Who is Harley Quinn?

Harleen Quinzel was a highly intelligent, reckless psychiatric doctor. One of the inmates at her clinic was the Joker. She was fascinated by him and fell in love with him. She helped him escape several times before finally getting fired. However, Joker saw her as a threat and tried to kill her but to no avail. She was recovered by Poisen Ivy. She administered a serum that gave her supernatural powers. The two became a team and wanted revenge. They plotted against the Joker and Batman.