It's fake y'all!
Update: A couple of red flags have been pointed out since the video first made the rounds. First, the YouTube icon pictured isn’t the latest logo. Secondly, while Mario Kart 8 Deluxe seems to be shown on the console as a digital download, that would take up 6.8GB of memory – yet it only shows that 2GB is used in the video. For now we unfortunately have to lean much closer to this being fake.