Quinn's origin story features her as a former psychologist at Gotham City's Arkham Asylum who was manipulated by and fell in love with the Joker, her patient, eventually becoming his accomplice and lover.

Following her introduction to the comics in 1999, Harley Quinn was depicted as the former doctor turned sidekick and lover of the Joker as well as the criminal associate and best friend of Poison Ivy.

After years of scarce appearances in comics, Quinn returned in a leading role in 2009 with the Gotham City Sirens series, as part of an unstable alliance with Poison Ivy and Catwoman.

[5] In 2021, DC's line-wide Infinite Frontier relaunch brought Quinn back to Gotham City and reestablished her as a superhero seeking redemption for her past actions.

Harley Quinn's abilities include expert gymnastic skills, proficiency in weapons and hand-to-hand combat, complete unpredictability, immunity to toxins, and enhanced strength, agility, and durability.

[13] The character idea dated back in 1991, when Dini witnessed his college friend Arleen Sorkin play a jester in an episode of Days of Our Lives.

[37][38][39][40][41] The story received wide praise and won the Eisner and Harvey awards for Best Single Issue in the same year and was later adapted into an episode of the same name in The New Batman Adventures in 1999.

[20] Kesel's run on the series began being published in December 2000, and was about Harley Quinn leaving the Joker and becoming a solo criminal, alongside a supporting cast of henchmen named the Quinntets.

[48][12] After years of scarce appearances in comics, Harley Quinn resurfaced in a leading role in July 2009 with Gotham City Sirens, a team-up title created by Dini.

[50][51][52] The series also expanded on Harley Quinn's background and early life; in Gotham City Sirens #7, Dini established the character's hometown being Brooklyn, based on her accent and also introduced her dysfunctional family, with her swindling father being described as the main reason for her pursuing psychology.

As part of the New 52 reboot in September 2011, Harley Quinn was reintroduced by Adam Glass as a prominent member of the supervillain team Task Force X in the relaunched Suicide Squad series.

[22][57] The character was heavily redesigned to fit the tone of the book, and was inspired by Harley's designs in the video games Batman: Arkham Asylum and Batman: Arkham City;[58][59] her color motif was changed to red and blue, her jester costume was replaced with a revealing ensemble consisting of a corset and hot pants, her skin was bleached white, and her previously blonde hair was altered to half-blue and half-red.

[65] Harley Quinn's second ongoing series, written by husband and wife Jimmy Palmiotti and Amanda Conner, with the interior art illustrated by Chad Hardin and John Timms, explored Harley Quinn leaving Gotham City and starting her own life in her hometown of Brooklyn, depicting her as a landlord in Coney Island, where she shares an apartment building with a supporting cast of "sideshow freaks".

[66][12][67][68][69] Considered to be the most defining writers to work on the character since Dini and Timm, Palmiotti and Conner reinvented Harley Quinn as an antihero who has left her controlling relationship with the Joker behind.

Harley Quinn's DC Rebirth design included pink and blue dyed hair tips and a jacket inspired by Margot Robbie's portrayal of the character in the 2016 film Suicide Squad, a change established in the last issues of her New 52 series.

[84] Harley Quinn's relaunched ongoing series is a direct continuation of the former, with Conner and Palmiotti still writing for the character, and Hardin and Timms illustrating the interior art.

[93] In the second part of the story, Dini and Palmiotti explained Harley Quinn's change in costume, establishing the character's modern design as a reflection of her having left her relationship with the Joker.

[94][95] For the 2021 Infinite Frontier relaunch, Harley Quinn is moved back to Gotham City as a superheroine, where she frequently interacts with and aids the Batman family, and she is given a new design by Riley Rossmo.

[96] Harley Quinn's fourth ongoing series, written by Stephanie Phillips and illustrated by Rossmo, depicts her "actively looking to make up for her past sins", alongside a former Joker henchman named Kevin.

[100][101][20] Following her transition to the main DC canon in 1999, Harley Quinn was established as having immunity to toxins and enhanced strength, agility, durability, and reflexes, which she received after having been injected with a serum concocted by Poison Ivy.

Her intellect extends to her psychological, tactical and deception abilities, but she does not stand out for particular strategic or scientific skills and often remains subordinate to the Joker, who between the two is the genius and the inventor.

Harleen helped the Joker escape and, renaming herself Harley Quinn, became his sidekick in hopes that she could win his love, going on a crime spree across the United States of America.

Recovering in Arkham, Harley decides that the Joker will never truly love her, before returning to her devotion upon seeing that he has left her a rose in a vase by her bedside table, with a note hoping that she gets better soon.

Following the Quinntet's dissolution, Harley Quinn moves to Metropolis with her best friend Poison Ivy, where she works as a love columnist in the Daily Planet under the alias Holly Chance.

[4] Harley Quinn then spends a year applying for parole, only to see her request systematically rejected by Bruce Wayne, the layman member of Arkham's medical commission.

Harley Quinn then joins forces with Poison Ivy (Pamela Isley) and Catwoman (Selina Kyle) in the series Gotham City Sirens.

The dysfunctional, "horrible" experience while visiting family causes her to return home to the Sirens' shared Gotham City hideout where Harley, Catwoman, and Poison Ivy spend the rest of Christmas together.

However, Harley ultimately chooses instead to release the Joker from his cell, and together the two orchestrate a violent takeover of the facility that results in most of the guards and staff members either being killed or taken hostage by the inmates.

Harley Quinn moves back to Gotham City in an attempt to reestablish herself as a hero, aiding the Batman Family and trying to make up for her past "where she often enabled the Joker".

[187] Harley Quinn appears as an unlockable character in DC Universe Online, initially reprised by Arleen Sorkin before being replaced by Jen Brown starting in 2016.