Info Harley Quinn:
Created by Paul Dini and Bruce Timm.

As suggested by her name (a play on the word "harlequin"), she is clad in the manner of a traditional harlequin jester. She is one of the rare characters to have originated in an animated series and thereafter been added to the comic book continuity, as opposed to the other way around. She is also the only such character to have gone on to have an ongoing eponymous comic book.

Harley is an Arkham Asylum psychiatrist who falls in love with the Joker and becomes his accomplice and on-again, off-again girlfriend. She becomes fascinated with the Joker while interning at Arkham, and volunteers to analyze him. She falls in love nearly instantly with the Joker during their sessions. After helping him escape from the asylum more than once, she is caught by her superiors, who revoke her license and put her in her own cell. During an earthquake in Gotham City, she flees and becomes Harley Quinn, the Joker's partner-in-crime.

Source: wikipedia.org