Mewtwo is another favorite. Given its complex backstory and powerful abilities, in 'pokemon can talk fanfiction', it can have really profound conversations. It might discuss its feelings of being a created Pokemon, its views on the relationship between Pokemon and humans, and its search for its true place in the world.
I think Mewtwo would be the most fascinating for Naruto to talk to. Mewtwo is a very intelligent and powerful Pokemon. It has complex thoughts about its existence and purpose. Naruto, with his own struggles and growth in the ninja world, could have deep philosophical discussions with Mewtwo. They could exchange ideas about power, identity, and what it means to be different in their respective worlds.
In these fanfics, Pikachu is without a doubt one of the most popular characters. Its popularity in the main Pokemon series carries over here. It can be written as being curious, mischievous, or even a bit scared in different situations. Next, Psyduck is also quite popular. Its confused nature makes for some hilarious reaction - based scenarios. And who can forget about Jigglypuff? When it gets angry because no one is listening to its song in the fanfic, it creates really engaging and funny storylines.
Gary is another character that stands out. He might be the rival who is always one step behind Ash in terms of popularity but is constantly trying to up his game. He could be part of the advanced Pokemon training class and is known for his vast knowledge of different Pokemon species.
Squirtle is very popular. Since it has water - based abilities, it can easily be related to the ink - based battles in Splatoon. It could be a key character in a story where Pokemon and Splatoon characters team up for a water - ink related mission. Also, the main Inkling characters from Splatoon, like Agent 3 or Agent 4, are popular as they are the main representatives of the Splatoon world. They can be shown as having adventures in the Pokemon world, learning about Pokemon training and sharing their ink - fighting techniques with the trainers there.
The player character themselves are often very popular. Since every player can customize their trainer in the game, it gives a lot of room for creativity in fanfiction.
Pikachu is often very popular. Its cute appearance and electric - based abilities can be used in many humorous situations. Also, Team Rocket's Jessie, James and Meowth are popular as they are always getting into comical scrapes while trying to steal Pokemon.
Some original characters created by fanfiction writers can also gain popularity. For example, a young trainer who starts their journey in the Pokemon Red world with a big dream but has to face many difficulties. Their growth and development throughout the story can attract a lot of readers.
Mewtwo is another favorite. Given its psychic powers and origin story of being a genetically created Pokemon, it can be a key figure in battles. It could be fighting for the rights of all Pokemon or be manipulated by the wrong side due to its power.
The mysterious Pokemon Professor in Pokemon Yevatal fanfiction can also be really popular. They are the ones who provide the trainers with their first Pokemon and give them valuable advice throughout their journey. Their knowledge of the Pokemon world is extensive, and they often have a hidden past or some kind of special connection to the rarest Pokemon in the region.
Ash Ketchum is often a very popular character in pokemon multiverse fanfiction. Since he's the main protagonist in the original series, fans like to put him in different multiverse scenarios. Another popular one is Team Rocket's Jessie and James. Their comical antics can be explored in different universes. And of course, many of the legendary Pokémon are popular characters in fanfiction. They often have important roles and are central to many multiverse storylines.