Well, obviously Harry Potter is one of the main characters. And then there are the Marauders: James Potter, Sirius Black, Remus Lupin, and Peter Pettigrew. They are central to the story as it's about Harry meeting them.
One interesting plot could be Harry time - traveling and getting to join the Marauders on one of their pranks at Hogwarts. He might learn some new spells and mischief - making techniques from them.
Maybe Harry finds himself in a situation where he has to team up with the Marauders to fight a common enemy that was previously unknown in the original Potter story. This would create a whole new dynamic and show how different generations of Hogwarts students can work together.
There could also be some minor characters from the Marauders' era that might become more prominent. For example, Lily Evans, Harry's mother. Her relationship with James and how she might interact with Harry in this strange time - traveling or spirit - meeting scenario could be really interesting. And then there are the Hogwarts professors from both eras that could be involved, like Professor McGonagall, who could either be a guiding force or be a bit skeptical of Harry's new interactions.
Perhaps a plotline where the Marauders' spirits or echoes are awakened in Harry's time at Hogwarts. They start guiding him in his fight against Voldemort. They teach him spells and strategies that they used during their own battles against the Dark Arts. This would give Harry an edge and also create some really heartwarming and funny interactions as he tries to keep their presence a secret from his friends.
In some fanfictions, other characters like Dumbledore might also play important roles. He could be the one who arranges the encounter between Harry and the Marauders, either knowingly or unknowingly. And Hermione and Ron might also be involved in some cases, perhaps helping Harry understand the implications of meeting his father and his friends from the past.
The interactions might start with a lot of questions. Fred would be curious about the Marauders' time, and they would be interested in his more recent Hogwarts experiences. For example, Fred could ask about how they managed to create the Marauder's Map, and the Marauders could ask about the Weasley twins' joke shop ideas.
Well, obviously Petunia is one of the main characters. She is Lily's sister and has a complex relationship with the wizarding world. Then there are the Marauders - James Potter, Sirius Black, Remus Lupin and Peter Pettigrew. Each of them has their own distinct personality. James is the confident and sometimes arrogant one. Sirius is the rebellious and charming one. Remus is the more reserved and intelligent one, and Peter is the rather meek and follower - type among them.
Well, the main ones are Draco Malfoy and Harry Potter. Draco, who has his own journey of redemption in some of these fanfics. Harry, who is always the key figure in any story related to Hogwarts. And then there are the Marauders. James, the confident and sometimes arrogant Gryffindor, Sirius, the rebellious and loyal friend, Remus, the calm and intelligent werewolf, and Peter, who adds an element of mystery and betrayal.
Another plotline could involve Petunia getting involved in one of the Marauders' adventures by accident. Maybe she stumbles upon them while they are exploring a secret part of Hogwarts and has to work with them to get out of a tricky situation.