At the same conference where Nintendo confirmed Sonic as a playable Smash Bros. character, the company also announced that Mario Kart Wii will include motorcycles when it ships next year. While there's no other information about the new Mario Kart vehicle type, we know that Wario already has his own set of two wheels, as pictured above. It'll be interesting to see which characters can ride on two wheels or if it'll be available to one and all.
Unfortunately, no one is going to find out very soon, as the game has been delayed from early 2008 to Spring 2008. At least Nintendo gave gamers something to look forward to in the way of motorcycles and then reconfirmed that the steering wheel accessory will come with the game.