A plot could be that Harley Quinn's pregnancy is the result of some sort of experiment gone wrong in Gotham. Batman is investigating the case and realizes Harley is pregnant. He has to figure out how to stop whatever is causing the strange pregnancy while also protecting Harley from those who want to use her and the baby for their own evil purposes. As the story progresses, Harley might start to see Batman in a new light and consider changing her ways for the sake of her unborn child.
One possible plot could be that Harley Quinn discovers she's pregnant and tries to hide it from the Joker, fearing his reaction. Meanwhile, Batman somehow gets wind of it and feels a sense of responsibility to protect her, not just for the baby's sake but also because he realizes Harley is in a very vulnerable state.
Well, the plot could involve Harley Quinn and the Joker having an unexpected pregnancy. It could show how their relationship changes. The Joker might initially be dismissive or even angry, thinking it'll disrupt his plans. But Harley could be determined to have the baby and try to make the Joker understand the importance of family, or at least her version of it. There could also be a lot of drama with other villains or heroes reacting to the news of Harley being pregnant.
A plot could involve Robin being kidnapped by one of Harley Quinn's old associates who has a vendetta against her. Batman and Harley Quinn then have to work together to rescue Robin. During the rescue mission, Harley Quinn starts to see Batman in a new light and realizes that his way of fighting crime might be more noble than she initially thought. Meanwhile, Robin, while being held captive, manages to outwit some of the captors, setting up an exciting climax when Batman and Harley arrive.
Imagine a fanfiction where a new super - weapon is being developed in Gotham. Poison Ivy and Harley Quinn get wind of it and decide to steal it, thinking it could be used to further their own goals. Batman, of course, is trying to stop them. But as the story unfolds, they all realize that the weapon is far more dangerous than they initially thought. So, instead of fighting each other, they have to work together to destroy the weapon before it destroys Gotham. This forces them to put aside their differences and form an unlikely alliance.
A possible plot could be that Harley Quinn's sister is an undercover agent sent to infiltrate the criminal underworld of Gotham. She ends up getting involved with Harley and the Joker. As she gets closer to her sister, she realizes that Harley is more than just a crazy villain. She then tries to find a way to get Harley out of the criminal life while also dealing with Batman's suspicions of her true motives.
There might be some out there. You could start by looking on fanfic platforms like Archive of Our Own. Sometimes they have unique takes on the relationship between Batman and Harley Quinn, and a pregnancy storyline could add an interesting twist to their dynamic.
In many fanfics, Harley Quinn realizing Bruce is Batman can lead to some really interesting plot developments. Maybe she discovers it by accident, like seeing Bruce act in a way that's too similar to Batman's mannerisms. It could also be that she pieces it together from some clues that others have overlooked. This realization might make her re - evaluate her relationship with both Bruce and Batman, and it could create a whole new dynamic in the story.
One possible aspect of a Batman and Harley Quinn fanfic could be exploring their relationship in a different light. Maybe in a world where Harley Quinn is trying to break free from her villainous past and Batman is reluctantly helping her. It could be an interesting dynamic as they both have complex personalities.
A Batman and Harley Quinn fanfic could show them forming an alliance against a greater threat. For instance, a new super - villain emerges who is more dangerous than the Joker. Batman realizes he needs Harley's knowledge of the criminal underworld to stop this new foe.
One great 'Batman Harley Quinn' fanfic is 'Harley's Redemption'. It shows Harley Quinn trying to break free from the Joker's influence and finding an unexpected ally in Batman. The story is full of action and emotional moments.
In a fanfiction about Batman getting Harley Quinn pregnant, it could start with Harley Quinn realizing she's pregnant. She might initially keep it a secret from Batman, but then eventually tell him. Batman would be shocked and might not believe it at first. The story could then focus on how they both adapt to the situation. Harley Quinn could try to get away from her criminal past, while Batman would need to figure out how to protect her and the unborn child from his enemies. There could be a lot of character development as they both struggle with this new reality and how it fits into the world of Gotham they know.