In a Sonic X over fanfic, one could write about Sonic getting trapped in a virtual reality world created by Dr. Eggman. In this world, Sonic has to overcome not only the digital obstacles but also his own doubts and fears. Another idea is a fanfic that explores what would happen if Sonic X's characters had to deal with a natural disaster on their planet. And yet another could be a story that focuses on the backstory of one of the minor characters in Sonic X, like how Cream the Rabbit came to be friends with Cheese the Chao.
One idea could be a fanfic where Sonic and his friends get transported to an alternate dimension filled with new and strange enemies. Another could be a story focusing on the relationships between the characters in Sonic X, like a deeper exploration of Tails' admiration for Sonic. And a third idea might be a time - travel fanfic in Sonic X's universe, where Sonic has to go back in time to prevent a great disaster.
One idea could be a crossover universe where Lancelot, from the Arthurian legend, is somehow transported to Sonic's world. Maybe he teams up with Sonic to fight against a common enemy that is threatening both their realms. For example, an evil wizard from Lancelot's world has joined forces with Dr. Eggman, and they have to use their combined skills to stop them.
One idea could be a Sonic fanfic where Sonic and his friends travel to a parallel universe where the roles are reversed. For example, Eggman is the hero and Sonic is the villain. It would be really cool to see how they handle this new situation.
One idea could be a racing tournament where Mario and Sonic team up against some new, powerful villains. They have to combine their unique skills, like Mario's jumping and Sonic's speed, to overcome the challenges of the track which is filled with traps from both of their worlds.
A Sonic OC fanfic could center around an OC who is a healer. In a world full of battles against Dr. Eggman, this OC would use their healing powers to patch up Sonic and the gang after tough fights. They could also have a backstory about how they learned their healing abilities, maybe from an ancient and forgotten tribe in the Sonic world. This would add depth to the character and the fanfic as a whole.
One idea could be that Sonic and Inspector Gadget team up to stop Dr. Robotnik and Dr. Claw who have joined forces. Sonic's speed and Gadget's gadgets would make for an exciting combination. For example, Sonic could use his speed to lead the bad guys into Gadget's elaborate traps.
One idea could be a race between Naruto and Sonic through different dimensions. Naruto could use his shadow clones to create distractions while Sonic zooms past. Another idea is a team - up to fight a common enemy that has the ability to disrupt both their worlds, like a villain who can steal chakra and chaos emeralds. Maybe Sonic could teach Naruto some of his super - speed techniques in exchange for learning some ninja skills.
One idea could be a crossover adventure where Sonic and Samus team up to stop a powerful, universe - threatening villain. They could combine their unique abilities, like Sonic's speed and Samus' combat skills and advanced weaponry.
One idea could be that Sonic and Kirby team up to save their respective worlds from a common enemy. Maybe a powerful dark force is threatening both Mobius and Pop Star. They could combine their unique abilities, like Sonic's speed and Kirby's inhaling and copying powers to defeat the foe.
In some fanfictions, they might explore the differences in their personalities. For example, Classic Sonic's more simplistic and straightforward approach contrasted with Modern Sonic's more complex and sometimes cocky attitude. They could start off not getting along due to these differences but then learn to work together. Maybe there's a story where they are both trapped in a strange dimension and have to rely on each other's skills. Classic Sonic's spin - dash and ability to handle more 2D - like terrains, while Modern Sonic can use his homing attack and boost in the more complex 3D areas of the dimension.
One idea could be that Sonic from Sonic X accidentally travels to the Sonic Boom universe and has to adapt to the different environment and new versions of his friends. Maybe he teams up with Sonic Boom Sonic to defeat a common enemy that has found a way to cross between the two universes.