Real Name: Harleen Quinzel
Occupation: Criminal
Marital Status: Single
Base of Operations: Gotham City
Height: 5ft 7in
Weight: 115 lbs
Eyes: Blue
Hair: Blonde
First Appearance: Batman: Harley Quinn #1 (October 1999)
Created By: Paul Dini

While interning at Arkham, Harleen Quinzel became fascinated with one particular inmate, the Joker, and ambitiously volunteered to analyze him. She fell in love nearly instantly with the Joker during their sessions. After helping him escape from the asylum more than once, she was caught by her superiors, her license was revoked, and she was put in her own cell. During an earthquake in Gotham City, she fled and became Harley Quinn, The Joker's partner-in-crime.

In time, The Joker finds himself beginning to care for her. Naturally, this can't be countenanced, so he decides to kill her. After he takes her into his bed for what may or may not be the consummation of their relationship (Harley is apparently drugged), he lures her into a rocket ship, telling her, in part: "I've noticed some changes coming over me since you came into my life. I've been reminded what it was like to be part of a couple. To care for someone who cares for me. It's the first time in recent memory I've had those feelings... And I hate having those feelings!" He launches the rocket, soberly telling an enraged Harley that he will truly mourn her, before erupting into a fit of his trademark diabolical laughter.

The rocket lands in Robinson Park, where Harley first meets Poison Ivy. Ivy saves her, but after taking her in, recognizes Harley as Dr. Quinzel from the Arkham staff. When Harley regains consciousness, Ivy initially plans to kill her. The prospect of her own death totally fails to move Harley, and Ivy is curious as to why. She convinces Harley to tell her story, and comes to feel a kinship with Harley. Considering her another castoff, Ivy offers to help Harley take her revenge on both Batman and the Joker.

Ivy gives Quinn a treatment that immunizes her to various assorted toxins and Ivy's own poisonous touch. It also dramatically enhances Harley's strength and speed. Ivy intends this to give her new friend an edge on Batman and the Joker. Hot-blooded Harley, however, is angrier at the Joker than at Batman, and even initially works with the Dark Knight to help bring down the Clown Prince of Crime. While Batman eliminates the villain's muscle, Quinn chases the Joker up a damaged building, intending to send him falling to his death. Before she can do so, however, the Joker apologizes. Falling in love with him again, she forgives him on the spot, and serves as his lieutenant throughout the rest of No Man's Land.

One Year Later, Harley Quinn is an inmate at Arkham Asylum. Though she is planning a come back. confused with Harlequin, a distinct Teen Titans character originally appearing in the seventies.