What could be the possible content of Harry's secret fanfiction?

It could also be a story that delves into Percy's past. There might be some events from his childhood or early days that he has never shared. The fanfiction could be a creative exploration of those untold stories, including his relationships with his family or how certain experiences shaped him into the person he is now.

It could be some personal achievements that the person doesn't want to share publicly yet. For example, getting a job offer but waiting for the right time to announce.

Maybe the secrets could be about their pasts, like some hidden magical abilities they had before coming to Hogwarts. For example, a professor might have been part of a secret magical society in their youth and that's a big secret.

It could be about a hobbit's hidden adventure that was not part of the original story. Maybe the hobbit discovers a magical artifact in a forgotten corner of Middle - earth and has to keep it a secret while trying to figure out its power.

Perhaps it's a story where Lucy is in love with someone she can't be with publicly. So she writes this secret fanfiction to express her feelings and desires about that relationship.

It could be about some dark and dangerous secret that the father has been hiding throughout his life. Maybe it's a crime he committed in the past, like a theft or something more serious.

It could be about some dark family secrets that the father has been hiding all his life. Maybe it involves a past crime or some deeply buried family shame.

One possible plot could be that Harry is a unique creature himself, perhaps a hybrid of some sort. He has the ability to lay eggs which are the key to saving his species. He embarks on a journey to find a safe place to hatch these eggs because there are villains who want to destroy them. Along the way, he meets friends who help him protect the eggs and in the end, he successfully hatches them and restores his species.

In some fanfictions, it could be a character from another magical school. Like a girl from Beauxbatons or Durmstrang. She might have met Harry during an international magical event and they've been secretly seeing each other ever since.

Maybe it's about the wacky and unpredictable nature of Dada magic. He could be sharing some of the most absurd spells or magical concepts that are unique to Dada.