Described in the comics as a "psychoanalyst turned psycho," Harleen Quinzel was once a brilliant psychologist. However, she fell in love with her most disturbed patient, The Joker, and soon after took on the persona of "Harley Quinn."
In the comics, Harley is among the most feared of the Squad members because she's both unpredictable and uncontrollable. She's a surprisingly strong martial artist and Deadshot develops something of a soft spot for her. This is the on-screen debut for the character and we'll get to see both her life as Dr. Harleen Quinzel, attempting to treat the Joker, and as Harley Quinn, the giggling supervillain and Squad member.