One idea could be that the Upside Down in Stranger Things is somehow connected to a dark and distorted Pokemon world. The Demogorgon could be like a super - powerful and corrupted Pokemon. The kids from Stranger Things would have to team up with their favorite Pokemon to fight against the forces of the Upside Down.
Perhaps Eleven has a special ability to communicate with Psychic - type Pokemon. In the story, a new Pokemon arrives in Hawkins that is causing chaos, and it's up to Eleven and her friends, along with their Pokemon pals, to figure out what's wrong with it and stop it from destroying the town. They might discover that the new Pokemon is being controlled by the Mind Flayer.
Another possibility is that Pokemon exist in the Naruto world. Some ninja could have Pokemon as partners instead of traditional ninja animals. For example, Sasuke could have a Dark - type Pokemon like Umbreon that would match his cool and mysterious personality. And the Pokemon battles could be incorporated into the ninja battles, adding a new layer of strategy.
Maybe a Pokemon Champion from the Pokemon world gets transported to the Naruto universe. This Champion could start training ninjas in the ways of Pokemon battling. They could introduce Pokemon-like creatures that exist in the Naruto world in a new way, like using chakra to power up these 'Pokemon' equivalents.
One idea could be Sonic getting transported to the Pokemon XY world. He could use his speed to help trainers catch fast - moving Pokemon. For example, he could outrun a Pikachu and lead it towards a trainer's Pokeball.
One idea could be a story where Naruto is somehow transported to the Pokemon Ranger world. He might use his ninja skills to help the Pokemon Rangers in their quests. For example, his speed and agility could be useful in chasing down poachers or rescuing lost Pokemon.
A possible fanfiction could involve a powerful maelstrom created by a villain who wants to merge the Naruto and Pokemon universes for their own evil purposes. The Pokemon trainers and Naruto ninja would have to team up to stop this. For example, Pikachu's electric attacks could be combined with Naruto's Rasengan to create a super - powerful attack against the villain.
One idea could be that Naruto somehow gets transported to the Pokemon world. There, he meets a Rayquaza that has a special connection to his chakra. They team up to face a new threat that is endangering both the Pokemon world and Naruto's world. Naruto could use his ninja skills, and with the power of Rayquaza, they could create unique battle strategies.
One way to blend them is through the concept of friendship. In Stranger Things, the friends' bond is very strong. In Pokemon, the trainer - Pokemon relationship is also crucial. So, you could write a story where the Stranger Things gang forms a special bond with their Pokemon. They rely on each other in battles against the combined threats of the Stranger Things monsters and the bad guys in the Pokemon world. The Pokemon could also help the characters deal with their personal issues, like how a certain Pokemon's calm nature helps Will overcome his post - Upside - Down trauma.
One idea could be a story where Naruto is transported to the Pokemon X and Y world. He could use his ninja skills to catch Pokemon in unique ways. For example, he might use his shadow clone jutsu to surround a wild Pokemon and then throw a Poke Ball with perfect accuracy.
Perhaps in a fanfiction, Hopper is hurt while protecting Eleven. The government agents are after her again, and Hopper steps in between them. They use some sort of experimental weapon on him that causes him internal injuries. Eleven then has to use her powers to keep him alive while they try to find a way to heal him. This could lead to a lot of emotional moments between them as Eleven blames herself for Hopper getting hurt.
One idea could be a crossover where the ninjas from Naruto enter the Upside Down in Stranger Things. They use their jutsu to fight the strange creatures there. Another could be characters from Stranger Things learning chakra control in the Naruto universe. Maybe Eleven could use her powers in combination with Naruto's Rasengan.