The blue thing looks like the head of a Rex from Super Mario World. The lady Boom Boom appears to be holding a boomerang... maybe she's a new form of the Boomerang Bros.? This looks awesome.
That said, I would like to see a less-linear 3D Mario adventure sometime soon. Don't get me wrong, I love linear 3D Mario. When Mario 64 first came out, I definitely remember wishing for a whole game of "Bowser levels," but I feel like Galaxy 1 and 2 scratched that itch (and to a lesser extent the secret levels in Sunshine). Maybe a new IP should take over for Mario when it comes to non-linear adventures? Or maybe there's one planned for Wii U? It makes sense to have a more streamlined, linear adventure on a handheld. I'm stoked to see a 3D Mario game TRULY embrace the philosophies of 2D Mario.