One of the best parts about watching Pretty Little Liars is all the mystery. Who is Uber A? Who is Mary's secret child? Who killed Charlotte? So many questions, so little answers. That's where theories step in. We hypothesize and make deductions like we're Spencer Hastings who happens to be one of the most popular characters to theorize about. And trust me, there are a lot of Spencer theories for Pretty Little Liars. At the moment, Spencer might be the most theorized Liar on the show, which could or could not mean she's actually involved in something.

Throughout the seasons, Spencer has always been the cool, calm, and collected one. She thinks before she acts and is always very calculated. But is she too calculated? Ones got to ask, is there a possibility that Spencer is somehow involved in the Uber A plan? Or is she at least involved in something? Fans on Reddit and forums are definitely looking at the younger Hastings for clues about what type of reveal is to come. But what exactly are the theories?

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Based on the twin twist in the Pretty Little Liars novels, fans have been looking for the twin twist in the show. Although we already got one with the whole Mary/Jessica thing, some fans still believe it could be one of the Liars that has a secret twin. Reddit user CeCeIsNotCharles theorizes that Spencer has a secret twin who is now pretending to be the real Spencer in Rosewood and that both girls are Mary Drake's daughters. The idea is that while one Spencer is working with the Liars, the other Spencer is working against them as A.D. This theory may sound a little crazy, but this is Pretty Little Liars so everything's a little crazy.

Spencer Killed Mary's Secret Child

If you read the Pretty Little Liars novels you know there was a brief period where Spencer believed she killed Ali. Her memories about the night Ali went missing were messy at best, but she believed that she may have killed Ali but repressed the memory. Of course it turned out that wasn't true, but it seems like the PLL writers may be bringing this idea into the show. In the promo for Tuesday's episode, we see Spencer watching a video of herself in the dollhouse that A kept them in.

While in the dollhouse Spencer freaked out about having blood all over her, but in the video there's no blood on her at all. This may be A's attempt to convince Spencer she's crazy. However, some fans believe that the reason Spencer imagined blood on her hands is because she has a repressed memory of killing someone in the past, presumably Mary's other unknown child. Alternately, fans also pointed out that Spencer looks to have bangs in the video, so maybe A really is Spencer's long lost sister and she's trying to tell her something with that video. Either way, the video is suspicious.

Spencer Killed Mrs. DiLaurentis

Apparently we all believe Spencer's capable of murder and who knows, maybe she is. Following along the same lines about a repressed memory, this theory has a little more merit because Spencer was hopped out on drugs around the time Mrs. DiLaurentis was killed. Add in the fact that Mrs. D was found in Spencer's garden, it's not a big leap to think Spencer killed Mrs. D. However, the timeline of Mrs. D's death is a bit difficult to follow, and it's very likely that Spencer was in New York with the rest of the Liars when Mrs. D was killed. Still, the idea that Spencer might've killed Mrs. D and then repressed the memory is a popular theory that will hopefully either be proven or disproven soon. Seriously, can the Rosewood P.D. at least solve one murder?

Spencer is A.D./Uber A

There's so many different theories about why Spencer could be A.D., but the fact is many fans believe it's Spencer that's been pulling the strings this whole time. If Spencer is Mary's secret child, it would make sense why she would want to find out who killed Charlotte. But why would she continue to work with the Liars if that's the case? Although it would be an awesome twist to discover Spencer has been A.D. this whole time, it just doesn't seem to make much sense.

With all these theories any one of them could be true — or none of them at all. We'll just have to wait and see how this all plays out. At this point everyone in Rosewood is a suspect and the Liars should trust no one, not even each other.