One interesting plot idea is Sonic being mistaken for a new superhero by the Avengers. He has to prove himself and his abilities to them. Another is when the Avengers' world is invaded by Sonic's enemies, and they have to work together to defeat them.
One interesting plot is the exchange of combat techniques. The Power Rangers could teach the Avengers their martial arts - based fighting styles, while the Avengers could show the Rangers how to use their high - tech gadgets more effectively in combat.
A plot idea could be that an evil scientist has created a device that combines the powers of both Sonic's chaos emeralds and Spider - Man's radioactive spider - bite. This new power source is unstable and threatens to destroy both their universes. Sonic and Spider - Man must work together to stop the device. It's interesting because it forces them to understand each other's powers and find a way to neutralize this new threat.
One plot idea could be Dark Sonic having to face a new villain that is even more powerful and is threatening to destroy his world. He has to find a way to control his dark powers even more to defeat this foe.
A possible plot for 'sonic meets sonic boom fanfiction' is that a strange rift in the dimensions brings Sonic and his friends from the classic Sonic world into the Sonic Boom world right when they are about to have a big celebration. However, the Sonic Boom characters are initially suspicious of these new arrivals. But as they start to realize that a common enemy is behind the rift, they join forces. Sonic and Sonic Boom Sonic could have a friendly competition to see who can defeat the most badniks during the adventure, which also helps them bond and understand each other's strengths better.
One idea could be Sonic discovers a magical land where all the characters are in an abdl state. He has to navigate this new world while also dealing with his own changed circumstances. For example, he might have to learn to control his new abilities that come with this state.
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.
A really cool plot idea could be that the Avengers are watching Endgame in a sort of 'alternate reality cinema' where the events in the movie start to bleed into their real world. So they have to stop the movie from fully playing out to prevent chaos in their own universe. This would involve a lot of action and strategic thinking as they try to stop things like Thanos from emerging from the screen while also trying to understand the significance of what they're seeing in the movie.
One idea could be that the mutants and the Avengers have to team up against a common enemy that is immune to their individual powers. So they must learn to combine their abilities in new ways. For example, Wolverine's healing factor could be used to keep an injured Avenger alive during a long battle while Iron Man figures out a way to defeat the enemy.
One idea could be that Harry Potter is magically transported to the Avengers' universe. He could use his magic to help the Avengers in battles, like creating protective shields with spells. Another idea is that the Avengers are somehow sent to Hogwarts, and they have to learn about magic while also dealing with threats in the wizarding world. For example, Iron Man might try to figure out how to integrate his technology with magic.