You can try Archive of Our Own (AO3). It has a large collection of fanfiction, including ones about Joker and Harley Quinn. Just use the search bar and type in their names, and you'll likely find some relevant lemon fanfics, but make sure to check the ratings and tags.
Well, 'Tainted Love' is quite interesting. It presents a scenario where the Joker and Harley Quinn's relationship is tested in new and unexpected ways. The story has a lot of character development and shows how their love, if you can call it that, is both destructive and yet strangely endearing.
I really like the fanfiction 'The Dark Romance of Joker and Harley'. It has a great take on their relationship, showing how they both feed off each other's madness. 'Harley Quinn's Revenge' is also good. Here, Harley decides to take revenge on the Joker for all the wrongs he has done to her. It's an exciting read as it shows a different side of Harley. Then there's 'Joker's Secret Plan' which involves a lot of mind - games between the two characters, making it a very engaging fanfiction.
One great 'Harley Quinn Joker Fanfiction' is 'Mad Love Reimagined'. It delves deeper into the complex relationship between Harley and Joker, exploring Harley's psyche as she falls deeper into the Joker's chaotic world. The writing style is vivid and really brings out the twisted nature of their relationship.
Well, Harley Quinn first met the Joker when she was working in Arkham. The Joker is this super - insane and manipulative guy. He saw an opportunity in Harleen. He started to play mind games with her. Told her all these crazy stories and ideas. Harleen, being young and a bit naive in a way, fell for it. And she started to see the world through his eyes. Before long, she was breaking him out of Arkham and joining him in his criminal sprees. Their relationship is complex. It's not just love. It's more like an obsession on Harley's part and a tool - like use by the Joker.
No, Harley Quinn has distanced herself from the Joker. The comics have shown her evolving and growing as a character separate from that toxic relationship.
Harley's character could develop in many ways. She might become more protective and motherly, which is a big change from her usually wild and carefree self. This new - found sense of responsibility could make her question her relationship with Joker and the life of crime they lead.
One possible scenario in this fanfiction could be Joker and Harley Quinn finding themselves in the world of Twilight. Maybe they would disrupt the vampire - human dynamics there. Joker might see the vampires as new playthings, while Harley could be intrigued by the idea of a different kind of 'love' like the one between Bella and Edward. But they would also bring their own brand of chaos.
They're popular because their relationship is so complex and intense. The Joker is this chaotic, unpredictable character and Harley is completely devoted to him, despite his abuse. It makes for a really interesting dynamic to explore in fanfiction.