As the name of the series suggests, the characters in Pretty Little Liars lie a lot to cover up some of the deepest, darkest parts of their lives. Spencer, Aria, Emily, and Hannah's secrets are far from the trivial, high school indiscretions of their classmates. Instead, the main characters hide homicides, assaults, thefts and so much more.
However, it is not only the main characters who hide things in the show; it seems that everyone in Rosewood has skeletons in their closet. With A determined to manipulate and create chaos in their lives, the liars find themselves puppets in the villain's twisted game — and willing to do anything to keep their secrets from coming out.
The Jenna Thing
After Alison lies and says she was Toby spying on the girls while they were getting dressed, she throws a firecracker (which she told her friends was a stink bomb) into his garage as an act of revenge. The garage catches fire and blinds Jenna.
This assault is one of the show's biggest secrets and leads to Jenna becoming one of the most beloved Pretty Little Liars villains. However, it is actually the liars, rather than Alison, who pay for this crime as they are constantly in fear that this secret will one day be exposed.
A and AD Blackmailing The Main Characters
When A (and subsequently AD) first starts blackmailing the girls, she already knows so many of their secrets. The liars are too scared to come forward and report this blackmailing to the cops as they know A would seek revenge. The blackmailing itself is one of the biggest secrets in the show.
It eventually transpires that it is not only the main characters who are at the mercy of A but also many others, including Jenna and Mona. Everyone ends up hiding the blackmail in order to prevent their secrets from getting exposed.
Aria Having A Relationship With Her Teacher
After meeting in a bar and immediately hitting it off, Aria is shocked to discover that Ezra is actually Mr. Fitz, her new English teacher. Ezra is equally as surprised as Aria led him to believe that she was in college — one of the biggest lies told on Pretty Little Liars. Despite this, and other obstacles, the two follow their feelings and engage in a relationship with one another.
As the relationship is inappropriate (not to mention illegal), Aria and Ezra muddle through trying to hide it from the school and her parents. Although the two eventually marry, fans had very mixed emotions about their relationship because Ezra abused his position of authority and the "happy ending" to this relationship undermines its problematic nature.
Ashley's Embezzling Money At Work
As a single mother, Ashley finds herself struggling to make ends meet. In an act of desperation, she steals money from an elderly woman's safety deposit box at work.
Despite the money subsequently being stolen and a fraudulent man turning up to claim the money, the truth never comes out. This secret did have fans biting their nails at times because, although they acknowledge Ashley should not have stolen the money, they recognize her honorable intention of trying to provide for her daughter.
Ezra Writing A Novel About Alison's Disappearance
Upon finding Alison's diary, it transpires that Ezra had a very brief relationship with Alison prior to her disappearance. But an even bigger secret is revealed: Ezra has been tracking Alison and her friends in hopes of writing a true crime novel about Alison's disappearance and revealing A's identity.
This was a shock to fans (as well as to Aria) because Ezra had so successfully hidden his true motivations for such a long time. Fans enjoyed this unforgettable Pretty Little Liars plot twist, as it was such an unexpected turn of events.
Aria Killing Shana
Having fallen head over heels in love with Jenna and wanting to kill Alison as revenge for what she did to her, Shana finds Alison and the girls in a theatre and makes her third murder attempt. In order to stop Shana and mistakenly believing that Shana is A, Aria hits Shana over the head with a gun and kills her.
One of the best-kept secrets on the show, the cops never find out that Aria is the culprit. This was not explained clearly and this storyline seemed to simply fade out. It seems reasonable to assume that there would have been a thorough investigation into Shana's death — and the discovery girls' fingerprints at the crime scene.
Charlotte's Entire Existence
As Charlotte was institutionalized at such a young age after nearly drowning baby Alison in the bath, her very existence is one of the best-kept secrets in Pretty Little Liars.
Alison's parents concealed this for many years and this is hidden from everyone, including the audience. This secret is the one that the whole series is based around and, when it comes out, it is one of the most exciting moments in Pretty Little Liars.
Melissa Killing Bethany Young
After sneaking out of Radley in Charlotte's clothes, Bethany is mistaken for Alison by Mona, who hits her over the head with a shovel. Melissa, also mistaking Bethany for Alison, buries an unconscious Bethany in an attempt to protect Spencer (who she thinks murdered her). As Bethany was not dead at the time of burial, it is actually Melissa who is responsible for Bethany's death.
Fans did not see this Pretty Little Liars plot twist coming at all. It was one of the rare moments on the show when a secret was about a (fairly) innocent accident. Though Melissa is by no means a fan-favorite character, fans sympathized with her, as she was devastated to know that she had buried a stranger alive.
Hannah Killing Archer Dunhill
While endeavoring to avenge Charlotte's death and steal Alison's money, Archer tortures Alison and is chasing her when Hannah accidentally hits him with a car, killing him instantly. Fearing that the cops would not believe it was an accident, the girls bury Archer's body and manipulate the situation to make it look like he has fled Rosewood.
Despite AD sending his severed finger to the police and Aria nearly getting caught with Archer's body in the trunk of her car, this secret never comes out because Mary Drake falsely confesses to the murder. Although an unfortunate end for Archer, fans were pleased that the girls do not go to jail and that Archer is no longer able to torture Alison.
Spencer's Real Mother Is Mary Drake
After spending her life believing her mother is Veronica Hastings, Spencer is devastated to discover that her birth mother is actually Mary Drake. Mary reveals to Spencer that she and Spencer's father had a one-night stand in which he believed Mary was her identical twin sister, Jessica DiLaurentis.
This secret is a particularly compelling one as it was kept from one of the main characters (rather than by one of the main characters, as usual). It means that Alison is Spencer's cousin (validating the long-running theme that the two had a familial relationship) and that Charlotte is Spencer's half-sister. This ultimately paves the way for Alex Drake, Spencer's evil identical twin, to be revealed as AD.