In some fanfictions, Harry travels back to the time of the founders of Hogwarts. This allows for a whole new set of interactions. He could learn the purest forms of magic from the founders themselves. Maybe he helps Gryffindor and Slytherin resolve their differences, which would have a huge impact on the future of Hogwarts. He could also introduce modern ideas of equality and justice among the students in that era, which would change the course of wizarding history and how Hogwarts functions.
A common plot in adult Harry Potter time travel fanfiction is that Harry goes back in time to give himself better training. He realizes in his original timeline that he was not fully prepared for the battles against Voldemort. So, he travels back to learn more advanced magic from the likes of Dumbledore or other powerful wizards much earlier. This not only changes his own capabilities but also has a significant impact on the events that unfold in the wizarding world. He might also use this new - found knowledge to better protect his friends and allies from the start.
One popular plot is Harry traveling back to his early Hogwarts years to prevent certain tragedies. For example, he might try to stop Cedric's death or Sirius's demise. Another plot could involve him going back to change the way Voldemort rises to power, perhaps by interfering with the Horcrux creation. Some fanfictions also have Harry traveling back to fix his relationship with his parents or other loved ones, like making sure his parents survive the first encounter with Voldemort and having a proper family life.
A common plot is Draco going back in time to fix his mistakes. For example, in many fanfictions, he tries to avoid getting involved with the Death Eaters in the past, knowing the consequences it will bring in the future. This often leads to him having to interact with a younger Harry Potter in new ways.
Well, in some older Harry Potter time travel fanfiction, the plot might involve Harry traveling back to his own past to fix his mistakes. He might have regrets about how he treated certain people or how he made certain decisions. So, he goes back to make amends. This can lead to some really heartwarming and also tense moments as he tries to change things without causing more harm. For instance, he might go back to when he first met Hermione and be nicer to her from the start. This can then change their relationship in unexpected ways throughout the story.
Well, a common plot involves the characters swapping places. Luffy ending up in Hogwarts and having to deal with magic lessons while Harry finds himself on the Thousand Sunny. Also, there are plots where they team up to solve a common threat that endangers both their worlds, like a new dark magic that spreads to the One Piece world.
A creative plot is when a character travels back to stop Voldemort from ever being born. This completely changes the whole dynamic of the wizarding world. It's different from the original story and allows for a whole new exploration of the characters and their relationships without the main threat of Voldemort.
A plot that I find very intriguing is when a character travels back in time to prevent the death of a loved one. For example, in some fanfics, Harry travels back to save Sirius. This creates a lot of tension as he has to deal with the time - turner rules and the possible consequences of changing the past.
A plot could be that James Potter travels back to the time when Voldemort was still Tom Riddle at Hogwarts. He could try to influence Riddle in a positive way, perhaps by befriending him and showing him a different path than the dark one. However, he has to be careful not to change the future too much or risk endangering his own existence and that of his family.
Another theme is exploring relationships. Since the Marauders are such a tight - knit group, fanfictions might explore how time travel affects their friendships. For example, how a new character from the future might impact the dynamics between Sirius, Remus, James, and Peter. It can also explore romantic relationships in a different time period.
Harry Potter himself is often a central character in these fanfictions. His journey through time to fix things or gain more knowledge is a common plot. Hermione is also popular as she's the brains and could potentially figure out the complex mechanics of time travel. Another popular character is Draco Malfoy. Writers like to explore his character in different scenarios, especially if time travel allows him to have a different relationship with the other characters.
One interesting plot could be a character going back in time to prevent Voldemort's first rise to power. They could try to change the events that led to his initial gathering of followers. Another plot might involve a time - traveling student who accidentally alters the sorting of the houses, causing chaos and new alliances within Hogwarts. And a third could be a time traveler going back to the Marauders' era and getting involved in their pranks and adventures, which in turn has unforeseen consequences for the future.
One interesting plot could be the characters going back in time to prevent certain dark magic events from ever happening. For example, they might stop Voldemort's rise to power much earlier in history.