Pretty Little Liars has been dropping hints that Alison DiLaurentis (Sasha Pieterse)  has a twin since Day One. At first, the twin theory seemed implausible crazy speculation that had no actual base in PLL reality but that’s not the case anymore. The possibility that Ali has (or had) a genetic doppelganger walking around Rosewood is making more and more sense. Here are five reasons why we think it’s very possible Ali has/had a twin.

Ali’s (autobiographical?) twin story

Though Ali sometimes played ignorant, she was actually smart really smart. Much of what she said had double-meaning, an inside joke that only she understood. We think this was the case with the killer-twin story she told a boy she was babysitting in the Season 2 Halloween flashback episode. In the story, one twin stabs the other over a doll, and is promptly sent to an insane asylum. We think this story much like everything that came out of Ali’s mouth had a hidden truth to it. In fact, we think it was her own childhood story. The only question is: which twin was she?

The body vs. the sightings

The reason everyone in Rosewood seems to be convinced that Ali is, in fact dead, is because her body was found. However, this doesn’t match up with the number of Ali sighting we’ve seen since her “death,” nor the story Mrs. Grunwald told the Liars about pulling Ali from the ground the night of her supposed death. Either the coroner is lying, the many people who have seen Ali, or there are two of them. We actually think a twin theory makes the most sense.

DiLaurentis home decor

Most of the “evidence” we have for our twin theory is highly circumstantial. The closest we get to cold hard evidence are the photos seen hanging on the walls of the DiLaurentis home. There are numerous framed photos that hint at DiLaurentis twins, including a frame with a picture of Jason and seemingly two photos of Ali (or, in our speculation, one photo of Ali and one photo of her twin). There’s also a decorative plaque seen hanging in Ali’s room in a flashback that reads (in French): “This is the double laugh, the double smile, and double the trouble if you’re blessed with twins.”  

The books

Pretty Little Liars the TV show is very much its own narrative, separate from the story told in the book series but the former is obviously inspired by the latter. The Liars. Rosewood. “A.” Ali’s “murder.” These are all plot elements drawn from the books. One of the crucial plot twists of the book series comes when readers discover that Ali had a twin, Courtney, who was a patient at Radley. Courtney manages to switch places with Ali, and it is she who becomes friends with the Liars. Ali eventually breaks out of Radley and kills Courtney for taking her place. We doubt the series will follow this plot closely, but we could definitely see it drawing on the twin premise more generally.

Ali’s bi-polar behavior

The twin theory also explains a lot about Ali’s seemingly bi-polar behavior. At times, she is a sweet, loyal friend who though always somewhat manipulative obviously loves the Liars. Other times, she blackmails them into doing what she wants, threatening to expose their secrets. This behavior could belong to one, unstable person or it could be two separate people with two separate personalities. Our money is on the latter.

Do you think Ali has a twin? Share your evidence for why or why not in the comments below!

Catch the Pretty Little Liars Season 4 Halloween special on Tuesday, October 22, 2013 at 8 p.m. ET on ABC Family.