Thinking harder on it, Bowser Jr. would make most sense. Villain of the mini games, is a bit snarky and reckless. Or it might just be nothing at all and just some impressive animatronic lol.
It'd be real funny if MK gets FJ'ed in an upgrade, ngl.
In all honesty, just glad to see more love given to SNW, and I can't wait to see the end product.