According to a pretty convincing thebestplltheories Tumblr post arguing that Ali killed Charlotte:

"Alison killed Charlotte. Her begging the liars to say 'I’m not afraid of Charlotte, release her' was all part of her plan to set them up. With all of them saying ‘release her’ and one of them saying 'I won’t feel safe with Charlotte released' it looks like they wanted her released so one of them could kill her — the liars not realizing this is how it sounds at the time of giving their speech... Alison still never forgave Charlotte for all that she did to her, hence she wanted to kill her but had no problem with throwing her friends under the bus for it."

The theory alludes to the fact that Charlotte DiLaurentis' corpse had a rose in its hand, and the fact that we can see these same roses in Alison's house. According to this theory, though, Alison would not be A.D. — this would be a male twin of Charlotte's.

Ready for goosebumps forever? According to a Reddit theory, all the other Liars are dead and Aria is in a mental institution. Reddit user Shipitrealgood references a similar theory from the Pretty Little Puppet Masters Facebook page, which claims:

"... Aria and Alison are the twins from the Halloween story, where one stabbed the other. Aria was then put in Radley where she has been writing a book or maybe just imagining the whole thing and the girls are just representations of Aria's different personalities."

We've seen various outbursts on Aria's part — like when she trashed Ezra's apartment and when she trashed Byron's office — which suggest she might have a darker side, so this isn't the most unlikely theory in the world, especially since Radley orderly Eddie Lamb recognized Aria when she visited, and this was never explained.

Reddit user heftyhannabanana believes that A.D. has been using the characters in the show as board game pawns the whole time. This would explain a lot, including the dollhouse, the board game Mona and Cece were playing with hints about how to get out of Radley, and Sara bringing the Liars into a room for Charlotte revealing herself to be A.

This has been huge for years, but the "Spencer has a twin" theory gained traction after the Season 7 premiere, in which "Spencer" appears to Hanna in a dream to give her comfort (Hanna has been kidnapped). But she doesn't have bangs (as Spencer does), and she refers to the new A character as A.D. (and this is prior to the other Liars receiving their first text in which A.D. signs off as such). Just as the last big "ending" revolved around us discovering Ali had a sibling we didn't know about, could this mirror the last big reveal with Spencer's twin tying up all the loose ends?

In The Outlast's theory on Tumblr, they argue that the twin would be Bethany Young. This makes sense, since we've never seen Young's face as an adult, and in Episode 8 of Season 7, Dr. Cochran reports that he delivered "two of her babies" while Mary Drake was a patient in Radley. They argue that Charlotte killed Marion, not Bethany, and Bethany's murder of Charlotte is in retaliation for this.

As Bustle writer Kaitlin Reilly has pointed out, Mona could be A.D. simply because she never got what she really wanted from the original game; she's no closer to getting Hanna back from the Liars. Reilly points out that Mona knew the Liars had killed Dr. Rollins:

"...and offered to cover up the crime — which means she's also the one who could have, theoretically, led the cops away from the trail. She also was supposed to be watching Noel Kahn when he got out to go to the PLL death trap in the Season 7A finale — could Mona have orchestrated everything that happened in the house?"

Any ending that involves Mona would be explosive. Given that she's always proved she's smarter than the Liars, arguably this could be the darkest possible timeline, ending in one or more deaths of our five leads.

As Reddit user SamanthaShearer points out, Wilden might not be dead. After all, we thought we saw Mona's corpse, but she still turned out to be alive. She suggests other weird stuff that doesn't quite add up: a figure at Wilden's funeral who resembled him, the fact that Archer Rollins impersonated Wilden to scare Alison, and the fact that A.D. had a policeman outfit to hand to attack Alison in her bedroom. She argues that Wilden could even be one of Mary Drake's children and CeCe's twin.

As PopSugar has observed, Wren could be A.D. because there are a lot of clues which suggest he's in the medical profession ("Everything from medical supplies to prescription pads to medical records have come into play. And let's not forget the Dollhouse, where the girls find themselves surgically implanted with trackers."). There's also the fact that he theoretically knew all about Mary Drake long before we knew she existed; in a scene in which he appears to be coloring in Redcoat, he colors the hair black so she resembles Spencer's mother and states "Just goes to show, you can't trust anyone."

Is Charlotte really dead on Pretty Little Liars? Bustle writer Lindsay Denninger doesn't believe so, arguing the character has a history of disappearances and that Rosewood isn't safe for her. She suggests that since neither Aria nor Ezra were comfortable with Charlotte being in the town, that they may have helped her escape.

This potential ending is strengthened by the fact that the list of stunt doubles for the final episode shown on IMDb includes one for Charlotte (Vanessa Rey), suggesting that either there's a flashback scene... or she's still alive.

There's even a website with every single hint from each episode that Aria is A.D. But major clues include the fact that everything A-related first began when Aria returned from Iceland (or possibly even a year in Radley), the fact that Mona refers to her as "Big A" in the second season, the way she styles the second "A" in Aria when she writes her name on the train window in the Season 3 Halloween episode, and way, way more. This is also supported by the fact that Keegan Allen (who plays Toby) told People of the ultimate A reveal:

“Everyone will freak out because it’s so clearly in every episode. When it’s finally revealed, you could literally go back to season 1 and knowing who it is, you can be like, ‘Oh, wow. Whoa. This has been here all along, and I never noticed it,’ which is, I think, brilliant.”

So presumably it has to be someone who's been there all along... someone like Aria.

This thebestplltheories Tumblr post argues that Jessica DiLaurentis is alive and Mary Drake is dead. We're not the only ones who witness Charlotte walloping Ali over the head with a rock; Jessica sees this too. So why does Charlotte keep calling her "mom" over and over? Maybe because it wasn't Jessica who witnessed the act of violence, but Mary. Which means Mary was the one who buried Alison. The theory argues that Jessica killed Mary in Season 4, Episode 24, given that when CeCe finds the body, she cries “mum, mommy, you can’t leave me!”

If this was proved to be the case, I'm calling it: Either Ali or Spencer would end the show back in a mental institution.

According to Reddit user dena_is_a, there's a ton of evidence to suggest that the endgame is us discovering that Ezra is A.D., and that he's also Charles' twin / older brother. They note that Mona would have needed help to move Ian's body, that "nothing bad ever happened to Ezra during Mona's reign," the suspicious number of business trips he took around the time that CeCe was out of the country, his lair, the flimsiness of a grown man hanging out with a bunch of 16-year-olds simply to write a book, and the lack of bad things that happen to Aria and Ezra.

There's further evidence not cited in the theory — the name change, his ability to keep a secret for years and years (as he did with his and Aria's relationship), the moments where he abruptly loses his temper. Again, this could lead to a seriously dark ending, depending on whether the discovery is made prior to or following the Ezria wedding.

In the words of Bustle writer Kaitlin Reilly, "Lucas is essentially a free agent with unlimited funds — who would notice if he spent his time and money torturing the girls?" So is Lucas A.D.? Reilly makes some other excellent points, too. There was the time his house almost killed Aria, there was the sketchiness of his offering Hanna a free flat to crash in, and the fact that he's perennially in Rosewood even when he's meant to be traveling. Plus, the fact that he's an app developer and the whole board game aspect of things.

If Lucas is A.D., I imagine the ending will pit the two smartest people in Rosewood against each other: Mona and Lucas. And that one of them won't survive. Because if Lucas is evil and Mona keys back into the dark energy she had as the first A, then neither of them are going to back down.

Wiki user Champagne Lady posted a spoiler from Reddit from someone who claimed to work on the show claiming that Paige is A.D.. Given that a lot of their predictions have already come true, this leads me to conclude that they may actually be an insider (or at least talented at guessing) and as such, their guess could be more informed than most.

"Uber A is Paige. She is Mary Drake's second child and she is trying to avenge her sister, Charlotte. Paige has been involved all along and she was the real redcoat and the one who really stole the game from Mona. Marlene lied a lot in her interview after 6x10 and Paige really killed Ian, Garrett, and Wilden although her motives for those deaths are not explained in 7x20."

It also clarifies that Melissa killed Charlotte, not Paige:

"Melissa killed Charlotte with her suitcase handle as the Liars previously suspected. Her motive is a combination of revenge on Cece and protection for Spencer."

What would this mean for an ending? Arguably this would be one of the happier endings, since Paige isn't a key member of the Liars' friendship group (as Aria or Ali are, for example); she isn't anyone the Liars are currently dating and, in fact, her being Uber A would just bring Emison closer together.

Pretty Little Liars has woven a tangled web all these years, and they're going to need to do some narrative gymnastics to tie up these loose ends. Only one thing's for sure: The ending won't disappoint.