Not that Margot Robbie’s Harley Quinn needs a post-Joker romantic partner, but, hypothetically speaking, if she were to have one, it better be Poison Ivy. The pair go way back to one of the best episodes of Batman: The Animated Series, “Harley and Ivy,” where they team up and cause mayhem around Gotham. It’s great. And if Robbie gets her way, Harley and Ivy will be chaotic together in the DC Extended Universe as well.