Official Super Smash Bros Ultimate official blog in Japanese has been recently updated to include the official Mr. Game & Watch, one of the interesting characters that will be available next December 7 when the Nintendo switch will get the title. These details were shared yesterday, but were never offered on a western blog that is still not talking about this character.
It's really weird because all blogs are in all languages they are usually coordinated. However, it seems that this person does not yet have a blog post on the West. It is unknown why this is, and we will be vigilant if it offers more information.
You can see the Japanese entry for this link and the Japanese character ad below: