Story:Eggman has the 7 Chaos Emeralds. He test his new machine and opens up a dimensional portal beween Sonic’s and Mario’s worlds. Eggman travels to Mario’s world and encounters Bowser. Their plans conflict and they fight (Eggman is using one of his machines of course). Eggman defeats Bowser using the Chais Emeralds. However instead of killing him, Eggman strikes a deal with Bowser. He’ll give Bowser the Emeralds and teach him how to use them, and in return Bowser will eliminate Eggman’s enemies so Eggman can take over his own world. Eggman captures Peach and frames Sonic for it while he and Bowser fool Sonic into thinking that Mario is the cause of the dimensional portal and has evil intentions(while aside from their minions, they remain in the shadows). Sonic and Mario characters travel back and forth through the portals to each others' worlds. Due to Eggman and Bowser’s manipulation Mario characters and Sonic characters often fight each other in different encounters. In the end Sonic and Mario end up dueling each other. Meanwhile Donkey Kong finds and fights Bowser, but loses in the end. Knuckles discovers that fight between Mario and Sonic was a trap set up by Bowser and his unkown ally(Eggman). Knuckles fights Bowser and has the upper hand until Bowser uses the Chaos Emeralds to defeat him. After Sonic and Mario finishing fighting a newly transformed Bowser(powered by the Emeralds) arrives and defeats Mario and Sonic who were weakened from fighting each. Just before they are about to be killed by Bowser, Shadow appears and removes his rings to match the Negative Energy of the Chaos Emeralds that Bowser is using. Metal Sonic also appears to finish off Mario and Sonic while Bowser fights Shadow. Even though they are weakened from fighting Bowser and each other, Mario and Sonic still pull off a victory working together against Metal Sonic. Shadow stops Bowser and Sonic retrieves the 7 Chaos Emeralds. Eggman shows up with the Egg Fleet to try to destroy Sonic and his friends, but Sonic turns into Super Sonic and fights off the Egg Fleet. Bowser tries to escape but Super Sonic helps Mario catch up to him and Mario delivers one last blow to Bowser that sends him packing(until the next Mario game that is). Mario and Sonic part as Tails uses the Emerald’s power to close up the dimensional hole and everyone ends up back in their own World.
Gameplay:The game itself would work out like Sonic Adventure 2(Meaning there is Hero and Dark story, excpet with this game it’s Mario and Sonic’s story). It has a Mario storyline in which the events follow Mario and his allies story. Then there is Sonic’s story which fits more to his style of gameplay instead of Mario’s style of gameplay like Mario’s story would, and of course follows the Sonic characters story. then after both sides are completed there is a final story where the Mario and Sonic characters team up to take down Bowser and Eggman/Metal Sonic.
So uh yeah I was bored. >_>
