Harley Quinn & Poison Ivy

Harley Quinn and Poison Ivy in their uniform wear from Arkham Asylum.

Harley 

Poison Ivy

In their cell at Arkham Asylum and the famous "kiss".

Poison Ivy, Batman and Harley Quinn.

Harley Quinn was first created for the Batman Animated Series in 1992 by Paul Dini and Bruce Timm. The episode became so popular that DC invested in the character and began to develop an intricate back story. Born Harlene Quinzel, she actually met the Joker while she was an intern at Arkham Asylum. After interviewing him once, she instantly fell in love and helped facilitate the first of many escapes. Later on Joker is brought back to Arkham beaten and dying, and Harley Quinn is born as she felt she could help the Joker with his many crime sprees. Joker and Harley’s relationship is rocky at best as she is constantly leaving and returning to him. In one story line the Joker kicks her out of his gang and Harley befriends Poison Ivy. For a short stint Harley and Poison Ivy were the Gotham Queens of Crime. Poison Ivy gives Harley a serum that makes her immune to many toxins and gives her strength – other than this instance, Harley has never had powers. Harley eventually returns to the Joker to find his feelings for her have become genuine. Scared at the thought of real human emotion, the Joker’s only logical response is to kill Harley. Harley survives the Joker’s attempted murder and returns with Batman. After shooting Joker in the shoulder, Harley leaves the relationship. She has been in and out of Arkham countless times as both a patient and a doctor throughout her life. Harley then joins the team Birds of Prey led by Oracle (a paralyzed Batgirl) only to leave shortly after. Currently Harley is featured in the comic Gotham City Sirens along with Poison Ivy and Catwoman.

Poison Ivy is a brilliant botanical biochemist. Pamela Isley is a fervent eco-terrorist out to save the world's plant life by any means necessary. She often finds herself at odds with Batman, though they have, on occasion, fought on the same side. She has had a long friendship with Harley Quinn and is responsible for Harley's meta-human abilities. Ivy, Harley, and Catwoman later teamed up as the Gotham City Sirens. Post-New 52, she was a member of the Birds of Prey for a time before betraying them to further her cause.