The Nintendo game has also been used to demonstrate the Wii U's Miiverse in-game messaging system.
Players can post messages during gameplay sessions, which can potentially be used to ask for advice or share tips.
Messages posted on the game's map, meanwhile, hint at new suits and abilities.
One user mentions playing as a "flying squirrel" - possibly revealing the inclusion of the Tanooki Suit - and a "baby Yoshi that balloons up to carry you".
The screenshots were posted by NeoGAF and taken from Nintendo's pre-E3 Wii U presentation.
Miiverse also enables users to send messages of pictures and drawings similar to the 3DS Swapnote/Letterbox feature. Messages can also feature a "spoiler" option, to prevent giving game elements away in messages.
Miiverse will be compatible with all Wii U games, and Nintendo has said it will not interrupt gameplay.
Miiverse messaging will eventually also be available as a smartphone app, allowing users to keep up with the Miiverse network from android and iOS devices.
Nintendo has also confirmed the final design for the Wii U controller, and introduced the Wii U Pro Controller.
Nintendo's E3 2012 press conference takes place on Tuesday, June 5 at 5pm BST (11pm EDT).
The E3 Expo will take place in Los Angeles from June 4 to June 7.
> E3 2012: Digital Spy's coverage from the world's biggest gaming expo
Watch a video of the Wii U's E3 2011 reveal below: