Perhaps in the fanfiction, Naruto's past catches up when he discovers that he has a long - lost relative who has a unique power. This relative might be on a different path, either good or bad, and Naruto has to figure out how to deal with this newfound family connection. It could involve a lot of emotional turmoil as he tries to understand his place in this new family dynamic.
In some versions of this fanfiction, Naruto's past could catch up in terms of his training. For example, he might find out that there were some hidden techniques or knowledge that he was supposed to inherit from an old master. This discovery could lead to him rapidly increasing his power and facing new challenges as he tries to master these forgotten skills.
One interesting plot could be Naruto using his future knowledge to prevent some tragic events in the past. For example, he might stop the death of certain characters or change the course of a big battle.
One interesting plot could be Naruto using his future knowledge to prevent the Uchiha massacre. He might try to change Itachi's situation and find a way to resolve the conflict between the Uchiha clan and the village without all that bloodshed.
A plot where the past and future ninja teams have to compete in a tournament. Each team has their own set of skills and strategies based on their time periods. The past teams might rely more on brute force and basic jutsu, while the future teams have more advanced and unique jutsu. It would be a great opportunity to see the evolution of ninja techniques and how the different generations interact.
The Akatsuki members might also play a role. Since Naruto's past could be related to the larger shinobi world, the Akatsuki, with their various motives and powers, could be involved. For example, if Naruto's family had something to do with a powerful tailed beast that the Akatsuki is after, it would draw them into the story and make them important characters in this fanfiction.
Maybe Snape catches them in the middle of a magical experiment gone wrong. Harry and Ginny were trying to recreate an old spell they found in a dusty book, and the resulting chaos draws Snape's attention. He then has to decide whether to punish them or help them fix the mess.
One interesting plot could be that Ash catches a shiny Pikachu which has some unique powers, like being able to communicate telepathically with other Pokemon. This would change the way Ash interacts with his team and the challenges he faces in battles.
One interesting plot could be Naruto using his future knowledge to prevent some of the tragedies that happened in the original story. For example, he might be able to stop the Uchiha massacre. Another plot could be him training his younger self, leading to a much stronger Naruto earlier on. And perhaps he could also change the relationship between the different ninja villages, promoting more peace and cooperation from an earlier stage.
One interesting plot could be Naruto using his future knowledge to prevent the death of some important characters like Jiraiya. He might be able to warn Jiraiya about Pain's true identity in advance and change the outcome. Another plot could be Naruto influencing the relationship between Sasuke and the village earlier, preventing Sasuke from leaving in the first place. He could also use his experience to train more effectively from a young age and become even stronger faster.
Well, one possible interesting plot could be Ash using his unique bond with his Pokémon to outwit Mewtwo. Maybe he convinces Mewtwo that not all humans are bad through the kindness shown by his Pokémon team.
One possible plot could be that Ash discovers Frilish in a mysterious new region and has to overcome various obstacles like other Pokémon trainers or difficult terrains to catch it.