Red Coat's origin dates back to Alison as she used to wear the costume when she was being her alter-ego, Vivian Darkbloom. After her disappearance, Alison wore the red coat to move around and watch over the Liars.
The leader of the A-Team and Big "A", Red Coat was Charlotte's first disguise before she moved onto wearing the black hoodie. She used this to trick the Liars into thinking she was Alison, and also spied and stalked them using it.
Sara was Charlotte's helper and was used as a decoy Red Coat to distract the Liars on the night of the lodge fire.
Red Coat is the main antagonist of the third and fourth seasons of the television series Pretty Little Liars, as well as being the secondary antagonist of the sixth season. She is the leader of the "A-Team" who dons an Alison mask and a red trench coat. She is revealed to be Charlotte DiLaurentis and Sara Harvey. However, Red Coat originated from Alison DiLaurentis as she used it as a disguise to hide from and spy on "A".
Mona Vanderwaal is revealed to be "A" and is placed in Radley Sanitarium for mental treatment. After being placed in Radley, a nurse walks into her room and informs Mona that she has a visitor. In walks Red Coat, whom Mona tells she did everything she asked her to. Red Coat then takes over the game of "A" from Mona and begins texting the Liars. She is seen buying hoodies for what would come to be known as the A-Team and is later spotted various times by the Liars, who identify her as the blonde leader of the A-Team. The Liars hatch a plan to catch the blonde and throw a party at the Thornhill Lodge, with Spencer and Toby working on the inside as A-Team members. Red Coat flies in on a plane and goes through the woods, just as someone sets the Lodge on fire with Emily, Aria, Hanna and Mona still inside. After passing out from the smoke, Hanna is pulled out by Red Coat and sees her as Alison. She tells the other girls but only Spencer believes her, eventually starting to doubt it herself. Eventually the Liars discover that there are actually two Red Coats, one of them being "A" and is revealed to be CeCe Drake, while the other is an ally to the Liars and is revealed as Alison DiLaurentis, who is using the disguise to hide from "A". After being caught, both girls seem to stop wearing the disguise, with CeCe now wearing a black hoodie and Alison getting a new disguise. The Liars forget about Red Coat; however, it is eventually revealed that there is a third Red Coat, this one having acted as a decoy and is "A's" ally. CeCe reveals herself as Alison's sister, Charlotte DiLaurentis and tells the story of how and why she became "A", while the third Red Coat sets up a bomb inside Radley for her. CeCe reveals that it was her who visited Mona in Radley, but in a red robe and reveals that she became "A" because the Liars were happy that Alison was gone after disappearing. CeCe then reveals that it was the decoy Red Coat who got off the plane. In a flashback, Red Coat gets off the plane and makes her way through the woods, where she meets with CeCe. She reveals herself as Sara Harvey. The Liars are shocked by this and believe CeCe may be lying. CeCe also reveals that it was Sara who went to Wilden's funeral dressed in a black veil. The Liars get into Radley and come upon Sara in the hallway, who orders them to leave immediately. The Liars manage to subdue her and stop the bomb, and CeCe runs up to the rooftop of Radley. Alison asks the girls to help her stop CeCe from jumping and Sara attempts to run off, only to be grabbed by the hood of her coat by Emily. She says she "tried to keep Emily safe" and Emily punches her. Sara tries to get up back up but accidentally places her hand on an electrical box, causing her to be electrocuted and severely damaging her hands. The Liars are horrified but do not attempt to help her. They make their way to the roof where they try to calm down CeCe, but its Alison calling her Charlotte that makes her decide not to jump. CeCe jumps back down and declares "game over".
- Alison DiLaurentis wore the disguise in order to sneak around Rosewood, but was not involved with the "A" game as far as we know.
- Charlotte was the Red Coat who bought the black hoodies, burned the Hanna bobble head, watched Mona dig up the grave and assisted her, donned the Emily mask, snuck under the DiLaurentis home, went to the Hoe Down and locked Emily inside the sawmill.
- Sara was a decoy Red Coat and was used to distract the Liars. She rescued the girls at the lodge fire, sat beside Charlotte in their lair and also tried to set off a bomb at Radley. Sara also was the Black Widow.
- Technically Red Coat is the main antagonist of season 5 and 6 as well, however by this time Charlotte had moved onto another disguise and Red Coat's identity belonged only to Sara.
- Red Coat is unique, in that she's a protagonist, big bad, and henchmen. Alison being a protagonist, Charlotte being the big bad and Sara acted as a henchmen.