Yes, there are some out there. You can start by checking fanfic websites like Archive of Our Own. Just search for 'naruto x harley quinn' in their search bar and you might find some interesting stories that combine these two very different characters from different universes.
A plotline might involve a magical accident that merges the two universes. Naruto and Harley Quinn are forced to work together to separate the universes again. Along the way, Naruto could teach Harley Quinn about the value of friendship and loyalty, while Harley Quinn shows Naruto how to be more spontaneous. Or perhaps Harley Quinn is being hunted in the Naruto world by some ninja who mistake her for a dangerous threat, and Naruto has to protect her.
In Harley Quinn x Joker fanfic, the character development is often a focus. Harley's transformation from a psychiatrist to a criminal sidekick is interesting. Writers may play with different timelines and scenarios in the fanfic. For example, they might explore what would happen if Harley finally broke free from the Joker's influence earlier than in the original story. This can lead to various plot twists and new character arcs for both Harley and the Joker.
One interesting Naruto Harley Quinn fanfic could be one where Harley Quinn somehow gets transported to the Naruto universe. In this fic, she might interact with Naruto and his friends in a really comical way. Maybe she tries to use her wacky weapons and fighting style against the ninja, but quickly realizes she needs to adapt. It could be a fun read for those who like crossovers.
Writing a Naruto and Harley Quinn fanfic is no easy feat. You have to balance two very different universes. One way to do it is to focus on the themes that both characters share. For example, they both have a sense of loyalty, albeit in different ways. Naruto is loyal to his friends and village, and Harley Quinn has a certain loyalty to those she cares about in her own twisted way. Use this as a foundation for their relationship in the fanfic. Also, don't be afraid to create new villains or threats that would require their combined skills to defeat. This will make the story more engaging and show how well they can work together.
One great 'Deadpool x Harley Quinn fanfic' is 'The Unlikely Duo'. It has a really interesting plot where they team up to take on a common enemy in a very chaotic and humorous way.
A fanfic could explore a scenario where Harley Quinn, in her attempts to reform, crosses paths with Bruce Wayne. He initially distrusts her, but as they interact more, they start to understand each other on a deeper level. For example, Harley could be helping at a local shelter that Wayne also supports, and they gradually build a connection.
Well, 'Harley Quinn's New Companion' is a fanfic that stands out. In this story, the reader gets involved in Harley's adventures in a really immersive way. The author does a great job of showing Harley's complex emotions towards the reader. There's also 'Harley and the Reader: Unlikely Allies' which shows how the two characters, who seem so different at first, end up relying on each other.
I really like the fanfic 'Harley and the Red Hood'. In this story, Harley Quinn and Jason Todd are brought together by a common enemy in Gotham. The story is full of action and their interactions are really interesting. You can see how their different backgrounds and personalities clash and then start to mesh as they face various challenges together.
A Harley Quinn x Batman fanfic can be really interesting. It often explores the complex relationship between the two characters. Harley, with her wild and unpredictable nature, and Batman, the brooding and justice - seeking vigilante. Writers might create scenarios where Harley tries to break free from her toxic relationship with the Joker and finds an unexpected connection with Batman. It could involve Harley helping Batman in his fight against crime in Gotham, while also dealing with her own internal struggles.