Red Coat

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

- Mona to Big A

Big "A" 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.

We have only seen Big "A"  assumably four times. The first time is at the end of the season two finale, UnmAsked, where she visits Mona after being revealed as an A-Team member. Big "A" is seen wearing a red trench coat. Mona looks up to Big  A, and says: "I did everything you've asked me to." From this point, it becomes clear that she is the leader of the A-Team. The second time is at the end of the Season 3 episode of "Blood Is The New Black", where she is seen buying black hoodies and gloves for her workers. Again, she is seen wearing a red hoodie. The store owner says to Big "A": "So, are you buying this for a team?". There was also possibly a third sighting in 'Misery Loves Company', as Hanna looks into a shop window and see a girl with blonde hair and wearing a red trench coat on the other side of the road, watching her. She turns around, but the figure has gone. However, it is possible that this was just another sighting of Alison, like when she visits Spencer, Aria, Emily and Hanna in 'dreams'. The most recent we have seen Big "A" is in "Out Of The Frying Pan, Into The Inferno" when Big "A" is burning a bobblehead ( Representing Hanna) on fire with a blowtorch.

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 its 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 blowtoarch 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)

Identity
There is almost no information about Big "A" or what their motives are. Fans have almost no clues considering the fact that Big "A" never physically confronted the Liars. However, many fans have made certain theories:

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 her, because Big "A" makes their 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 supposedly 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.

Another theory that recently started trending is that Aria Montgomery is in fact the one behind all of this. Fans have pointed out to the fact that Aria recieves almost little to no torment from "A", never had any confrontation with A (until the season 3 Halloween episode), along with a wide range of 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 also 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". Another important clue is that in The Goodbye Look (season 2 episode 2), Mona says to Aria: "Hey, Big "A"!"

The A-Team
A is not a single person, but a team of multiple "A"s: the A-Team. It is unknown how many A's there are, possibly ranging anywhere from 3 to 20 members. Big "A" is most likely the one who created A and the A-Team, and she controls and gives orders to the A-Team members, or minor "A"s. Ultimately, Big A is the main A, since she (as we found out from Mona) is the mastermind behind this. So far, we only know two of the identities of "A": Mona Vanderwaal and Toby Cavanugh. Both of these characters are only A-Team members working for the Big "A".

It seems as if only certain A-Team members are active as "A" for a certain time period while the other members don't do very much. For example, if one were to assume that Toby has been "A" since the beginning of the show, then one would question how involved Toby was with A until he became more active since season 3, as Marlene King tweeted that Mona was the one who did mostly everything to the liars as A. Based on this, it seems as if Big A usually has a main worker to give orders to; at times switching in case of certain circumstances (Mona being sent to Radley, Toby's revelation as A in Misery Loves Company.

The Red Coat and Red Hoodie theory
Some fans have noticed that the person visiting Mona in unmAsked is wearing a red coat while the person shown at the end of Blood is the New Black is wearing a red hoodie. This leads certain fans to believe that the red coat and the red hoodie are two different people. One theory that recently started trending is that Ali has a twin, and both twins are alive while someone else died in their place. Ali could be the one with the red coat who tries to help the liars while Courtney is Big A and wears the hoodie. In this case, Mona would be considered to be a double agent  for the A-Team since she was saying to the red coat that she did everything she was told to, not the red hoodie. However, in the "Out of the frying pan, into inferno", we see a red coat girl, burning the doll of Hanna's face, which suggests that the theory can be wrong.