As another Mystery Mushroom form, of course. Here’s a trailer showing him being unlocked in the new event course:
You will be able to play this course and unlock this costume on March 31st 2016. Or tomorrow, for anyone who hasn’t checked a calender for a while.
So what can I say? Well, not much, it’s a decent new costume based on an underrated series of platformers. What’s more, the Starfy series has already made cameos in the Mario franchise, with Starfy himself appearing as an enemy in Super Princess Peach:
And on a poster in Mario & Luigi Superstar Saga:
So yeah. Starfy is now making his third appearance in the Mario franchise. Cool eh?