Nintendo journalists around the globe are working together to find out what this Medium game is all about. We know for sure that it's coming from Bloober Team. Here are some other details that have cropped up.
If you email the address on the teaser site, you're likely to get this response.
Enjoy your game!
You have only seen half so far.
This is all what I can tell you at this time.
Something big is coming :)
On top of that, here's what an E3 email has to say in its "First Looks from Exhibitors" section.
Completely new model of gameplay. New gender. The game is coming for WiiU or PSvita/PS3 and also for X360, iOS, Android and PC."
So...now we know what's really going on with the game, just not much on what it's about. I'm guessing we'll get more viral marketing during E3! Thanks to Logan and John for the heads up!