In most other media, the two are always at each other's throats. However, the Joker is no longer a villain in Harley Quinn.

Thanks to this history, Harley Quinn has given fans some of the biggest and most memorable fights. She's defeated villains ...

Those theories were soon confirmed, as Lady Gaga was reported to be playing Harley Quinn, the Joker's love interest. In the comics, Harleen Quinzel is a psychiatrist the Joker falls in love with ...