Among others, Rayman games offer a distinct story-telling experience. They have colorful worlds and exciting quests, similar to the adventures Sonic takes you on. Another option could be Donkey Kong Country, which combines action and story to keep players engaged.
Bowser can also be a great addition. He can be the antagonist who tries to cheat in the Olympics or cause trouble for Sonic and Mario. And from Sonic's side, Knuckles is a fan - favorite. His strength and gliding ability can make for some interesting interactions with the Mario characters. For example, he might get into a friendly competition with Donkey Kong over who is stronger.
One idea could be a team - up between Sonic and Mario to compete in a new, super - difficult event that has never been in the Olympics before. They have to overcome their differences in speed and power - up usage to win.
It adds a new dimension to the Sonic fandom. It gives fans a different way to explore the relationships between characters. For those who love Sonic and Blaze, it satisfies their desire to see them in a romantic context. It also encourages creativity among fans as they write and share these fanfictions.
There could also be some new characters introduced in this fanfiction. Maybe a mysterious figure who has the power to control Dark Sonic or someone who has a connection to the origin of Dark Sonic. These new characters can bring fresh plot twists and new relationships to the story.
A common theme is adventure. Both Sonic X and Sonic Underground are about Sonic and his friends going on exciting adventures, and this is often carried over into the fanfiction. For example, they might be on a quest to find a powerful chaos emerald or save a new world from an evil villain.