Sanford is a Mii from the Switch.
Sanford originally appeared as the default Mii for Elven Retreat's Fab Fairies Fan 3 role in the files of Miitopia (Switch, Demo), but unused within the demo itself. He later appeared in the full game of Miitopia (Switch). Once the player replaces him with a Mii of their choice, Sanford would never appear again, unless that Mii is deleted. His Mii data file can be found in \cmn\storedata\npc_default_mii.sarc and is named Town02_FanThird.charinfo.
His Mii name in his Mii data file is さんごうk, which translates to "fan three k". His height is set to 40 and his build is set to 31. His Mii ID is as follows: E2 74 5F 8A A8 E9 4B 9E BE 4C A0 B4 89 87 22 CD
His Mii data file does not contain any unused Mii data.
Sanford's role in Miitopia (the Fab Fairies Fan 3) is described as so:
The names of the default Miis in Miitopia Switch often vary drastically depending on region. Sanford's name on the Mii Library is going off of the US English version, for consistency. A chart containing all of Sanford's names is located at the bottom of this page.
Sanford unfortunately does not appear in any promo art. Below is a screenshot of him in-game as his role in Miitopia.
This Mii originally appeared on the Switch!
Here's how to recreate them on the Switch:
Names in other languages
Source: Miitopia (Switch, Demo)