One interesting plotline could be Bella's struggle to control her new vampire instincts while still maintaining her relationships with her human friends and family. For example, she might have a hard time being around them without revealing her new nature.
Often, there's a plotline centered around the baby's future. Will it be a normal vampire? A hybrid with unique powers? The fanfiction might explore how Bella and the others prepare for the baby's arrival, including things like finding a safe place to give birth. And there could be a plotline about the baby being a symbol of hope or a threat, depending on different characters' perspectives.
Another plotline could involve Sookie using her new vampire powers to solve mysteries in the supernatural world. Since she already had some unique abilities as a human, becoming a vampire could enhance them and make her a sort of detective in the vampire community.
Edward is almost always there. Since he's such a central figure in Bella's life as a human and vampire in the original story, he would likely play a big role in the fanfiction too. He might be the one guiding Bella through her new vampire life.
In some 'Bella Swan as a Vampire' fanfiction, a great plotline is her exploration of her new vampire senses. She could find that her sense of smell leads her to discover things about the past of the places she visits. And in terms of relationships, her bond with Edward could change in a really interesting way. Since they are both vampires now, they might have different power dynamics and new challenges in their relationship. For instance, they could compete in terms of their vampire skills, which could either strengthen or strain their relationship.
One possible plotline could be Bella adjusting to her new vampire abilities. For example, she might struggle with her increased strength at first and accidentally break things. Another could be her relationship with Edward changing as they are now both vampires. Maybe they have newfound understanding and experiences to share.
One interesting plotline could be Natsu trying to adjust to the new physical form while still having the same adventurous spirit. For example, Natsu might initially struggle with wearing different types of clothes that are more suitable for a female body. Another plotline could be how Natsu's friends react. Some friends might be shocked at first, but then quickly accept and help Natsu through this strange transformation. There could also be a plotline where Natsu discovers new abilities or sensitivities that come with being in a female form.
Well, there could be a plotline where Castiel in dog form gets adopted by a family. He has to balance living as a normal dog in a human household while also trying to figure out how to reverse the spell or whatever caused him to turn into a dog. This could involve him protecting the family from supernatural threats that they are unaware of, all while being a cute furry companion.
A great plotline could be the mystery behind who turned Hermione into a baby. It could be a dark wizard trying to stop her from achieving something in the future. As a baby, Hermione might start showing some unusual magical abilities that she didn't have before, which could attract the attention of both good and bad forces in the wizarding world. And her friends would be in a race against time to protect her and find a way to turn her back.
Perhaps there's a plotline where the transformation into a ferret has some unforeseen side effects. For example, Harry might gain some ferret - like abilities such as enhanced sense of smell or speed, which he then uses to his advantage in solving a mystery or escaping from a dangerous situation in Hogwarts. He could also struggle with some of the more ferret - like instincts, like being tempted to hoard shiny objects.
One possible plotline could be the reader, now a vampire, struggling to adapt to the vampire society in the Twilight universe. For example, dealing with the strict rules of the Volturi. Another could be falling in love with a character from the original series, like Edward or Jacob, but facing new challenges due to being a newly - turned vampire.