Obviously, Harry himself is the central character. Hermione is also often involved as she is Harry's friend. Ron too, as they are a trio. Dumbledore usually plays an important role as he is the headmaster. Snape is also a popular character in these fanfictions as Harry might try to change their relationship. And of course, Hagrid, who is always there for Harry in the original story and could be involved in new and different ways in the fanfiction.
In many 'Harry goes back to first year fanfiction', Neville Longbottom is a key character. Harry, with his future knowledge, might help Neville develop his magical abilities faster. Draco Malfoy is also often part of these stories. Harry could try to change Draco's attitude from the very beginning. And Filch, the caretaker, could be more involved as Harry might use his knowledge to either avoid getting in trouble with Filch or to help Filch in some way, which would be a unique twist in the story.
Luna Lovegood is also a popular character to be paired with Harry in these fanfictions. Her unique perspective and Harry's new - found knowledge from going back in time could lead to some really interesting adventures. They could discover new magical creatures or secrets about the wizarding world.
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.
Obviously, Severus Snape is the central character. He is the one who travels back in time, so all the actions and changes are centered around him. But other important characters often include Lily Evans. Since Snape had a deep connection with her, he might try to interact with her in different ways to change the past.
Well, of course, Ichigo himself is the central character. But Rukia also often plays an important role. Since she was the one who initially transferred her powers to Ichigo, in the time - travel scenarios, she might be involved in different ways. Maybe Ichigo goes back in time to save her from some danger she faced in the past.
Well, in many izuku goes back in time fanfictions, besides Izuku himself, his mother is an important character. He might go back in time to be a better son, protect her more, or even change things that affected her in the past. Another often - seen character is Aizawa. As Izuku's teacher, Izuku could use his time - travel knowledge to impress Aizawa earlier or get more help from him in his hero training. And of course, the villains like Shigaraki could also be involved. Izuku might try to stop Shigaraki from becoming a villain by going back in time and changing certain events that led to his fall.
Harry Potter himself is often involved. Writers might explore what would happen if he had more control over his powers from the start. Hermione Granger is also popular. She's known for her intelligence and control over her studies, so in fanfiction, she could be given even more control over magical knowledge or spells. Another one is Draco Malfoy. Fanfic writers might give him the ability to control his family's dark legacy and turn it into something positive, or he could be given control over some new form of magic.
Definitely Harry Potter himself can be a part of it. He might be learning to bake as a way to relax or bond with his friends. Luna Lovegood could also be in these fanfictions. She has a very creative and unique personality, so she could bring some really out - of - the - box ideas to the baking table. For example, she might suggest using ingredients that others would find strange but that end up creating a delicious and magical treat.
Draco Malfoy is frequently included as well. His family's dark arts tendencies make him a likely candidate to be involved with hexes, either using them for his own gain or getting caught up in a plot where he has to deal with the consequences of using or being affected by a hex.
Definitely Harry Potter. Fanfiction writers like to dig deeper into his family tree and uncover hidden bloodline secrets. Luna Lovegood can be a character in these fanfictions as well. Her unique personality and family background can add an interesting angle to bloodline exploration. Neville Longbottom is also a likely candidate. Given his family's history and his own growth in the series, exploring his bloodline in fanfiction can open up new storylines, like if there are undiscovered powers or connections in his family's bloodline.