Remember that Mario game Nintendo said they were going to announce at E3? Well Miyamoto and company made good on their promise, announcing New Super Mario Bros. U at their E3 press conference a short time ago.
As you might expect, based on the name, New Super Mario Bros U takes a lot of cues from it's "new super mario" predecessors in terms of aesthetics and gameplay. Four player co-op returns, but with a twist. A fifth player can use the Wii U gamepad to help the other four players using the touchscreen.
Where it distinguishes itself, based on Nintendo's presentation, is the ability to integrate the experience with all of your Wii U-playing friends. When you get a new high score, perform a speed run or make a comment about a level in Miiverse (the Wii U's social hub) the information will show on your friend's world map. The goal being to recapture the magic of experiencing Mario socially, without actually playing in the same room.