Mike is a Mii from the Wii.
Mike 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 025, however in Wii Music it is 02. His Mii data filename is cpu_mii_025.rcd in Wii Sports, mii_025.rsd in Wii Sports Resort, Wii Fit, and Wii Fit Plus, mii_025.ffsd in Wii Fit U, and is cpu_mii_db02.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 appearance in the Smash Bros. games is limited to a 3D model, 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 マイク. In his Wii U/3DS-format Mii data file, he was originally created on a Wii (1).
His Mii data file does not contain any unused data.
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-7f-c6 and his console ID is c2-3d-21-af. His Mii ID tells us he was created on August 30, 2006 at 4:56:56 AM.
According to a September 2020 Nintendo leak about CPU Miis, Mike's nationality is North American.
In the files for Wii Sports, his dominant arm for Baseball (Batting) is right-handed, Baseball (Pitching) is right-handed, and Tennis is right-handed. His unused dominant arm for Boxing is right-handed. His Baseball Pitching style is normal. He's ranked 45 in Baseball, 16 in Boxing, and 19 in Tennis. His group IDs are 5, 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 right-handed. He's ranked 93 in Swordplay, 76 in Basketball, 16 in Table Tennis, and 45 in Cycling. His unused Canoe and Debug ranks are both 25, matching his ID value of 025.
In Wii Sports Resort Air Sports Island Flyover, he can always be found in the middle of the ocean (east to Wedge Island) in a canoe. There is an iPoint above him called "Extreme Canoeist".
Mike appears in promo art for Wii Music playing the trumpet. He also appears as 3D model using the rocket belt from Pilotwings Resort on the Pilotwings 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.
Note that in his Wii Music render, his tie is sky blue instead of yellow.
Names in other languages
Source: Wii Sports Resort