Well, a possible plot could be that they marry as a political move in the supernatural world. Klaus, being a powerful vampire, and Bonnie, a strong witch, their union could shift the power balance. Then, they might face challenges from other supernatural factions who oppose their union. Also, a plot where they get married due to a magical bond that was accidentally created, and they have to figure out how to make their relationship work while dealing with their own personal issues and the reactions of their families and friends.
Their relationship could develop with a lot of power struggles at first. Bonnie is used to being independent and Klaus is used to being in control. But over time, they might learn to respect each other's strengths. Maybe they start to combine their magic and vampire abilities for different purposes.
One possible plot could be that Klaus believes Bonnie has the key to a powerful spell that could help him gain ultimate power. So he kidnaps her. He whisks her away to a remote island. There, he tries to persuade her to help him, using both threats and false promises. He might start off being cruel but then gradually start to have some strange respect for her as she resists him.
The main characters are Bonnie, a witch with great power and a kind heart deep down. Klaus, an Original vampire who is both feared and respected in the supernatural world. Their baby is also a main character, which is the focus of the fanfiction. There might also be other supporting characters like Damon and Stefan from the Vampire Diaries universe who could interact with Bonnie and Klaus regarding the baby. They might be curious, or they might be worried about the implications of this new addition to the supernatural world.
A memorable moment in some fanfictions is when Bonnie first realizes that Klaus isn't just a one - dimensional villain. This realization often leads to a shift in their dynamic and makes for some really interesting character development.
There's 'Bonnie's Choice' where Bonnie has to make decisions that involve Klaus in a complex web of supernatural politics. It delves deep into her character and how she copes with Klaus's presence. This story is interesting as it shows a different side of their relationship compared to the show.
The popularity of 'klaus obsessed with bonnie fanfiction' might be due to the contrast between their characters. Klaus is often portrayed as a powerful and sometimes villainous character, while Bonnie is a strong - willed witch. The idea of him being obsessed with her creates an interesting power dynamic and a lot of potential for complex relationships.
Another theme is the protection of the unborn child. Given the dangerous supernatural world they live in, both Bonnie and Klaus are usually depicted as being extremely protective. They will go to great lengths to keep their baby safe from all the threats out there.
You can try searching on fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions from various fandoms, including ones related to Klaus and Bonnie. Just type in 'Klaus and Bonnie baby' in the search bar, and it should show you relevant stories.