Definitely Kirby and Pikachu. Pikachu is one of the most iconic Pokémon, known for its electric powers and cute appearance. Kirby, with his ability to copy powers, would have an interesting interaction with Pikachu. He could copy Pikachu's electric power and use it in a unique way. For example, he might use it to power up some machinery in the Pokémon world that has broken down.
Mewtwo would be a great addition. Mewtwo is a powerful and intelligent Pokémon. In a fanfiction, it could be intrigued by Kirby's strange abilities. Mewtwo might initially see Kirby as a threat but then realize they could work together. They could have deep philosophical conversations about their powers and the purpose of their existence while also fighting against common enemies in the combined Kirby - Pokémon world.
Anakin Skywalker as a Pokémon trainer would be really cool. Imagine him with his own team of Pokémon, and how his journey to the dark side might affect them. Also, Yoda could be an interesting character. He might have a small, but very wise Pokémon by his side, like a Bulbasaur that he has trained to be in harmony with the Force.
The Noir Spiderman would be really cool to include. His dark and gritty world view, along with his old - fashioned detective skills combined with his spider - powers, would contrast well with the more modern and upbeat versions of Spiderman. He could offer a different perspective on how to deal with the villains in the Spider - Verse.
One idea could be that Kirby accidentally gets sucked into the Pokémon world through a strange portal. He then teams up with Pikachu to find a way back home while also helping Pokémon in need. For example, Kirby could use his inhaling ability to save some Pokémon from a forest fire by sucking up the flames.
Definitely Darth Vader and Jack O'Neill. Darth Vader with his imposing presence and dark side powers would be a formidable force against the Stargate team. Jack O'Neill, with his military experience and sense of humor, would be a great contrast. Their interactions could be really intense and full of conflict.
Sonic, of course, is a must - have. But also Knuckles from both universes. In Sonic Boom, Knuckles is a bit more of a muscle - brained character in a fun way, while the classic Knuckles is more serious about guarding the Master Emerald. When they meet, there could be some hilarious misunderstandings at first, like Sonic Boom Knuckles trying to show off his strength to the other Knuckles, but then they end up teaming up against a common threat.
Mewtwo could be a very interesting character in this crossover. Mewtwo is a powerful and intelligent Pokémon. In a fanfiction, it could be intrigued by Ben's Omnitrix and the concept of being able to transform into different beings. Mewtwo might initially see Ben as a threat or a potential ally in its own quest for power or understanding of the world. This could lead to some intense and thought - provoking interactions between Mewtwo and Ben.
Anthony Bridgerton would be a great character to include. His strong sense of family and his often stubborn nature could lead to some interesting clashes in a crossover. Say, in a crossover with a fairytale world like Cinderella. He might initially be against the idea of the Bridgerton family getting involved with the magic and 'foolishness' of the fairytale world, but then gradually change his mind.
Bowser and King Dedede teaming up would be really interesting. Bowser's brute strength and his ability to use fire combined with King Dedede's hammer - swinging skills and his own army of minions would pose a great threat to Mario and Kirby. They could be trying to take over both the Mushroom Kingdom and Dream Land for their own greedy purposes, like hoarding all the power - ups and food in both worlds.
I think Kiba and Akamaru would be really fun to include. Kiba's boisterous nature could create some comical moments during the wedding preparations or at the wedding itself. Akamaru could also be part of some cute interactions with Naruto and Fuu. Tsunade would also be an important character. As the Hokage, she could have some say in the marriage, or at least offer her wisdom and support to Naruto. And Rock Lee could be there, showing off his crazy training regime and giving Naruto some motivation for his new married life.
Obviously Ladybug (Marinette) and Cat Noir (Adrien) are must - includes. Their dynamic during a sleepover would be really interesting, like when they're not in superhero mode but still have that connection. Alya would also be great as she's Marinette's best friend and is always eager to be involved in anything Miraculous - related. And Tikki and Plagg, the kwamis, could add a lot of humor. They could be causing little bits of chaos while the humans are trying to have a normal sleepover, like stealing snacks or making strange noises to get attention.