In a fanfiction, they could be friends in an alternate universe where Harleen never met the Joker. They could work together to solve crimes in Gotham, with Harleen using her psychological knowledge to assist Batman in understanding the motives of the criminals. This would be a very different dynamic from the comics where their relationship is often adversarial because of her association with the Joker.
Another way to portray their relationship differently is to make it a romantic one. But not in the typical sense. It could start as a begrudging respect for each other. Harleen is drawn to Batman's sense of justice and Batman is intrigued by Harleen's complex mind. As they work together on a particularly difficult case, they start to develop feelings for each other, which is a far cry from their relationship in the original comics.
Their relationship could be portrayed as a more mentor - mentee relationship. Batman could see the potential in Harleen to be redeemed and takes her under his wing, teaching her how to use her skills for good instead of for the Joker.
One plot idea could be Harleen Quinzel trying to reform herself and seeking Batman's help in leaving her past as Harley Quinn behind. She might offer him information about the Joker's next move in exchange for protection and a chance at a new life.
They often showcase her complex personality and her relationship with the Joker. The art style is usually bold and colorful to enhance the mood.
Dr. Harleen Quinzel in comics is often depicted as intelligent and manipulative. She has a complex relationship with the Joker and undergoes significant character development.
It has a unique blend of humor and drama. The character development of Harleen is really captivating.
Harleen Quinzel was a psychiatrist at Arkham Asylum. She became obsessed with the Joker during her attempts to treat him. His chaotic nature and charm gradually drew her in, leading her to fall in love with him. This ultimately led to her transformation into Harley Quinn, abandoning her former life and morals to be with the Joker.
The key element is her job at Arkham Asylum. It put her in the path of the Joker.
Their relationship could be portrayed as a mentor - mentee relationship. Catwoman, with her years of experience, could be teaching Batman Beyond some of the more subtle aspects of crime - fighting, like how to read a criminal's motives just by observing their body language. Another way is to show them as rivals in a different sense. Instead of just fighting over loot, they could be competing to solve a mystery first. Or, they could be portrayed as reluctant allies. They don't trust each other completely, but they know that they need to work together to stop a greater evil.
It could be shown as a very strained relationship. For example, Wonder Woman might initially be very hostile towards Batman, seeing him as a threat to the order Superman has created. But as time goes on, she starts to see the value in his approach. There could be many tense confrontations between them that gradually turn into more respectful exchanges as they understand each other better.
In some fanfictions, the Naruto - Sakura relationship is portrayed as a slow - burn romance. Naruto's continuous efforts to protect Sakura gradually make her fall for him. In contrast, in the original series, Sakura was mainly focused on Sasuke. Fanfiction gives an opportunity to change that narrative.
Their relationship could be portrayed as a mentor - mentee relationship in a different way. Instead of Orochimaru trying to use Naruto for his own gain, he could genuinely see Naruto's potential and guide him in the ways of some of the more esoteric jutsu. For example, Orochimaru could teach Naruto about the secrets of the snake contract without any ulterior motives. Another way is to show them as reluctant allies. Maybe there's a common enemy that is so powerful that they have no choice but to work together, and over time, they start to respect each other's abilities.