One idea could be that Harley Quinn and Power Girl have to team up to stop a common enemy. Maybe a powerful villain is causing chaos in the city and their combined skills are needed. Harley's unpredictability and Power Girl's super strength could make for an exciting dynamic.
One idea could be that they both get kidnapped by a mad scientist who wants to study their unique mental states. They then have to team up to escape the scientist's lair.
Well, a great plot could involve Harley Quinn's chaotic nature clashing with Bane's more methodical and brute - force approach. For instance, they are forced to work together on a heist. Harley wants to do things her wild way while Bane is trying to stick to a plan. As they argue and work through their differences, they start to respect each other. Also, perhaps they find out that they both have a vendetta against the same corrupt Gotham official, which brings them closer.
One idea could be that Harley Quinn tries to reform herself to be worthy of Batman's trust. Maybe she starts secretly helping Batman take down other villains in Gotham. Another could be a situation where they are forced to team up against a common, extremely powerful enemy, like a new supervillain who has a plan to destroy Gotham. And a third idea is that Harley Quinn has a change of heart about the Joker after seeing how Batman is constantly fighting for good, and she begins to see Batman in a new light, leading to a complex relationship between them.
One idea could be that the OC is a new villain in Gotham and Harley Quinn takes an immediate liking to their chaotic style. They team up to pull off a heist on one of Gotham's richest, with Harley's unpredictable nature and the OC's unique skills making for an exciting adventure.
One idea could be that Harley Quinn and Deadpool team up to take on a common enemy in Gotham City. Maybe a new super - villain who has a plan to take over both the criminal underworld and the hero world. They could have a really chaotic and funny dynamic, with Harley's zany antics and Deadpool's fourth - wall - breaking humor.
A possible plot for a Poison Ivy and Harley Quinn fanfic could be that they are framed for a crime they didn't commit. They then have to go on the run from the law and Batman. As they are running, they discover a secret underground garden that has plants with magical properties. Ivy wants to study these plants, but they also have to be careful not to be caught. Meanwhile, Harley is constantly cracking jokes and getting them into even more trouble, but also helping them out in unexpected ways.
There could be a plot where Poison Ivy discovers a new type of plant that has the power to make people tell the truth. Harley gets curious and tries it on some of the bad guys in Gotham. Meanwhile, Ivy is worried that this new plant could attract unwanted attention from the government or other powerful forces. They have to decide whether to keep it a secret or use it for their own purposes.
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.
One idea could be exploring their relationship before Harley fully embraced her criminal side. Maybe show how the Joker manipulated her in the early days. Another could be a story where they have to face a common enemy in the Suicide Squad universe that forces them to re - evaluate their relationship. Or perhaps a story where Harley starts to break free from the Joker's control and how he reacts to that.
One plot idea could be that Spiderman and Harley Quinn team up to take on a common enemy in Gotham. Maybe a new villain emerges who has technology that can disrupt both of their cities, so they have to combine their skills. Another could be a story where Harley Quinn, being a bit of a wild card, accidentally gets transported to Spiderman's New York and they have to figure out how to get her back while also dealing with the chaos she causes.