Castiel is a beloved character too. His angelic nature combined with his growing humanity makes for great fan fiction material. Regarding 10x5, a story could be written about how Castiel uses his powers in a new and unexpected way to help Sam and Dean deal with the situation they were in during that episode.
Dean Winchester is always a popular choice. His complex personality, his love for his family, and his struggles with his inner demons make him a fascinating character to write about. In the context of 10x5, you could explore his reactions to the events more deeply, or create a side story about his past that relates to what happened in that episode.
Kazuki is often a popular choice. His complex personality and his relationships with other characters, especially his interactions with Mariya, offer a lot of material for fan fiction writers. Writers can explore his inner thoughts and feelings more deeply in their stories.
Popular characters in Stranger Things 2 fan fiction include Eleven. Her backstory in the lab, her search for identity, and her relationships with the boys are all rich areas to write about. Dustin is also a favorite. His unique personality, his pet D'Artagnan, and his role in the group's adventures offer many story possibilities. Then there's Joyce. Her determination to protect her children and her ability to sense the Upside - Down makes her an interesting character to write about in fan - made stories.
Max Murphy is often a popular choice. He's the main character in the original, and there are so many aspects of his character that can be explored further in fan fiction. His growth throughout the story, his relationships with other characters, and his adventures are all ripe for expansion.
Love interests in the story are also popular. Writers can explore the relationships between characters in more depth. They can create more romantic or tense moments between the love interests, adding more emotional depth to the fan fiction.
The village elder is often a popular character to write about. They usually have a wealth of knowledge and experience, and their decisions can greatly impact the village. Writers can explore their past, their hopes for the village's future, and the secrets they might be hiding.
Sylvanas Windrunner is quite popular. Her complex character arc, from being a high elf ranger to the banshee queen, gives a lot of room for exploration. Arthas Menethil is also a favorite. His fall from a noble paladin to the Lich King is a tragic and fascinating story. And Thrall, as he was such an important figure in uniting the Horde and had a strong sense of leadership and honor.
Beaver is definitely a popular character to write about. He's the central figure of the show, and his innocent and curious nature gives a lot of room for different storylines. Writers can explore his growth, his dreams, and his interactions with his family and friends.
Definitely Sam and Dean Winchester. They are the heart of the show. In fanfiction for 12x19, their reactions to the events in the episode can be explored in many different ways. Castiel is also very interesting. His angelic nature and his relationship with the Winchesters always offer a lot of material for writers. And Crowley, with his complex personality and his own motives, can be a great character to write about in the context of this episode.
Owen is also a favorite. His goofy and friendly nature makes him easy to write in various situations. He can be the comical relief in a serious plot or be part of a heartwarming friendship story.
Cecil is definitely one of the most popular. His journey from a Dark Knight to a Paladin is full of potential for further exploration. Rosa is also popular as she is Cecil's love interest and has her own powers as a white mage. Kain is another character that many like to write about, especially his complex relationship with Cecil and his struggle with Golbez's control.