In a Naruto and Tinkerbell crossover fanfiction, Naruto could be shrunk down to fairy size and have to adapt to the rules of Pixie Hollow. He'd be the odd one out with his ninja abilities. Tinkerbell might be curious about his chakra and how it works. Together, they could form an unlikely friendship and team up to solve problems that neither could handle alone, like a dark force that is draining the magic from Pixie Hollow and Naruto's world.
It could be an evil ninja who has learned to use dark magic and wants to take over Pixie Hollow for its magic. He sees the fairies' magic as a source of power to enhance his own dark jutsu.
One idea could be that Tinkerbell finds her way into the wizarding world of Harry Potter. Maybe she gets accidentally transported there by some magical mishap. She could use her fairy magic in Hogwarts, like helping to repair broken objects in a more sparkly and unique way compared to the Reparo charm.
A possible plot could be that there is a competition in Pixie Hollow, and Naruto is brought in as an unexpected contestant. Tinkerbell is assigned to be his guide. They have to complete various tasks that require both Naruto's combat skills and Tinkerbell's knowledge of the local magic. As they progress through the competition, they face challenges that test their friendship, and by the end, they've created a new type of harmony between their two very different worlds.
A Tinkerbell crossover with the Little Mermaid could be really cool. Tinkerbell could visit Ariel underwater. She might help Ariel find some really special treasures that only a fairy can see. Or perhaps a crossover with Cinderella. Tinkerbell could use her magic to make Cinderella's dress even more beautiful for the ball. And she could also help Cinderella outwit her step - sisters and step - mother with her fairy tricks.
If it's a crossover with Alice in Wonderland, the Queen of Hearts could be the main antagonist. The Queen might see Tinkerbell as an intruder and try to behead her. Tinkerbell would have to use her wits and magic to survive in the crazy world ruled by the Queen of Hearts.
Tinkerbell could be a new kind of magical creature in the wizarding world. She might be discovered by Hagrid in the Forbidden Forest. Since she's so small, at first the wizards might mistake her for a really tiny pixie. But then they'd realize she has different powers, like being able to create light and fix things with her fairy dust.
One possible plot could be that Tinkerbell gets jealous when Peter Pan brings a new friend from another world to Neverland. She tries to play tricks on the new friend but accidentally endangers all of Neverland. Then she has to team up with the new friend to save Neverland and in the process, she and the new friend become closer, while Peter Pan learns a lesson about friendship and jealousy.
I'm not sure if there is any 'good' lemon fanfiction involving Naruto and Tinkerbell. Lemon fanfiction often contains inappropriate and not - family - friendly content. It's better to focus on official works or positive fan - made stories that are more in line with the spirit of the original works.
Perhaps in some fanfictions, Naruto is the only one who can see Tinkerbell in the Naruto world. So he has to keep her a secret while also using her help to solve various problems in the Hidden Leaf Village. This idea plays on the idea of Naruto being an outcast at first and now having this unique secret.