Matt (Switch) originally appeared as an easter egg to replace the Sportsmate CPU with a Mii CPU in version 1.2.0 of Nintendo Switch Sports. His Mii data file can be found in \Mii\MiiCharInfo001.dat.
His Mii name in his Mii data file is マット ("Matt"). His Mii ID is as follows: 69 D9 04 C2 D0 E5 47 60 8B 15 E4 92 8F A9 21 CE
His Mii data file does not contain any unused Mii data.
While the names of the CPU Miis from Wii Sports Resort were also given to the CPU Sportsmates characters in Nintendo Switch Sports, version 1.2.0 of the game added 10 CPU Miis as an easter egg, activated by holding down L + ZL when on the CPU configuration screen. Matt is one of the CPUs to have gotten a Mii version, however his Mii has been altered since his appearance on the Wii. On the left is a comparison between his Wii appearance and his Switch appearance.
In order for Matt (Switch) to appear in Nintendo Switch Sports v1.2.0, one must begin a game of chambara, and on the CPU configuration screen (where the player selects the difficulty of the CPU), hold down L + ZL on the left Joy-Con controller. If done successfully, a noise will play, and when the player begins the game, the Sportsmate CPU will be replaced with a Mii CPU using this Mii. The Mii CPU has the in-game title "Legend".
Matt (Switch) unfortunately does not appear in any promo art.
On April 13th, 2022, the @NintendoUK, @NintendoEurope, @NintendoFrance, and @NintendoDE Twitter accounts posted this screenshot of Nintendo Switch Sports (not out at the time) featuring what appears to be Matt (Wii) playing against a Sportsmate CPU also named Matt (who has since been redesigned to resemble Matt (Wii) before the official release of the game). However, upon closer inspection, the Matt seen here in this screenshot is actually not accurate to his other appearances in games.
Specifically, his eyebrows type and skin color is set to different options. His eyebrows type is set to Switch option row 2 column 4, and his skin color appears to be Switch option row 2 column 4 as well. The eyebrow type being different also meant the position and size was different, too.
Matt (Switch), while a different design, still resembles both Matt (Wii) and this incorrect Matt in the screenshot.
I have attempted to recreate the Mii shown in the Nintendo Switch Sports photo. Below is my unofficial recreation's Mii Studio code, along with a render to the left. As you can see, from a neutral expression, it can be hard to tell the difference between the eyebrows, making this mistake understandable.
This Mii originally appeared on the Switch!
Here's how to recreate them on the Switch:
Names in other languages
Source: Nintendo Switch Sports (v.1.2.0)