What are some interesting plot ideas in 'Harry Potter goes back in time' fanfiction?

One idea could be Harry going back in time to his parents' era at Hogwarts. He could try to prevent certain events that led to their deaths. Another could be him going back to the time of the founders of Hogwarts and getting involved in the creation of the houses and Hogwarts' early rules.

One idea could be that baby Harry goes back to the time when his parents were at Hogwarts. He could accidentally change some small events that end up having a big impact on the future. For example, he might cause his parents to meet earlier or in a different way.

A cool plot twist might be that Fem Harry goes back in time and discovers that her parents were involved in a secret mission that was never revealed before. This could lead to her having to deal with the consequences of uncovering that truth. Also, she could find out that Voldemort had a different origin or a hidden weakness that was lost in history. As she tries to use this knowledge to defeat him earlier, she might face opposition from some of the older wizards who don't believe her or are afraid of the changes she could bring. It could also be that she changes the way magic is taught at Hogwarts, introducing new spells or techniques from the future that create a whole new set of challenges and opportunities for the students.

One plot idea could be that Ino goes back in time to the founding of Konoha. She could use her knowledge of the future to prevent some of the early tragedies that befell the village. Another idea is that she goes back to her own childhood and tries to change certain events that led to insecurities in her later life. For example, she might try to befriend Sakura earlier and avoid the rivalry that developed between them.

One idea could be that the vanguard goes back to a crucial moment in history and has to prevent a major disaster that would change the future in a negative way. For example, they could stop a powerful weapon from being created too early.

Pan could also go back in time to meet his younger self. He could give his younger self advice on how to become stronger and more skilled. However, this might have unforeseen consequences as changing his own past could disrupt the balance of his life in the present. He might find that some of the relationships he had in the present are now completely different because of the changes he made in the past.

One idea could be that Sasuke goes back in time and tries to prevent the Uchiha massacre. He could use his knowledge of the future to stop Itachi from carrying out the order. Another could be that he goes back to his early days at the ninja academy and tries to change his relationship with Naruto from the start. Maybe he would be more open and friendly, which could change the whole dynamic of their rivalry.

Well, in this type of fanfiction, Obito might go back in time and focus on changing his relationship with Rin. He could try to be more open and honest with her, which might change the whole dynamic of their triangle with Kakashi. He could also use his future knowledge to gain more power earlier, perhaps by seeking out different jutsu or training methods that were not available to him the first time around. This could lead to him becoming a more powerful ninja much sooner and changing the course of the ninja world.

Another plot could be that they go back to a time when a great ninja war was about to start. Team 7 could try to prevent the war by changing certain key events or by uniting the warring factions. They might use their skills and knowledge from their own time to broker peace deals and stop the bloodshed before it begins.

One idea could be that Bill goes back to a time when the Losers' Club first formed and tries to befriend them in a different way, perhaps to change their perception of him from the start. Another could be Bill going back to a time before Pennywise arrived in Derry and trying to prevent the events that led to the town's curse.