Pretty Little Liars ran for seven seasons between ABC Family and Freeform. The series followed four high school girls a year after their best friend Alison disappeared. At the pilot's end, Hanna, Aria, Spencer, and Emily have all received a message from the mysterious, "A." Their stalker is excellent at their job, somehow knowing everything about them all the time. The mystery kept fans on the edge of their seats, wondering who "A" was as "A" terrorized the group. The show dominated social media, being the most tweeted about television series with all the show's fans trying to guess the identity of the infamous "A."
ARIA MONTGOMERY
One of Aria's biggest issues comes from not thinking with her head, but with her heart. It's well-known that becoming romantically involved with your teacher is not a great idea, even if it is a trope that appears in many teen dramas. The relationship would only cause problems for anyone involved, and Aria and Ezra's was no different. Aria was meant to be smart even if not to the extent Spencer was, and yet common sense managed to escape her when it came to romance. While Aria may have had her moments, her inability to grasp that a romantic relationship with her teacher was a bad idea was enough to have her so low. Aria even joins the A-team to avoid Ezra learning the truth about a statement she made about him.
HANNA MARIN
While Hanna may not have been the brightest academically, she held some street smarts and was knowledgeable in the fields she cared about. When she needed to help figure out clues, Hanna would help, even if her most useful contribution came from an offhand comment. She could often go overboard, though, yet it was always to help or save the people she loved. Hanna was willing to do anything to protect her mother. She had also gotten Mona to help her in a scheme that forced Hanna to admit guilt to a crime and sound convincing.
TOBY CAVANAUGH
Joining the Rosewood Police young may have been the right move for Toby, but it also creates problems for him as well. Rosewood's constantly corrupt police force discourages individual thinking and makes things difficult for Toby when he wants to protect his friends. Toby did not have the best home life with his step-sister, Jenna, but he dealt with the hand he was dealt in life and made it through to the other side. After years of believing that Toby would race out of Rosewood the second he could, his choice to stay in town was one of the biggest shocker he could provide. The other shocker was when Toby joined the A-Team for awhile.
EMILY FIELDS
Emily tended to be considered academically bright, but not to the extent Spencer was. Overall, Emily managed to land about average. She was not the smartest of the main characters, nor would she land last on the list. Instead, Emily was a reliable friend and contributor in determining who "A" was. Unfortunately, she had bad habits of who to trust and was often deceived. However, Emily does undergo major development from a timid girl to a dynamic woman. The development does not come lightly, as it brought about by stalking, murders, and other not-so-nice activities.
EZRA FITZ
Technically, Ezra would be closer to the top of the list had it not been for a few critical choices. As one of the main characters who had graduated college by the beginning of the series, Ezra would have more academic intelligence than many of the other characters. Just like Aria, however, he lacks common sense. While the series attempts to justify it later, suggesting that Ezra had been manipulating Aria to gain knowledge for a true crime book, it still comes off as creepy and uncomfortable, especially when they get back together. However, the type of spying he had done does require a certain level of intellect.
CALEB RIVERS
As a teenage hacking genius, Caleb was often able to help the girls by using his computer skills. Caleb was an essential part of the team to learn the identity of "A." However, he was no match for the brains behind the game. Creators thought he was interesting enough to gain the spin-off, Ravenswood, following Caleb after he discovers some disturbing news. But fans did not have the same reaction, and the show was canceled. Once the series ended, Caleb was brought back to Pretty Little Liars, where he explained what happened in Ravenswood, giving closure to Caleb's storyline.
ALISON DILAURENTIS
Being on the run for over a year is not easy, but Alison accomplishes it anyway. After being stalked by "A" and buried alive in her front yard, Alison figured it was better to run than stay in Rosewood. Her street smarts kept her alive until she returned home. Alison goes through a lot in her life. Due to the experience of being on her own, she understands that she had not been the nicest person to her peers. She may not be the brightest academically, but to accomplish what she had takes a real level of intelligence. Alison even brought her skills to the short-lived Pretty Little Liars: The Perfectionists.
CECE DRAKE (CHARLOTTE)
As the second "A" in the series, Cece successfully terrorizes the girls for four seasons until she reveals herself to Alison. Flashbacks showed Cece quickly reading through books and school work. Cece's stalking techniques take things up a notch, as well. In "Welcome to the Dollhouse," Cece steps up her game by kidnapping Aria, Hanna, Spencer, and Emily after setting them up to be arrested. When each of the girls wake up in their bedrooms, they slowly figure out the truth when they walk into the hallway and discover they are in an underground bunker.
SPENCER HASTINGS
Spencer is the most academically brilliant of the Liars, with excellent grades and an unmatched study streak. She has perceptive in ways other characters do not, and although it makes her a bit more paranoid, she has every right to be. While Spencer does have her moments such as joining the A-Team, her genius ways of determining guilty parties and deductions towards the identity of "A" make up for it. In the series finale, Spencer must utilize her genius when she is pit against "AD," her twin sister, Alex Drake.
MONA VANDEREWAL
Going from a known nerd to Hanna's best friend, to the first "A" reveal, Mona, invented what Pretty Little Liars: The Perfectionists would refer to as "a game." Keeping track of the Liars' whereabouts at all times was a full-time job, but throughout her time spent as "A," she never gave herself away. Other than a few moments where Mona may not have gotten rid of all the evidence, Mona was on par with Spencer in the ability to narrow down suspects in later seasons. Mona's growth from enemy to friend shows her intellect as she understands her wrongdoings and moves forward past them. Proving herself to be the smartest of them all, Mona had brought Alex and Mary Drake with her to Paris, keeping them in their own dollhouse.