘Are you ready to go to Rosewood?’
So, hilariously, the gateway intoPLLwas living by Rosewood.”
But Aguirre-Sacasa and Bring knew that they needed to bring something different to thePLLworld.
After all, this wasn’t a remake.
“One of the things Roberto and I both loved from working onSabrinatogether was horror,” Bring says.
“There were so many greatPLLtropes that Marlene and her writers and those actors executed.
So it was a rolling conversation about how much to honor and include,” Aguirre-Sacasa says.
“The production value is higher than the original series,” Morgenstein says.
“It all feels a little more grown up.
It’s a tonal departure.
I think it delivers.”
“That’s never going to go away.
Plus, as she adds, “Everybody has secrets.”
Pretty Little Liars: Original Sinpremieres July 28 on HBO Max.