Red Coat

"I did everything you've asked me to."

- Mona to Big A

Big "A", also known as the Main "A", Head A, or simply the "leader of the A-Team", is an unknown character responsible for the creation of "A" and the A-Team. Little information is known about this person, who only makes appearances wearing a red trench coat. Big "A" is considered to be the main "A" and the leader of the A-Team, as she is the one calling the shots, and telling her workers (aka minor "A's") what to do (such as ordering Toby to steal Alison's body and ordering the deaths of Ian Thomas and Garrett Reynolds). Though this character is considered to be the main "A," she has little to no physical  involvement with the Liars since she orders her team members to actually do the things that A has been known to do to the liars.

It is possible that Mona was talking to Big "A" in "The Lady Killer", as it was clearly shown that Mona was taking orders from someone when she said: "I understand" on the phone.

While the A-Team members are known to wear a black hoodie, black gloves and black pants, Big "A" makes her appearance in a red trench coat or a red hoodie.

In "Misery Loves Company," it's revealed by Mona that the leader is a girl.

The Beginning
A has gone into business since Halloween 2008, when she began tormenting Alison DiLaurentis, at the time unbeknowst to the liars. When the episode premiered, it was mostly unknown to the audience that A was in fact a team of people. Most likely, Big "A" was responsible for the creation of A and the A-Team, and that members such as Mona Vanderwaal and Toby Cavanaugh were recruited later on.

Season 2
In the Season 2 finale of "UnmAsked," it has been revealed that Mona is in fact A. After Mona knocks Spencer Hastings unconscious and puts her in her car, Mona gives Spencer an "offer she can't refuse": either join the A-Team, or die! After the fiasco on Lookout Point, and when Mona is taken to the police station before departing for Radley, she says in a monologue: "They think it's over! Loser Mona's going to the nuthouse and those precious liars think they can sleep with their windows open and their doors unlocked . Don't they know that's what we want!" It now becomes confirmed at this point that A is a team of people.

At the end of "UnmAsked," we see Mona sitting in her bed at the Radley Sanitarium. A visitor wearing a red trench coat, much similar to that of Vivian Darkbloom, stands before Mona, to whom she says: "I did everything you've asked me to!" It is highly implied that this is the Big "A", and that he/she is the main "A" and the leader of the A team (who calls the shots and controls their workers/minor A's). It becomes quite clear that though Mona is part of the A-Team, and has physically done everything that "A" has done to the Liars, she is simply working for the Big "A", who tells her what to do (hitting Hanna with a car, and other things).

Season 3
By Season 3, it is officially confirmed that A is a team of people: the A-Team, and that due to the ending scene of the Season 2 finale, this team is controlled by the main A: Big "A", who calls the shots.

In the second episode of season 3, Blood Is The New Black, we see Big "A" once more. Wearing a red hoodie, she is seen buying black hoodies and gloves for her workers. The store owner says to Big "A": "So, are you buying this for a team?".

Throughout season 3, there is a "New A" tormenting the Liars. In The Lady Killer, it is revealed that Toby is this "A," and is also part of the A-Team! The dramatic irony is that the Liars don't seem to understand that both Mona, and the New A, are simply workers for the Big "A". In the same episode, we also see Mona possibly talking to the Big "A" on the phone since Mona learns from the other person that there is a "change of plans". Since Big "A" is usually the one planning out all of the "A" schemes, it seems as if it really was her.

It is obvious at this point that there are much more A-Team members then just Toby and Mona.

In Misery Loves Company, when Hanna goes to the boutique, she sees in the window reflection a blond girl wearing a red coat (the same color as Vivian's jacket) across the street, watching her. When Hanna turns around, the girl walks off.

In the same episode, we see Mona and Toby talking in A's lair. Mona refers to someone by saying: "They need to understand she's in charge". While this might imply that the Big A is a female.

In "Out of the Frying Pan, Into the Inferno", Big "A" is seen in the "A" liar using a blowtorch to burn a doll representing Hanna. The girl was seen wearing a red jacket and has red nail polish on. (Some fans question Big A's true gender, but it seems unlikely that Big A is a male)

In "Dead to Me", Big "A" was supervising an "A" team member digging up Ali's grave from "That Night". She was wearing her red coat, curly blond hair was seen, and you could see her face - somewhat. However, that blond hair could have been that wig seen in a previous episode in the "A" lair and she could have been wearing that Ali look-a-like mask. Emily would later state that she was in charge.

In "Hot Water", Big "A" was watching Spencer before turning around and leaving. Spencer would try to follow her, but Big "A" disappeared.

Identity
There is almost no information about Big "A" or what her motives are. All we know is that the Big "A" is female and has blonde hair. It can be speculated, however, that Big "A" could be impersonating Alison by wearing the blonde wig that was seen in "A's" Lair in previous episodes. It is also be important to note that Big "A's" red trench coat is often a symbol repersenting Alison DiLaurentis, therefore implying that Big "A" could, in fact, be Alison.

It has been widely speculated that Big "A" is Alison DiLaurentis, or a twin of some sort (see Courtney DiLaurentis, a book character). Some fans suspect Alison because Big "A" makes her appearence wearing a red trench coat, similar to the red trench coat of Vivian Darkbloom (the alter ego of Alison DiLaurentis, who used this persona to try to  find out who A is). Supporters of this theory think that Ali (or Courtney) had a twin who hated her, and started the A-Team to ruin the lives of her and the Liars. Some think that it is not likely that Alison is Big A because she was also stalked by A. It is possible for her to have a twin.

Another theory that recently started trending is that Aria Montgomery is the "Big A." Fans have pointed out the fact that Aria recieves almost little to no torment from "A", hasn't had many confrontations with A (until the season 3 Halloween episode), along with a wide range of other clues taken from the show. They also point out that Aria was the last one seen wearing Vivian Darkbloom's coat, before we see Big "A" wearing the same coat when visiting Mona in UnmAsked. They point out that Aria showed no hesitation, or awkwardness, when she was about to wear her dead best friend's coat for the "first time". In The Goodbye Look (season 2 episode 2), Mona says to Aria: "Hey, Big "A"!" There are some things that don't add up to this theory, however; Aria recieves texts when she's alone, and Aria was almost thrown off the Train in This Is A Dark Ride. Some fans ask why A would try to kill Big A.

Big A might wear a mask, so that no one knows who she is. Also, it could be a mask that looks like Alison's face  to throw people off.

Big A was seen by 3/4 of the Liars:
 * Emily - during "That Night" (flashback; in "Dead to Me").
 * Hanna - during her fake interview (in "Misery Loves Company").
 * Spencer - while she was walking (in "Hot Water").
 * Aria - ???