Harley Quinn: The Wonder Years (1993-2001)
Prestige Format Edition. Origin of Harley Quinn outside of D.C. continuity. Paul Dini & Bruce Timm story. Bruce Timm cover & art.
The beginning:
The episode opens with the Joker and his new sidekick, Harley Quinn, attempting to kill Commissioner Gordon, but Batman thwarts their plan. Batman then returns to the Batcave to discuss Harley's past with his butler, Alfred Pennyworth.
Harley's origin:
Harley Quinn, formerly known as Harleen Quinzel, was a psychologist at Arkham Asylum who became the Joker's accomplice after meeting him. She took on the name Harley Quinn and became involved in an abusive, codependent relationship with him.
Harley's plan:
Harley wants to impress the Joker by killing Batman herself, but Joker eventually finds out and becomes angry and intimidated. Batman then taunts Joker, saying that Harley got closer to him than he ever did. The episode ends with Harley in the hospital after the adventure, but she's still interested in the Joker after he leaves her a rose.