Guest C (Hubble) 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 C, except for four: Big Brain Academy: Wii Degree, in which he's called "Student C", Mario Kart 8 and Mario Kart 8 Deluxe, in which he's called "Player", and TV Show King 2, in which he's called "Hubble". This makes TV Show King 2 the only game to give the Guest Miis names! 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 80-00-00-02 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 a1-8c-89-b4 and his console ID is cf-07-81-32 (different from all other default Guest Miis). In his Wii U/3DS-format Mii data file, his Mii ID is the same as his Wii-format Mii data file (extracted from memory), his console ID is zeroed out, 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 C (Hubble) 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 four games call him Guest C. The four exceptions are Big Brain Academy: Wii Degree, in which it calls him Student C, Mario Kart 8 and Mario Kart 8 Deluxe, in which he's called Player, and TV Show King 2, in which it calls him Hubble. TV Show King 2 is the only game to have given the Guest Miis proper names. The other Guest Mii names are Buggy, Bee, Nugget, Mango, and Shigi respectively. This why Guest C's name on the Mii Library website is "Guest C (Hubble)", as while he has been properly named "Hubble" in a game before, most people know him more commonly by simply "Guest C".
Guest C has unique properties in the Japan-only DS game Tomodachi Collection (not to be confused with Tomodachi Life). When creating a new Mii to add as an islander, the Mii the game starts with is Guest C, and gets changed to either the default starter male or female Mii once you choose a gender for the Mii you're about to create. Of course, this is impossible to see in-game, as the Mii does not appear on-screen until you select a gender, but looking into the game's code and RAM confirms it is indeed Guest C.
As shown at the bottom of this page, Guest C is simply the default starter male Mii with a different skin tone.
According to the July 2021 leak, Hubble's race is asian.
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.
Similar to the above example with Wii Party, the back of the Go Play: Lumberjacks box art (shown here with the German version) shows Hubble holding up an axe.
A promotional screenshot for New Super Mario Bros. U gives Guest B, Guest C, and Guest D the names Michael, Thomas, and Catherine respectively. (Note that despite this, they will still use the names Bee, Hubble, and Nugget, as they are the most unique names they've been given - for example, Michael is already the name of a Mii from Wii Sports.)
Mii Studio code
This is Guest C (Hubble)'s Mii Studio code:
You can download Guest C's charinfo-format Mii data file extracted from a save file here.
You can download Guest C's SwitchSDK-format Mii data file extracted from the code of a Switch game here.