It's hard to say exactly. But it might cause the Doctor's personality to change or give them new abilities and challenges to overcome. It all depends on the author's imagination!
In this fanfiction, after Stiles gets bitten by a vampire, he might find himself in the middle of a vampire war. The vampire who bit him could belong to one faction, and now the other faction sees Stiles as a threat or a tool. He has to learn about vampire politics and hierarchies quickly. His friends, especially those who know about the supernatural, would try to protect him. Stiles would also have to deal with the physical and emotional changes that come with being a vampire, like the isolation that can come from living a nocturnal life and the fear of hurting those he loves.
In the 'Harry Potter gets bitten by a vampire' fanfiction, there are numerous possibilities. Harry's appearance might change, with paler skin and perhaps sharper features. His magical abilities could be affected in strange ways. For example, his Patronus might change form due to his new vampiric nature. He could also form new alliances with creatures that are more accepting of vampires, like some werewolves who might see him as a kindred spirit in a way. This could create a rift between him and some of his old friends who are more traditional in their views of the wizarding world, but it could also open up new opportunities for him to explore different aspects of magic and the supernatural that were previously hidden from him.
Often, when a girl gets bitten by a vampire in a cartoon, she'll experience strange cravings and start to notice changes in her appearance and behavior. She might also have to deal with the conflict of fitting into the vampire world or trying to return to normal.
His relationship with his friends would likely become more strained. They might be afraid of him or he might be afraid of hurting them. For example, his best friend Scott, who is also involved in the supernatural world, might be worried about Stiles losing his humanity.
Well, the comic nerd might develop vampire-like powers and start having strange cravings for blood.
When Carl is bitten in the comics, it's a heart-wrenching event. It forces the survivors to confront their fears and makes them question their future. It's a crucial plot development that sets the stage for many intense moments to come.
Another theme is the power struggle. The bitten character may find themselves in the middle of a power struggle between different vampire clans or factions. They have to decide which side to take or how to navigate the complex politics of the vampire world. It's often filled with intrigue and back - stabbing.
Often, when Rory is hurt in fanfiction, it triggers a series of events that test the relationships among the Doctor and the companions. It might also bring out hidden strengths or vulnerabilities in Rory himself.
Often, the story will focus on Hermione's struggle to come to terms with her new identity. She may try to find a cure at first. For instance, she might search through ancient magic texts in the library at Hogwarts.
One idea could be that Peter, now as a female, has to navigate the daily challenges of high school in a completely different way. Maybe she discovers new powers related to femininity that the male Peter didn't have. For example, she could have a heightened sense of intuition that helps her in battles or in understanding her friends' emotions better.