In addition to the trio, Severus Snape could be a key character. Given his complex relationship with Harry in the original series, in a 'harry goes crazy' scenario, Snape might be reluctantly dragged into helping or might be initially suspected of causing Harry's madness. And then there are the Weasley family members, like Ginny. She could be an important part as she has a special connection with Harry, and she would be extremely worried about him and try her best to support him.
Well, obviously Harry Potter himself is the central character. Hermione and Ron are almost always involved too. They would be the ones trying to figure out what's wrong with Harry and how to fix him. Dumbledore might also play a major role, as he often has deep knowledge about magic and could potentially help Harry regain his sanity.
Obviously, Harry Potter himself would be the central character as the title implies. Hermione and Ron would most likely be involved as well, since they are Harry's closest friends. They would probably be the ones trying to figure out what's wrong with Harry and how to fix him. Dumbledore could also play a big role, as he often has the wisdom and power to deal with strange situations.
Neville Longbottom can also be a main character in some 'Harry Potter goes back in time' fanfictions. Given his growth and importance in the original series, in the fanfic, Harry might go back and help Neville become more confident earlier. This could have a significant impact on the fight against Voldemort as Neville could then be an even more powerful ally from an earlier time.
Obviously, Naruto is the central character as the title 'naruto goes mad' implies. Sasuke often plays a crucial role too. He might be the cause of Naruto's madness in some cases, like if he betrays Naruto again in a more extreme way. Sakura could also be involved, perhaps trying to bring Naruto back from his madness. And Kakashi, as Naruto's former teacher, may try to figure out what's wrong with Naruto and find a way to help him.
Harry is the central figure. In addition to the well - known Camelot characters like Arthur and Merlin, Guinevere can also be a main character in some fanfictions. She could play a role in Harry's integration into Camelot society. There might also be some original characters created by the fanfiction author, like a young apprentice in Camelot who becomes Harry's friend and helps him understand the ways of Camelot. Another often - seen character is Morgan le Fay. She could be an antagonist to Harry, seeing his presence as a disruption to her plans in Camelot.
Obviously, Harry is one of the main characters. There could also be some original characters created specifically for the Salem setting, like a local witch who befriends Harry. And sometimes Hermione or Ron might make an appearance, especially if the story involves some sort of connection between Hogwarts and Salem.
Well, Harry is obviously one of the main characters. He's the one who is going to Harvard. There might also be some original characters created for the fanfiction. These could be Harry's classmates at Harvard, like a brilliant but eccentric roommate who helps Harry understand the ropes of the university.
Obviously, Harry Potter himself is a main character. Hermione and Ron often play important roles too. They might try to break Harry out of Azkaban or help him from the outside. Sometimes, Sirius Black could also be involved, especially if the story is related to the secrets of Azkaban or the wrong imprisonments. Dumbledore could also be a key figure, guiding Harry or influencing the events from afar.
Dumbledore's character often plays a role. He might be a guiding figure in the background, even if Harry is going against his wishes. And there could be new characters introduced, such as other outcast wizards or witches who Harry meets during his travels.
The main characters are Sam and Dean Winchester, of course. But in some fanfictions, Bobby Singer might also be involved. Since he was like a father figure to them, he could be the one guiding them through the time - travel process, or he could be there in the past waiting for them. Also, the characters of their parents, Mary and John Winchester, might show up if they go back to a time when their parents were alive.
Obviously, Harry Potter himself is the central character as it's about him in diapers. Dumbledore often features as he plays a crucial role in Harry's life. Hagrid might also be there as he has a special connection with Harry. And of course, the Dursleys could be part of the story, perhaps in their begrudging care of baby Harry.