Well, in such a fanfiction, Petunia might finally come to terms with Harry's wizarding world. Maybe she starts to see the magic in a new light and reconciles with the fact that her sister was a witch.
Obviously, Petunia is one of the key characters. Then there's Harry, as it's about her meeting his family. And members of Harry's family like his parents, James and Lily, would also be important even if they might be in memories or magical apparitions.
Well, it depends on the specific fanfiction. Some fanfic authors like to play around with the relationships and concepts in the Harry Potter universe. So it's possible that in certain fanfictions, Petunia is Harry's pet. However, in the canon story, Petunia has a very different role as Harry's rather unfriendly aunt who begrudgingly takes him in. But fanfiction allows for all kinds of creative interpretations.
In a fanfiction where Petunia meets Sirius, it could be a very interesting encounter. Sirius, being a wizard from the wizarding world, might shock Petunia at first. He could show her some simple magic, like making a flower bloom, which would both terrify and fascinate her.
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.
One great Petunia fanfiction could be one where she has a moment of self - realization. Maybe she discovers some of Lily's old magic things and starts to understand the wizarding world better. It could show her in a more sympathetic light, perhaps she even tries to protect Harry in her own way.
One of the most interesting scenarios could be when Petunia and Sirius are forced to team up for a common goal, like protecting Harry from a new threat. Petunia would have to rely on Sirius' magic skills, and Sirius would have to trust Petunia's knowledge of the Muggle world. Their interactions during this time would be full of tension, misunderstandings, but also potential for growth and understanding.
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.
Well, Petunia can be really well - written. If the author delves into her insecurities and jealousy towards Lily, and then shows how she reacts to James, it can create a very complex and interesting character. For example, a good fanfiction might show Petunia's internal struggle when she sees James' charm and popularity.
One possible plotline could be that Petunia initially hates James but then gradually discovers his good side. Maybe through some accidental encounters where James shows his kindness and courage, Petunia starts to question her long - held prejudices against him.