Though the gameplay is different from that found in the respective franchises, characters from the Sonic and Mario worlds seem to be plentiful and familiar, at least from an aesthetic point of view. Competing characters, which include Bowser, Knuckles, Peach and Dr. Robotnik (or "Eggman," if you prefer), all boast varying ratings according to speed, jumping ability, agility and acceleration. Nintendo's portly plumber naturally sports one of the highest jump levels, whereas the blue hedgehog is tops in speed.
Strangely, none of these statistics seem to have much, if any, effect on the actual gameplay. Human-controlled characters are clearly the only ones that excel, with a 100 meter dash event seeing Bowser winning by a wide margin -- the AI's Sonic comes in dead last. Tailoring characters to be better suited to select events would add some layer of strategy to a thin game (and perhaps it's the case in higher difficulties) but the E3 demonstration implies that performance hinges purely on fine flailing.
As you might expect, the game's controls are akin to many of the Wii's minigame collections and focus on frenzied, repetitive motion. The many "Track & Field-esque" events (dubbed as such by the game's project manager, Ben Harrison) require side-by-side swinging of the nunchuck and wiimote to send you into a gallop, whereas something like the Hammer Toss encourages spirited twirling of the controller. Performing a clapping motion before an event whips the (hideous and two-dimensional) crowd into a supportive rhythm, though it might cause drunken pals to smash your Wii controllers together with unnecessary force.
Since online capabilities aren't expected to extend beyond leader boards, the "drunken pal" element might give Mario & Sonic's 4-player mode (also supported in the DS version) some traction in the long run, but only if you and your inebriated friends know what to expect here: vapid minigames. Try not to be surprised when Mario & Sonic kick off the Olympics this holiday season.