Guest D (Nugget) comes as one of the six default Guest Miis that are included in the Nintendo Face Library. Because of this, she technically appears in every single game with Mii support... that's way too many to count! In nearly every single game, she's called Guest D, except for four: Big Brain Academy: Wii Degree, in which she's called "Student D", Mario Kart 8 and Mario Kart 8 Deluxe, in which she's called "Player", and TV Show King 2, in which she's called "Nugget". This makes TV Show King 2 the only game to give the Guest Miis names! Since she's included in the Face Library and not as a file, she doesn't have a filename and consequentially an internal ID.
She has Mingling turned off. Her Mii name in her Mii data file is no name, which is the default blank name for Miis.
In her Wii-format Mii data file (extracted from memory), her Mii ID is 80-00-00-03 and her console ID is ec-ff-82-d2 (the same as all default Guest Miis). In her Wii-format Mii data file (July 2021 leak), her Mii ID is df-b7-14-66 and her console ID is f9-74-da-f8 (different from all other default Guest Miis). In her Wii U/3DS-format Mii data file, her Mii ID is the same as her Wii-format Mii data file (extracted from memory), her console ID is zeroed out, and her MAC is EC-FF-82-D2-00-00, very similar to her console ID in her Wii-format Mii data file (extracted from memory).
In her Wii U/3DS-format Mii data file, she was originally created on a 3DS (3).
Her Mii data file does not contain any unused data.
As mentioned before, Guest D (Nugget) 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 her Guest D. The four exceptions are Big Brain Academy: Wii Degree, in which it calls her Student D, Mario Kart 8 and Mario Kart 8 Deluxe, in which she's called Player, and TV Show King 2, in which it calls her Nugget. TV Show King 2 is the only game to have given the Guest Miis proper names. The other Guest Mii names are Buggy, Bee, Hubble, Mango, and Shigi respectively. This why Guest D's name on the Mii Library website is "Guest D (Nugget)", as while she has been properly named "Nugget" in a game before, most people know her more commonly by simply "Guest D".
According to the July 2021 leak, Nugget's race is black.
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.
However, as shown in this Wii Facts Plus post, Nintendo has broken this rule before, so it's possible a Wii-era game might've released some while these rules were much more relaxed.
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 D (Nugget)'s Mii Studio code:
You can download Guest D's charinfo-format Mii data file extracted from a save file here.
You can download Guest D's SwitchSDK-format Mii data file extracted from the code of a Switch game here.