Obviously, Naruto is the central character. His relationship with the Nine - Tailed Fox is the core of this kind of fanfiction. The Fox itself, which is a powerful and mysterious entity within Naruto's body, is also a key character.
Sasuke may also be included. His relationship with Naruto is complex. In a jealous Fox fanfiction, Sasuke might unknowingly be involved in the situation that makes Naruto jealous. Maybe the Fox seems to react differently to Sasuke's chakra, and Naruto's jealousy flares up, leading to some interesting interactions between the three of them.
The Joker himself is obviously the main character when it comes to his jealousy. Harley Quinn is often involved as she has a complex relationship with the Joker. Batman can also be part of the story in some cases. For example, if Batman is seen as a rival for Harley's attention in a strange way, the Joker might get jealous. Even though Batman is his enemy, the idea of Harley being interested in Batman in any way could trigger the Joker's jealousy.
Well, often it's Clary, Jace, and Simon. Simon is Clary's best friend, and in some fanfictions, his relationship with Clary can make Jace a bit jealous, but at the same time, if Simon seems too friendly with another girl, Clary might also get jealous in a different way. It's an interesting triangle - like situation that can add a lot of drama to the fanfiction. And of course, Magnus Bane might also make an appearance and his flamboyant personality could somehow be involved in situations that lead to Clary's jealousy.
Well, the main characters are obviously Bella and Edward. Bella is the one who tries to make Edward jealous, usually by getting close to other male characters. Edward is the one who gets jealous because of his deep love for Bella.
Often, the main characters are Naruto and his friends. Naruto, as the protagonist, is naturally drawn to the mystery of the egg. His friends like Shikamaru, who is intelligent and can strategize about how to deal with the situation regarding the egg, and Choji, who might provide some physical protection if needed. Hinata could also be involved, perhaps having a special connection to the egg because of her Byakugan. And then there are the villains, like the members of the Sound Five, who might want to get their hands on the egg for their own evil purposes.
Naruto himself is almost always involved as he is the main character of the Naruto series. His friends like Sasuke and Sakura may also be part of the story. Sometimes, even villains like Orochimaru or Madara could be involved if the plot of the fanfiction is related to a big threat where their knowledge or power is needed.
Obviously, Naruto himself is the central character as it's about him 'snapping'. Sasuke is also often involved. He might be a factor in what causes Naruto to snap, or he could be on the receiving end if Naruto's snapping is directed at his actions or decisions.
In 'naruto angry fanfiction', characters like Hinata can also be involved. If she is in danger or if Naruto feels that he couldn't protect her well enough, it can stir his anger. And villains like Orochimaru or Madara can be present as they are often the source of problems that make Naruto angry, whether it's through attacking the village or harming his friends.
Naruto is a must - have main character. In the fox family, there could be a powerful alpha - like fox that serves as a leader and mentor to Naruto within the family context. There may also be a fox cub that Naruto befriends and protects. Other than that, characters like Jiraiya might be involved as he was Naruto's teacher and could have some connection to the fox family lore. Plus, the nine - tailed fox itself could be a central figure in the family, with Naruto having a special bond with it.
The main characters are typically Naruto and the chibi fox. However, in some fanfictions, other characters from the Naruto universe might play important roles. For instance, Jiraiya could make an appearance. He might recognize the significance of the chibi fox in relation to some old ninja legends and guide Naruto in his relationship with the fox. This could add more depth to the story as Jiraiya imparts his wisdom and knowledge.
Harry Potter himself is the key character in 'Harry is burned' fanfictions. But other characters like the Weasley family as a whole can be involved. Mrs. Weasley might take on a motherly role towards Harry, trying to nurse him back to health. And Fred and George could use their magical inventions to try and ease Harry's pain or discomfort from the burns.