This is about the series on Nintendo Kai. For the series at the Olympic Games, see here.
Super Mario Bros. and Sonic the Hedgehog is a series with SEGA and Nintendo developing the game and publishing the game on Nintendo's Nintendo Kai. Most of the games have been published on the Nintendo Kai, but it then the saga continues on the Nintendo 4DS.
Mario and Sonic have to team up in order to stop King Bowser Koopa and Dr. Ivo "Eggman" Robotnik to release their ultimate creation, The Mecha EggBowser 3.0 to take over all the dimensions to have each villian a planet of their own.