In some fanfictions, there might be new vampire or werewolf characters introduced specifically for the story of Bella's little sister. These characters could be from other clans or packs and bring in new elements of conflict or cooperation. For example, a vampire from a far - away clan who comes to Forks seeking Bella's little sister because of a prophecy.
There could be other minor characters from Forks that get more spotlight in these fanfictions. For instance, the classmates of Bella's little sister who start to notice that there's something strange about her. They might become curious and start to dig deeper into the secrets of the town, which then draws in the vampires and werewolves.
Some fanfictions might introduce new characters that become popular. For instance, a new vampire who befriends the little sister. This vampire could have a different set of powers or a unique backstory that makes them stand out. Also, other members of the Cullen family, like Alice, could have a closer relationship with the little sister in the fanfiction, which makes her a popular character in this new narrative.
One common theme is family dynamics. Since it's about Bella's sister, it often explores how the sister fits into the family structure, especially with Bella being so central in the original Twilight story. Another theme is love triangles. Just like in the original, but now with the sister involved in some way.
A common trope is the twin having a different supernatural ability. For example, she might be able to control the elements while Bella has her mind - shield. Another is the love triangle, but instead of Edward - Jacob - Bella, it's between different characters involving the twin. Often, the twin also has a secret she's keeping from Bella which drives the plot.
Love and friendship are also common themes. The baby sister may find love among the supernatural beings or form strong friendships. For example, she could become friends with some of the werewolves while also having a connection with the Cullens. It adds a new layer to the existing relationships in the Twilight world.
Well, in some of these fanfictions, Bella's little sister might have unique powers. For example, she could be able to communicate with animals in a way that no one else in the Twilight world can. This would lead to all sorts of adventures, like helping the Cullens avoid danger by getting warnings from forest creatures.
Another plotline could revolve around her relationship with Bella. For example, she might be jealous of Bella's relationship with Edward at first but then come to understand and support it. She could also have her own love interest within the Twilight universe, perhaps a new vampire or werewolf character that was introduced just for the fanfiction.
There could be original characters created specifically for the fanfiction. For example, a magical creature that befriends Natsu's little sister and helps her on her journey. But the core Fairy Tail characters usually play important roles as well. They are the ones who provide the familiar backdrop of the Fairy Tail world that the story is set in.
Temari and Kankuro, Gaara's siblings, are likely to be in the fanfiction as well. They could play protective roles towards their little sister, or they might have some conflicts with her as she tries to assert her own identity. And there could be some antagonists, like rogue ninjas from other villages who see Gaara's sister as a target for some reason.
Obviously, Gohan and his sister are common characters. Goku might also be there as their father. Vegeta could be included too, as he is often part of the Dragon Ball storylines. Maybe Piccolo as well, since he has a connection to Gohan.
Often, you'll see Edward in these fanfictions. Even though the story is about Bella as a vampire before Twilight, Edward still plays a role. Maybe he's a mystery to Bella at first, or he's from a different vampire group that she has to interact with. Another common character is Jacob. He could be in a more antagonistic role, being jealous of Bella's new vampire life. And of course, the Cullens might be mentioned or even play a part. Carlisle could be a figure that Bella looks up to for advice on being a 'good' vampire.