Matt (Wii) originally appeared as one of the 60 CPU Miis to be included with Wii Sports. Since then, he's appeared in Wii Sports, Wii Sports Resort, Wii Party, Wii Music, Wii Fit, Wii Fit Plus, Wii Fit U, Super Smash Bros. for Wii U, and Super Smash Bros. Ultimate. In most of these games (aside from Smash Bros.), his internal ID is 024, however in Wii Music it is 01. His Mii data filename is cpu_mii_024.rcd in Wii Sports, mii_024.rsd in Wii Sports Resort, Wii Fit, and Wii Fit Plus, mii_024.ffsd in Wii Fit U, and is cpu_mii_db01.rsd in Wii Music. Wii Party combines all 100 Mii data files into one larger file named mii_rsd.bin in the same ordering as Wii Sports Resort. His appearances in the Smash Bros. games are limited to prerendered 2D textures and 3D models, as shown below.
As with every CPU Mii, he does not have a creator name or birthday, and has Mingling turned off. His Mii name in his Mii data file is マット. In his Wii U/3DS-format Mii data file, he was originally created on a Wii (1).
His Mii data file contains unused data. His glasses color is set to white (Wii glasses color row 2 column 3) and vertically 2 down. His mole is set to size 4 bigger, and horizontally 3 right.
In Wii Music, his Mii data file is slightly different. While it's mostly the same as it is in Wii Sports Resort, it now includes a filled out Mii ID and console ID. His Mii ID is 80-4f-7d-e1 and his console ID is c2-3d-21-af. His Mii ID tells us he was created on August 30, 2006 at 4:24:36 AM.
According to a September 2020 Nintendo leak about CPU Miis, Matt (Wii)'s nationality is North American.
In the files for Wii Sports, his dominant arm for Baseball (Batting) is left-handed, Baseball (Pitching) is left-handed, and Tennis is left-handed. His unused dominant arm for Boxing is left-handed. His Baseball Pitching style is underhand. He's ranked 55 in Baseball, 0 in Boxing (the best), and 54 in Tennis (the worst out of the Miis that can only appear as opponents). His group IDs are 4, 1, and 0.
In the files for Wii Sports Resort, his Wii country ID is 1, like all CPU Miis. His dominant arm for Table Tennis is left-handed. He's ranked 0 in Swordplay (the best), 70 in Basketball, 48 in Table Tennis, and 73 in Cycling. His unused Canoe and Debug ranks are both 24, matching his ID value of 024.
Matt (Wii) is the best in two sports, and is the only Mii to do so: Boxing in Wii Sports and Swordplay in Wii Sports Resort. Opposingly, Ryan (Wii) is the the worst (in-game) of two sports: Boxing and Swordplay. This is likely more than a coincidence, as something like this happening randomly has a really low chance of occurring. Perhaps there is some sort of connection between the two, but no relationship has been confirmed.
Matt (Wii) is one of the only Miis to share his name with multiple other Miis. While the Mario Kart Wii and WarioWare: Smooth Moves Miis are likely a coincidence, the reason certain CPU Mii names are used multiple times within the Wii series is unknown. He also shares his name with another Mii from the WaraWara Debug. This, however, is most definitely a coincidence.
Matt (Wii) appears in promo art for Wii Music playing the güiro. A younger version of him also appears in the Boxing training gym (more details in this Wii Facts Plus post) found in Wii Sports and the Wii Fit games. Note that here, his favorite color is red, just like in his September 2020 Nintendo leak image icon (which can be found at the top of this page). He also appears as a flat texture in the background and as a 3D model playing Power Cruising on the Wuhu Island stage in the Super Smash Bros. games. For some images, you may have to open them in a new tab to see the whole render.
Names in other languages
Source: Wii Sports Resort