Recently, Nintendo has made a habit of outsourcing or collaborating with other studios on many of its key titles, and it would appear that Wii Fit U is no exception.
Little nugget for Nintendo-watchers... Wii Fit U is made, in part, by Pandora's Tower studio Ganbarion. I spotted that on its title screen.— Stephen Totilo (@stephentotilo) October 4, 2013
It's not known how deeply Ganbarion has been involved with development of the game at this stage. Pandora's Tower director Toru Haga recently praised the Wii U as "unique" and "exciting".
Wii Fit U is released in December, but you'll be able to download and play a one month trial version in November.