Reggie is a Mii from the Switch.
You may get them confused with Reggie (Special)!
Reggie (Switch) originally appeared as the default Mii for the King 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, Reggie 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 Castle00_King00.charinfo.
His Mii name in his Mii data file is おうさまk, which translates to "King k". His height is set to 0. His Mii ID is as follows: 98 9D 7D 8B B0 3A 47 E8 8A 46 E7 EF 1F 33 28 38
His Mii data file does not contain any unused Mii data.
Reggie (Switch)'s role in Miitopia (the King) is described as so:
He seems to bear resemblance to a Mii featured in Miitopia (3DS) promo art, as it seems a handful of the Miitopia Switch default Miis were based around Miis that appeared in promo art for the original game, but it's unconfirmed if Reggie (Switch) and the promo art Mii are meant to be the same character.
The names of the default Miis in Miitopia Switch often vary drastically depending on region. Reggie (Switch)'s name on the Mii Library is going off of the US English version, for consistency. A chart containing all of Reggie's names is located at the bottom of this page.
Reggie (Switch) appears in promo art for Miitopia (Switch) as his in-game role, the King. This image specifically is using a high quality render from a My Nintendo wallpaper reward (Wallpaper B: Miitopia).
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)