Check out this image of Mario Bros for Wii U
One user points out that “being a flying squirrel is way more fun” than it should be. This indicates that Mario will have a power-up that turns him into a flying squirrel-plumber hybrid.
Another user in the picture references a baby Yoshi. I love how Nintendo likes to let little details like this slip out.
Also the middle comment seems to indicate that there will be achievements of some sort with the gold notification that the user cleared that stage within a certain time frame.
This game is looking more and more like it may end up being called Super Mario Bros 4.