Mona Vanderwaal is a fictional character in the Pretty Little Liars book series, its television adaptation, and the spin-off TV series Pretty Little Liars: The Perfectionists. In the TV shows, she is portrayed by Janel Parrish.
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". In the third season of the TV series, Mona gains a partner who eventually takes control from her. Afterward, she forms an unstable alliance with the protagonists, becoming a victim of her own creation. Considered the most knowledgeable character in the series, Mona is versed in computer hacking, foreign languages, singing, empathy, and manipulation. Though introduced as a villainess, she eventually takes steps toward redemption. Mona is the first 'A' in the show and the book.
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. In March 2015, PrettyLittleLiars.com named Mona the greatest Pretty Little Liars character. MTV also named her one of the best characters on television in 2014. During the TV series' run, producer I. Marlene King acknowledged Mona as a "beloved character." 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."
Novel series
Mona Vanderwaal was introduced in the first four Pretty Little Liars novels. A teenage resident of Rosewood, Pennsylvania, she has white-blonde hair, light blue eyes, and a few freckles. She is a formerly unpopular girl who was teased by Alison DiLaurentis and her friends, longing to be in their group. After Alison went missing, Mona befriended Alison's friend Hanna Marin, and they reinvented themselves as the 'it' girls of Rosewood Day.
Pretty Little Liars
Mona is introduced as Hanna Marin's best friend. She was initially considered nerdy, but together with Hanna she transformed into a beautiful 'it' girl during the summer three years prior. She is invited to Noel Kahn's beginning of the semester party, where she kisses his older brother, Eric. Whenever the school's mean girls, Naomi and Riley, say something mean about Hanna, Mona is there for her. Mona and Hanna get into numerous fights and arguments about Hanna's old friends, Emily, Aria and Spencer, because Mona thinks that she has been spending more time with them than with her.
Flawless and Perfect
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. She chooses champagne-colored dresses, but gets in a fight with Hanna, whom she accuses of sabotaging her birthday party. Later on, Hanna gets a package with the champagne-colored dress, and thinks it was Mona who sent it.
Happily, she puts it on and goes to Mona's party, even though the dress is too small. As she comes to the party, Naomi and Riley (who are in emerald dresses) give her weird looks, and when Mona comes out wearing the champagne-colored dress, Hanna realizes that "A" was the one who sent her the dress. Crying, she falls down and her dress rips, following the laughter of the party attendants, including Mona. Hanna tells Mona that she knows she got a liposuction because "A" sent her a message with the content, but Mona says that she should not believe everything she hears and calls her a liar. Later, Hanna gets a message from "A", but sees that it is not the usual blocked number. Even though she got a new phone and did not put in the phone-book yet, she recognizes the number and rushes to tell the girls, but gets hit by a car before she can do anything.