This post contains spoilers for the finale of Pretty Little Liars.

Now that we know that A.D. stands for Alex Drake, it's almost impossible to imagine any other character fulfilling the role of Rosewood's ultimate stalker/sociopath so chillingly. But even though showrunner I. Marlene King dreamed up Twincer as early as season five, Spencer's evil twin wasn't the first idea she had.

"Originally my mind was going to Wren as A.D., but we had to be realistic and there have been times when we really needed a character who wasn't a series regular and we couldn't get them on the show," Marlene explained to Entertainment Weekly.

Note: Only on PLL could a long-lost, secret, evil, British twin torturing and impersonating her American sister out of jealousy be the MORE "realistic" option.

ABC

"The show is so deeply rooted in mythology and I've always said you have to know the ending before you know the beginning or else it won't make sense, so that dictated that we needed to make A.D. someone who was a series regular," Marlene continued.

Wren is portrayed by actor Julian Morris, who always guest-starred on the show and was never a series regular.

So instead, Marlene opted for a cast member who was always on set, and added the twin twist to avoid messing up the tight bonds the Liars all share with each other.

"I know a lot of fans wanted it to be one of the Pretty Little Liars, but I could never justify that being true because the show was always about their unconditional friendship," she said. "That then sort of led to this idea of, well, if we make it a twin of one of the Pretty Little Liars, that's sort of like making it a PLL, but ultimately, it makes more sense."

I mean, "sense" is kind of a hazy concept in Rosewood, but I get what she's saying!

Hannah Orenstein is the assistant features editor at Seventeen.com. Follow her on Twitter and Instagram!

This content is created and maintained by a third party, and imported onto this page to help users provide their email addresses. You may be able to find more information about this and similar content at piano.io