Warning: This story contains mild spoilers for episode 6 of Pretty Little Liars: Original Sin.

The Pretty Little Liars and Riverdale universes are one and the same. In a recent episode of the new spinoff series Pretty Little Liars: Original Sin, the new Liars pay a visit to Rosewood, the location where the original series took place. They learn that several patients from the local sanitarium had been “sent to the Sisters of Quiet Mercy over in Riverdale.” That’s a clear reference to The CW’s Riverdale in which the Sisters of Quiet Mercy is featured as a home for troubled youths and parentless children.

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While he was not involved with the original series, Pretty Little Liars: Original Sin was developed by Riverdale creator Roberto Aguirre-Sacasa. In a new interview with TVLine, Aguirre-Sacasa, who also serves as executive producer and showrunner on Original Sin, has confirmed that the Riverdale reference was an acknowledgment that these two shows are part of the same universe. As Aguirre-Sacasa explains:

If the Pretty Little Liars and Riverdale worlds are now linked, does that mean there could be more crossovers to see in the future? Aguirre-Sacasa is certainly open to it, as is at least one cast member who’s also pushing for a rivalry between each show’s respective local sports teams. But while Aguirre-Sacasa would love to mix these shows a bit more, he can’t guarantee anything, as any plans could always potentially get vetoed by The CW or HBO Max.

Linking the Universes Creates a Continuity Error

It’s interesting to think about Pretty Little Liars: Original Sin and Riverdale sharing a universe, as, by extension, each show’s respective spinoffs are also included. The original Pretty Little Liars and its previous spinoffs, Ravenswood and The Perfectionists, would be included. The same can be said for the Riverdale universe shows, Chilling Adventures of Sabrina and the short-lived Katy Keene.

Here’s where things get tricky, as Lucy Hale plays main roles in both Pretty Little Liars and Katy Keene. Secret twins are not all that uncommon in the Pretty Little Liars universe, so is that the case with Aria and Katy? Or do the two just happen to look exactly alike? In any case, executive producer Lindsay Calhoon enjoys imagining Hale playing both characters, however they want to explain it.

You can find Pretty Little Liars: Original Sin streaming on HBO Max.