One interesting aspect is the character interactions. For example, when Scooby Doo and his gang cross over with characters from other shows, we get to see how their personalities clash or complement each other. It can be really funny to see the cowardly Scooby interact with a very brave character from another series.
One creative storyline could be that the Winchester brothers get stuck in a town haunted by a ghost. The Scooby Doo gang shows up to solve the mystery. Sam and Dean initially think the gang is just a bunch of amateurs, but they soon realize that the gang's skills in unmasking fake ghosts could be useful in their real - life hunting. Another idea is that a demon has possessed one of the Scooby Doo characters, and the Winchesters have to figure out which one and exorcise the demon without scaring the rest of the gang too much. A third could be that there's a cross - dimensional rift that pulls the two groups together to stop an ancient evil that is using both the Supernatural and Scooby Doo universes as its playground.
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.
Shikamaru and Shaggy would be an odd but fun pair. Shikamaru is lazy but super smart, and Shaggy is always hungry and a bit of a scaredy - cat. They could bond over their love of food (Shikamaru likes his snacks too). And when it comes to getting out of tricky situations, Shikamaru's strategic mind could come in handy for both of them, while Shaggy's ability to run away fast might be something Shikamaru could learn from.
A Scooby Doo and Harry Potter crossover fanfic would be cool. The gang could go to Hogwarts for a school trip and end up having to solve a mystery involving a poltergeist that's scaring students. They'd have to use both their detective skills and some magic knowledge they pick up along the way. Shaggy and Scooby would probably be really excited about all the food in the Great Hall.
A cool concept could be a possession story. A powerful supernatural entity tries to possess members of both groups. Scooby Doo and the Mystery Skulls have to find a way to stop it before it's too late. This would bring out different reactions from the characters. Scooby and Shaggy might be more panicked, while the Mystery Skulls, with their prior experience, would be more strategic in their approach.
Well, perhaps there could be a crossover where Scooby and Shaggy accidentally eat some magic cupcakes in Equestria that give them the ability to talk to the ponies in a special way. Then they discover that there is a mystery surrounding a disappearing magical element in Equestria. The rest of the Mystery Inc. gang shows up to help, and they all join forces with the ponies like Rainbow Dash and Fluttershy to find out what's going on and save the day.
A great plot could be that there's a food - themed mystery. A new, strange food is making people act weird in town. Scooby Doo and Shaggy are, of course, very interested in the food aspect. Tom and Jerry are also drawn to it because it smells so good. Tom wants to keep Jerry away from it, but they all get caught up in finding out where the food is coming from and why it has such an odd effect. The gang uses their detective skills, while Tom and Jerry's constant chasing around the food sources actually uncovers some hidden secrets about the mystery food.
Well, perhaps the Scooby Doo gang could time - travel to the era when Jurassic Park was being built. They start to notice strange things happening, like the dinosaurs seem to be more intelligent than they should be. It turns out that a disgruntled employee is using some kind of new technology to control the dinosaurs and make them cause trouble. The gang has to work together, with Scooby and Shaggy providing some comical relief as they are chased by T - rexes and Velma and Fred solving the mystery.
One idea could be that the Winchester brothers are hunting a ghost in a town where the Mystery Machine gang also happens to be. The Scooby gang initially mistakes the Winchesters for bad guys but then realizes they're all after the same spooky entity. They could team up, with Sam using his research skills and Dean showing the Scooby gang how to handle real weapons (in a non - dangerous way, of course).
Well, one interesting aspect could be the unique character interactions. In Scooby Doo Ghoul School, the regular Scooby gang meets all these spooky female characters. In fanfiction, writers might explore different relationships between them. For example, how the ghouls interact with Scooby and Shaggy in a more comical or even a bit of a mysterious way. It can add new layers to the already fun and spooky world of Scooby Doo.