A common theme is friendship. Their unique bond, whether it's a platonic or a more romantic - leaning one, is often explored. It shows how they support each other through Gotham's chaos.
One great 'DC Comics Poison Ivy x Harley Quinn Fanfiction' is 'Green and Red'. It beautifully captures their complex relationship. The author does a wonderful job of showing Ivy's protectiveness over Harley and how their love defies the chaos around them.
Another could be a love triangle of sorts. In the fanfiction, Poison Ivy might be jealous of Harley Quinn's growing friendship with Batman. Harley is caught in the middle, torn between her loyalty to Ivy and her newfound respect for Batman. This creates a lot of tension and interesting character dynamics.
In some fanfictions, their relationship starts as pure enmity. Batman is constantly trying to stop Poison Ivy and Harley Quinn's criminal activities. But as the story progresses, they might find common ground. For example, they all might have a shared enemy that forces them to work together briefly.
One great Harley Quinn and Poison Ivy fanfiction is 'Green Love'. It beautifully portrays their relationship in a more innocent yet deep way. It focuses on their shared adventures and how they support each other through different challenges.
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.
Perhaps the story could focus on how Harley Quinn and Poison Ivy adjust to their new family dynamic. Harley might be the more impulsive and fun - loving parent while Poison Ivy is more protective and nurturing. The baby could also bring out a softer side in their villainous personas, leading them to consider a more peaceful existence.
I highly recommend 'Partners in Crime'. In this fanfic, Harley and Ivy team up to take on some new villains in Gotham. It's full of action and at the same time, shows their relationship evolving. Another one is 'Under the Stars'. It has a more romantic tone as they go on a camping trip together, away from the city lights, and discover new aspects of their relationship while enjoying the beauty of nature.