You saw the logo unceremoniously flashed on the screen at Nintendo's E3 presentation; now see the trailer and screens. The Miis have cleaned up after their tame soiree, handing the keys to the venue back to Mario and pals, who are throwing Mario Party 9 on the Wii.
We were going to joke about Mario being a serial partier, but we realized that just twelve get-togethers (counting the GBA, DS, and e-Reader outings) since 1998 is actually not that much social interaction.