Mario and Sonic: Worlds Collide is a Fan Game created by the two companies C.I.A. Station, Inc. and Red Inc. that is made especially for the Wii. This game will release shortly after Mario and Sonic at the Winter Olympic Games has been released. Mario and Sonic: Worlds Collide features more playable characters than Mario and Sonic does, and each character yields a weapon specific to it.
Sonic the Hedgehog series
Bowser and Dr. Eggman decide to join forces and secretly plan to attack both their enemies' homes. They first decide to attack Sonic's home and then attack Mario's home and hopefully be able to capture Peach. Bowser and Eggman put their plan to action and attack Sonic's home. When Dr. Eggman shoots the first cannonball (which thankfully misses Sonic's house) Sonic wakes up from one of his naps and goes to see what is happening. When he sees Dr. Eggman telling Bowser (Sonic doesn't know who Bowser is yet) where to shoot the bombs, Sonic uses his speed to create a sonic boom to power down Eggman's cannonball-shooting machine. Soon after, Bowser and Dr. Eggman fly away in Bowser's Koopa Clown Car to the Mushroom Kingdom. Suddenly, Amy, Tails, Knuckles, Blaze, Big, Vector, and even Silver and Shadow appear and offer to help Sonic stop Dr. Eggman and the spiky turtle guy (WHAT? They don't know who Bowser is yet!), and Sonic accepts.
When the two villains arrive at the Mushroom Kingdom, they begin to attack Peach's castle. Mario and Luigi hear the explosions of the cannonballs and go to see what's going on. There, the two heroes find the castle in ruins, but find Peach and Daisy safe from harm. (Why is Daisy there, you ask? Beats me...) Peach and Daisy tell Mario and Luigi that Bowser and someone else were attacking the castle. Suddenly, Yoshi, Birdo, Wario, and Waluigi arrive. Peach asks the four to help. They accept. Then, a beam of light appears and touches the ground. Sonic and his team emerge and ask if Mario's team will help them stop Bowser and Dr. Eggman, and Mario's team says yes.