Maybe the Dementors somehow find their way into Neverland. Harry, with his experience in dealing with them, teams up with Peter Pan to fight them off. Peter's ability to fly and his sense of adventure could add a new dynamic to the fight. Also, the Lost Boys could be fascinated by Harry's magic wand and the spells he can cast.
One idea could be that Peter Pan takes Harry Potter to Neverland to escape from Voldemort. In Neverland, Harry discovers new magical abilities that are different from those in the wizarding world. He could learn to fly in a more carefree way like the Lost Boys and use his magic in new and exciting environments.
Another idea is a crossover with The Chronicles of Narnia. Peter could enter Narnia through some magical portal. He'd interact with the talking animals and the Pevensie children, and his skills in fighting pirates could be useful in Narnia's battles.
One idea could be that Harry Potter somehow gets transported to Neverland. He could teach the Lost Boys some magic, and they in turn could show him how to have fun in a more carefree way than at Hogwarts. Another idea is that Peter Pan visits Hogwarts and causes chaos with his flying and mischievous nature among the students and professors.
One idea could be that Peter Pan and his Lost Boys end up in a different Disney world, like the world of Beauty and the Beast. They might mistake the Beast for a new kind of pirate or monster at first. Another idea is that a Disney princess, say Cinderella, gets whisked away to Neverland by Peter Pan. She could teach the Lost Boys some manners while they teach her how to have more fun. Also, Tinker Bell could get jealous of a new Disney character who catches Peter Pan's attention, like Ariel from The Little Mermaid.
One possible plot could be that Peter Pan takes Harry Potter and his friends to Neverland. There, they encounter the Lost Boys and Tinker Bell. Harry discovers new magic in Neverland that's different from Hogwarts magic. They could also face a common enemy, like a dark force that's trying to take over both Hogwarts and Neverland. The wizards could teach the Lost Boys some basic spells, and in return, the Lost Boys could show them how to fly better than on broomsticks.
Well, you could write a fanfiction where Peter Pan and Wendy grow up but still remember their adventures in Neverland. They could try to recreate that sense of magic in the real world, perhaps by opening a place where children can experience a bit of Neverland. Or, what if a new villain emerged in Neverland and Peter and Wendy had to team up in a different way than before to defeat them? They might have to use Wendy's more grown - up thinking and Peter's knowledge of Neverland's secrets.
One interesting concept could be the interaction between magic in the Harry Potter world and the Neverland magic in Peter Pan's realm. For example, how would a Hogwarts student react to flying without a broom in Neverland? Another concept might be the characters' crossovers. Imagine Harry Potter and his friends meeting Peter Pan and the Lost Boys. They could learn different survival skills from each other, with Harry's group teaching about potions and spells, and Peter Pan's group showing how to live freely in the wilds of Neverland.
I think Harry Potter himself would be very interesting. Imagine him in Neverland, a place so different from Hogwarts. He could bring his courage and sense of justice from the wizarding world and apply it in the new setting. His magic skills would also be fascinating to see in the context of Neverland, like how he would use spells against the likes of Captain Hook or other threats there.
Well, you could write a fanfiction where Peter Pan loses his ability to fly and Wendy has to help him find a way to regain it. It could involve them going on a journey across Neverland, facing various challenges and meeting new characters along the way. They might have to seek the help of the mermaids or the Lost Boys. This would not only test their friendship but also show their growth as characters.
Perhaps in the fanfiction, Peter Pan gets injured during one of his battles with Captain Hook. Jane, who has learned some basic first - aid skills from her own world, takes care of him. This leads to a deeper bond between them, and Peter starts to see Jane in a new light, not just as a visitor to Neverland but as a true friend and an equal.
One idea could be exploring Wendy's life back in London after her adventures in Neverland. Maybe she's having a hard time adjusting and misses Peter terribly. Another could be a story where Peter brings some of the Lost Boys to London for a visit and the chaos that ensues. A third idea might be a tale where Wendy's younger siblings grow up and start to doubt the existence of Peter Pan, but Wendy has to convince them he's real.