I'm not sure specifically as it depends on the particular fanfiction. It could be the person who makes the wish, likely a human or some other sentient being. And of course, the dragon is bound to be a main character as the whole concept revolves around it.
In 'the wish of the dragon novel', the main characters could include the dragon of course. There may be a wizard or sorcerer who has some connection to the dragon's wish, either helping or trying to manipulate it. And perhaps a young adventurer who stumbles upon the dragon's situation and gets involved in the quest related to the dragon's wish.
I don't know for sure as I haven't read it. But it could be the dragon itself as the main character. There might also be characters like a human who befriends the dragon or other magical beings that the dragon encounters during its journey to fulfill its wish.
Since I don't know the exact 'a wish novel', I can't say for sure. But it could be a young protagonist who is on a quest related to wishes.
As I haven't read 'the wish novel', I can't be certain about the main characters. However, it's common in novels for there to be a central character who is on a journey, perhaps a person with a strong will and a big wish. There might also be supporting characters like family members or antagonists who oppose the main character's wish.
A young dreamer could be a main character. This person is always looking at the stars and has a big imagination. They are the one who first makes the wish upon a star and sets the story in motion.
A group of school kids could be the main characters. They all wish upon a star together during a school camping trip. Maybe one wishes for better grades, another for popularity, and so on. But their wishes start to mess with the natural order of things at school. So they have to work together to fix the chaos they've created, learning about friendship and the importance of being careful what you wish for along the way.
I don't have enough information to say who the main characters are in 'an unselfish wish fanfic'. It could be a young protagonist who is known for their kind heart and makes the unselfish wish. Or it could be an older, more experienced character who has seen the hardships in the world and decides to make a selfless wish.
Obviously, the boy is one of the main characters. There might also be his family members if the wish is related to them, like his parents or siblings.
Again, without knowing the specific 'The Wish Christmas Story', it could have characters like a young child as a main character. Often in Christmas stories, children are central as they are full of wonder and wishes during this time.
In 'the last wish novel', apart from Geralt, Yennefer and Ciri, there are other notable characters. Dandelion, for instance, is Geralt's friend. He is a bard and often gets involved in Geralt's adventures, sometimes causing trouble but also providing some comic relief. Another character is Vesemir, an older Witcher who serves as a mentor to Geralt and the other Witchers at Kaer Morhen.