One idea could be that Mario and Sonic have to team up to save both their worlds from a new, powerful villain that is threatening to merge their dimensions in a chaotic way. For example, Bowser and Dr. Eggman could accidentally awaken an ancient evil while arguing over who is the better baddie.
Well, a cool plot for Mario Sonic crossover fanfiction might involve a new character that can travel between their worlds freely and is causing chaos. Mario and Sonic initially suspect each other but then realize they need to join forces. For example, this character could be stealing power - ups from Mario's world and Chaos Emeralds from Sonic's world to gain ultimate power. They would have to explore both worlds, facing their respective villains' minions along the way.
One idea could be a racing tournament where Mario, Sonic and their friends compete. It would be a high - speed adventure with crazy power - ups from both universes. Maybe Mario could use a Sonic - inspired speed boost item, and Sonic could try out a mushroom to grow big for a short time.
One idea could be that Sonic and Mario have to team up to save both their worlds from a new, powerful villain who has the ability to manipulate time. This would force them to use their unique speed and jumping abilities in new and creative ways.
One idea could be a friendly rivalry between Mario and Sonic that gets intense during the Olympic Games. Maybe they both want to prove who is the better athlete in a new and unique event.
One idea could be that Mario and Sonic team up to compete in a new, never - before - seen Olympic event. They have to overcome their differences in style and learn from each other to win.
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.
One idea could be that Mario and Luigi get transported to a strange new world where the rules of their own world are all mixed up. They have to use their combined skills in a whole new way to find their way back home. For example, Luigi might have to be more brave and take the lead in some situations while Mario has to use his speed in different ways than he's used to.
One plot idea could be a race across different dimensions. Sonic, with his speed, Mario, with his jumping skills, and Yoshi, with his unique abilities, could be competing to find a powerful artifact lost in these dimensions. Another could be a team - up to stop an evil force that threatens both their worlds. The evil force might be trying to steal the chaos emeralds from Sonic's world and the power - ups from Mario's world. And a third idea is a friendship - building adventure where they have to help Yoshi find his long - lost family in a strange new land that combines elements of both Sonic and Mario's universes.
Maybe there's a strange energy rift that pulls Sonic into Megaman's world and vice versa. Sonic's speed causes chaos in Megaman's more structured world, while Megaman's weapon - based combat puzzles Sonic at first. However, they soon find out that there are common enemies that are trying to take advantage of the rift to gain power in both worlds. So they combine their abilities, like Sonic using his speed to help Megaman reach difficult areas, and Megaman using his blasters to clear paths for Sonic.
A cool plot might be that there's a strange energy surge that starts to merge their two worlds together. Sonic and Mega Man meet and initially misunderstand each other's motives. But as they figure out the cause of the energy surge, they realize they need to work together. Sonic's speed can help Mega Man reach places quickly, and Mega Man's weaponry can assist Sonic in combat against tougher enemies.