Pretty Little Liars was filled with enough twists and turns to give even the most astute viewers a headache, but the mystery surrounding the show is undoubtedly what kept viewers coming back each and every week. As pieces of the puzzle started coming together, fans started theorizing who could be the elusive "A" that has been tormenting the Liars all these years — and the theories were pretty wild. 

One of the most prevalent theories throughout the show, even after the actual culprits were revealed, was that Aria was somehow involved. A popular Tumblr post provides an extremely detailed breakdown of just how this theory works, and it's hard to argue against. In fact, if we didn't know how it actually did end, we might be first-class passengers on the "Aria is A" train. 

For a time, fans also thought that Lucas, Hanna's friend and former-victim of Alison's bullying, was A. It was even revealed early on that he was helping Mona when she was in charge. Another Tumblr post outlines how it all works. 

Bustle reported on several other plausible theories. They range from speculating that Wren or Ezra is A.D. to the entire thing being a delusion in Aria's head. All of these theories sound insane, but once the evidence is laid out in front of you, it's easy to see how they could potentially work. The endless speculation fueled fan discussions for years as they rewatched the series over and over again trying to pick out the most minuscule details that could provide them with the truth, once and for all. 

As it turns out, they should have been paying more attention to the stars' interviews leading up to the show. According to Entertainment Weekly, Troian Bellisario literally always said, "It's me!" when asked who "A.D." was, but no one believed her.