Guest B comes as one of the six default Guest Miis that are included in the Nintendo Face Library. Because of this, he technically appears in every single game with Mii support... that's way too many to count! In nearly every single game, he's called Guest B, except for six: Big Brain Academy: Wii Degree, in which he's called "Student B", Mario Kart 8 and Mario Kart 8 Deluxe, in which he's called "Player", Tetris Party and Tetris Party Deluxe, in which he's called "Tetris2", and TV Show King 2, in which he's called "Bee". Since he's included in the Face Library and not as a file, he doesn't have a filename and consequentially an internal ID.
He has Mingling turned off. His Mii name in his Mii data file is no name, which is the default blank name for Miis.
In his Wii-format Mii data file (extracted from memory), his Mii ID is 80-00-00-01 and his console ID is ec-ff-82-d2 (the same as all default Guest Miis). In his Wii-format Mii data file (July 2021 leak), his Mii ID is 9a-b4-14-e4 and his console ID is b1-de-f7-dd (different from all other default Guest Miis). In his Wii U/3DS-format Mii data file, his Mii ID is 80-00-00-01, and his MAC is EC-FF-82-D2-00-00, very similar to his console ID in his Wii-format Mii data file (extracted from memory).
In his Wii U/3DS-format Mii data file, he was originally created on a 3DS (3).
His Mii data file does not contain any unused data.
As mentioned before, Guest B technically appears in every single game that contains the Nintendo Face Library (AKA, any game that supports Miis), whether you see them or not. Sometimes, they can be tricky to spot, only appearing when the player doesn't have enough or any Miis on their system at all, like in the title sequence for Pilotwings Resort.
Also mentioned earlier was the fact that all but six games call him Guest B. The six exceptions are Big Brain Academy: Wii Degree, in which it calls him Student B, Mario Kart 8 and Mario Kart 8 Deluxe, in which he's called Player, Tetris Party and Tetris Party Deluxe, in which he's called "Tetris2", and TV Show King 2, in which it calls him Bee. TV Show King 2 is the only game to have given the Guest Miis proper names. The other Guest Mii names are Buggy, Hubble, Nugget, Mango, and Shigi respectively. The name "Bee" given to him by TV Show King 2 is a reference to the fact his original Guest letter is B. As for the other Guest Miis, their names do not seem to come from anything.
According to the July 2021 leak, Guest B's race is caucasian.
Note: Many images on this page have been cropped. While this was done for formatting reasons (to reduce the vertical space being taken up by unimportant parts of the image), you can still open the image in a new tab to view the full uncropped image.
According to Nintendo's Mii Usage Guidelines appendix A.1, the default Guest Miis are not allowed to appear in advertising.
Guest B also appears in another Wii Fit screenshot by himself in the bottom right corner.
Mii Studio code
This is Guest B's Mii Studio code:
You can download Guest B's charinfo-format Mii data file extracted from a save file here.
You can download Guest B's SwitchSDK-format Mii data file extracted from the code of a Switch game here.