Introduced in Pretty Little Liars as Hanna Marin's best friend, Mona initially harbors a grudge against the protagonists, using her intelligence and resources to torment them anonymously as "A".

Considered the most knowledgeable character in the series,[1] Mona is versed in computer hacking, foreign languages, singing, empathy, and manipulation.

Initially a supporting player, the TV character gained much popularity among viewers and critics, drawing recognition from Entertainment Weekly, CNN, MTV, and others, prompting producers to expand her role.

[3] During the TV series' run, producer I. Marlene King acknowledged Mona as a "beloved character.

"[4] By the end of the show's run, Dana Getz of Bustle.com declared that Mona had become "the most important character in the series.

A teenage resident of Rosewood, Pennsylvania, she has white-blonde hair, light blue eyes, and a few freckles.

As Mona's birthday is coming up, she chooses Naomi, Riley, Hanna and some other girls to be her "next-in-lines" so she goes to buy dresses with them.

Mona is introduced as an alluring and witty teenager, whose full intelligence is gradually revealed as the series progresses.

[6][10][11] Her high IQ is further established in the Season 3 episode "Mona-Mania", when she competes against rival Spencer Hastings in a high-school quiz game, and ultimately wins.

In the Season 2 finale, Alison's friends learn that Mona has used her talents to manipulate and torment them anonymously.

In the mid-season finale, Mona invites the Liars to her birthday party, but uninvites Hanna after "A" sends her a fake message.

When "A" begins sending threatening notes to Mona, she grows closer to the Liars and becomes a part of their group.

In "Unmasked", Mona is still helping the Liars, who haven't fully accepted her yet, and volunteers to drive Spencer out to the Lost Woods Resort where they find "A's" lair.

Parrish, who had learned of "A's" identity in the novels, revealed she was pleased that the situation had not been changed in the TV series.

[14] Mona joins forces with a girl known as Red Coat and begins recruiting people for the "A" Team, including Toby Cavanaugh and Lucas Gottesman, while still staying at Radley.

Mona is still allied with Liars until she begins helping Ezra Fitz with his book, because he blackmailed to expose her illegal "A" activities.

In the mid-season finale, she is supposedly killed by "A" after acquiring information that proves Alison is the alleged anonymous tormentor.

They are eventually let back in the dollhouse but Mona is taken away by "A" and taken to the hole, while the other girls experience their own personal torture.

Mona returns to Rosewood in "She's No Angel" and is nervous of what Alison will do to her after learning that she staged her death and framed her for it.

The Liars are investigating around Leslie's animal lab to see what she is hiding when suddenly the lights go out and Mona emerges.

She helps the Liars thwart Alex's plans and brings a police officer to arrest her and Mary.

Appearing in the penultimate segment, she is the last of the longtime characters to be seen in the series, surpassing even the Liars, prior to an epilogue.

[16][17] The show's breakout player, Mona Vanderwaal was named the greatest character in the TV series by PrettyLittleLiars.com, which cited her cleverness, multiple layers, and chemistry with Spencer Hastings and Hanna Marin.

[2] MTV named Mona one of the best characters on television in 2014, labeling her "smart, ferocious, and consistently interesting.

"[10][18] In a related review, Dana Getz declared that Mona "quietly became the most important character in the series.

"[10] Stephanie Goldberg of CNN was less positive, finding the revelation "obvious" while also citing a lack of change from the book series.

[13] Seventeen magazine's Michelle King noted that the episode sent "chills up our spine," and reviewed it favorably.

[21] At the conclusion of the TV series, an article from Hypable.com lauded Mona's impact on the show, calling her "Brilliant, hilarious, brave, and beautiful," also labeling the character "always fun to watch".

[24] Writers for numerous media outlets, including Entertainment Weekly, Hypable.com, BuddyTV, and Bustle.com, called for a spin-off focusing on Mona Vanderwaal.

[24][25][26][27] Jessica Goldstein of Vulture highlighted Mona's fashion choices while also praising her relationship with Mike Montgomery, saying, "I like her little Breakfast at Tiffany's look, her winged eyeliner, and even her overdone updo, because such devotion to hairspray seems very Mona-esque to me.