Most people have seen one or more of the Nintendo Switch / Reggie / Miyamoto videos from The Tonight Show Starring Jimmy Fallon. The live debut of the system was a highlight, as was the sight of Miyamoto-san and Bill Trinen in the audience.
The whole thing was a bit of a GIF gift, too:
Some attention has also been on Shigeru Miyamoto's awesome t-shirt, which has a 'Samurai Mario' and a handsome design.
It's easy to be dismissive of any excitability about it, but then Bill Trinen went and tweeted with a nudge and wink; he knew exactly what he was doing.
Some believe it points to a theme in the 3D Mario game coming to Switch, some wonder whether it references a Dynasty Warriors / Mario tie-in along the lines of Hyrule Warriors. Others think it's just a rad shirt commemorating an aspect of Japanese culture. Polygon also reports that Miyamoto-san wore it again at another press event, but that might just mean he forgot to pack an extra shirt.
It seems it could also be an elaborate pun related to Super Mario Run, which would make sense as the app was the main reason for Miyamoto-san's visit to the US.
There are a lot of theories bouncing around, but it's worth not cynically disregarding it all. For example, a piece of art for The Last of Us evidently teased the upcoming 'Part Two' back in September, and no-one knew it at the time.
What does Miyamoto-san's Mario t-shirt mean? Go wild with your theories in the comments.