I think Pikachu would be really interesting. It's so cute and energetic. In the fanfiction, it could use its electric powers to light up spooky places that Scooby Doo and the gang are exploring. Also, its reactions to all the strange things in Scooby Doo's world would be hilarious.
Scooby Doo himself would be a very interesting character in this cross - over. He is known for being cowardly but also having a big heart. When he meets the Pokemon, his fear of the unknown could lead to some really funny moments. And his love for food might even be related to some of the Pokemon's food - like berries. He could also use his sense of smell to help find hidden Pokemon or clues in the mystery.
Misty from Pokemon could be quite interesting. She's strong - willed and has a temper. In the 'pokemon meets scooby doo' scenario, she could get frustrated with Scooby's antics but also be impressed by his loyalty to his friends. Her water - type Pokemon could be useful in dealing with any fire - based threats or mysteries involving water, and she could add a different dynamic to the group with her no - nonsense attitude.
Shaggy and Amethyst could be a great combination. Shaggy is always a bit of a scaredy - cat but also has a big heart. Amethyst is laid - back and loves to have fun. They could bond over their love for food and their easy - going attitudes, while also helping each other out during the adventures. Shaggy might be hesitant at first when facing gem - related dangers, but Amethyst could encourage him and show him that there's nothing to be too afraid of.
Naruto and Shaggy could be an interesting pairing. Naruto's high - energy and brave nature could contrast with Shaggy's cowardly but kind - hearted personality. They could learn from each other. Naruto could teach Shaggy to be more courageous, and Shaggy could introduce Naruto to some delicious human world food.
Naruto and Scooby would be a really interesting pairing. Naruto's energy and enthusiasm would contrast with Scooby's cowardice. Naruto could encourage Scooby to be brave and Scooby could teach Naruto about having fun even in scary situations. Also, Naruto's ability to make shadow clones could be used in really creative ways to help solve mysteries, like sending clones to different areas while Scooby and the gang follow the main clue.
In this fanfiction, it could start with Scooby Doo and Shaggy being chased by a 'monster' which turns out to be a large, misunderstood Pokemon. The Pokemon trainers then come in to help calm the Pokemon. As they get to know each other, they find out that there is a mystery surrounding a series of disappearances in the area. The combined skills of the Pokemon's powers and the Scooby gang's sleuthing lead them to a hidden lair where a mad scientist is trying to use Pokemon DNA to create an army of super - monsters. They must work together to stop this evil plan.
Vivi and Velma would make an interesting pairing. Vivi has her own knowledge of the supernatural world, and Velma is the brains of the Scooby Doo gang. They could share their insights and research methods, and Vivi might introduce Velma to some new concepts in the supernatural realm that Velma has never considered before.
Fred and Erza would make an interesting pairing. Fred is used to being the leader in solving mysteries, and Erza is a strong and fearless leader in Fairy Tail. They could combine their leadership skills to lead the group in solving a complex mystery or fighting a powerful enemy.
Naruto and Shaggy would be really interesting. Naruto is all about courage and facing challenges head - on, while Shaggy is often timid and scared. Their interaction could be really funny and also lead to some character growth for Shaggy as he might learn to be braver from Naruto. Also, Sasuke and Velma could have an interesting dynamic. Sasuke's brooding and intelligent nature could pair well with Velma's analytical skills as they try to solve the mysteries together.
Ash from Pokemon and Shaggy from Scooby Doo are also commonly paired. Both are a bit naive in their own ways and are always ready for an adventure. They could share their experiences of traveling and facing challenges, whether it's in the Pokemon world or solving a Scooby Doo mystery.
Cas (Castiel) and Shaggy would be an interesting combination. Cas is an angel who doesn't always understand human behavior, and Shaggy is this skittish but kind - hearted character. Cas might be confused by Shaggy's fear of everything, but also find his simple kindness endearing. Shaggy, on the other hand, might be initially terrified of Cas but then realize he's a friend. It could lead to some really cute and comical interactions in the fanfiction.
I think Sonic himself would be the most interesting. He's so different from the Pokemon world. His super speed and his attitude would really stand out. He doesn't have the typical powers of a Pokemon, like shooting fire or electricity. His way of dealing with problems, which is mostly running really fast and spinning into things, would be really unique in the Pokemon world.