Dr. Harleen Quinzel was a psychotherapist at Arkham, until she was assigned to the Joker's case. She fell for him and joined him as his sidekick, taking on the persona of Harley Quinn. Just as crazy as her beau but with some lingering morality to get in the way, Harley is as prone to heroics as she is to villainy, and has all but separated from him. She's recently joined the Bat Family, cementing the 'hero' designation. She's often romantic with Poison Ivy, and close friends with Catwoman.