There could be a female werewolf character who falls in love with one of the Supernatural characters. This would add a romantic sub - plot to the fanfiction and also create a lot of drama as they try to navigate their different worlds and the prejudices that come with being a werewolf and a hunter.
A popular character could be a half - werewolf, half - hunter. This character would be constantly torn between their two natures, and in a crossover, they could be a bridge between the werewolf community and the hunters in Supernatural.
Another character might be an alpha werewolf who decides to make a deal with the Winchesters. This alpha could have its own motives, like protecting its pack from a greater threat that the Winchesters are also after.
One idea could be a story where a werewolf from the werewolf lore gets caught in the middle of a Supernatural's Winchester brothers' hunt. Maybe the werewolf has information about a powerful demon they are chasing.
Well, obviously Bella herself is a central character. Jacob is also very popular as he is a werewolf in the original story and often has a complex relationship with Bella in the fanfiction. Then there are the other members of the wolf pack like Sam and Seth. They can play important roles in Bella's new werewolf life, either as mentors or as friends who help her adapt to her new identity.
One popular supernatural crossover fanfiction involves 'Supernatural' and 'Doctor Who'. In this type of story, the Winchester brothers might team up with the Doctor to fight against a common supernatural threat that spans across different universes. It combines the dark, monster - hunting world of 'Supernatural' with the time - and - space - traveling adventures of 'Doctor Who'.
One popular character could be the girl who befriends the werewolf boy. She often serves as the connection between the werewolf boy and the human world. Another might be the werewolf boy's mentor or an older werewolf who teaches him about his heritage. And sometimes, there's a villain, like a hunter who is after the werewolf boy, which adds conflict to the story.
Luna Lovegood is often reimagined as a female werewolf in some fanfictions. Her unique personality and the way she views the wizarding world adds an interesting twist when she is given the werewolf trait. Writers explore how she copes with her new identity and how it affects her relationships with other characters like Harry and Hermione.
Lady Ashbury from Vampyr could also be a great character for crossovers. She is powerful and mysterious. In a crossover with Castlevania, she could either be a powerful force against Dracula or perhaps have some hidden connection to him that could be explored. Her knowledge of the vampire world in Vampyr could bring new perspectives to the Castlevania universe.
Some fanfictions might pair Castiel and Cisco Ramon. Castiel's otherworldly nature and Cisco's scientific mind could lead to some really interesting interactions. For example, Cisco could be fascinated by Castiel's angelic powers and try to find a scientific explanation for them, while Castiel could be intrigued by Cisco's tech - savvy ways.
Common themes include transformation. The process of turning into a werewolf, and how it affects the character both physically and mentally. There's also the theme of secrecy. Werewolves usually have to keep their identity a secret from humans, and this secrecy can lead to all sorts of plot twists. Power struggles within the werewolf hierarchy are also common. Alphas fighting for control, and betas trying to rise in the ranks.
I would recommend 'The Werewolf's Secret'. This fanfiction focuses on a werewolf who has to hide his true identity in a world full of supernatural hunters. It's full of action and suspense, and the relationship between the werewolf and the other supernatural beings in the story is quite complex and interesting.
Sam and Dean Winchester are always popular in Supernatural fanfiction, including those based on 13x17. Their brotherly bond and their roles as hunters are often central to many stories. Castiel is also a favorite. His angelic nature and his relationship with the Winchesters make him a great character to write about in relation to the events of 13x17.