Steve is a Mii from the Wii.
Steve 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 041, however in Wii Music it is 26. His Mii data filename is cpu_mii_041.rcd in Wii Sports, mii_041.rsd in Wii Sports Resort, Wii Fit, and Wii Fit Plus, mii_041.ffsd in Wii Fit U, and is cpu_mii_db26.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 スティーブ. 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 80-4e-a2-17 and his console ID is c2-3d-21-af. His Mii ID tells us he was created on August 27, 2006 at 1:53:32 PM.
According to a September 2020 Nintendo leak about CPU Miis, Steve's nationality is English (British).
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 6 in Baseball, 31 in Boxing, and 31 in Tennis. His group IDs are 1, 2, 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 92 in Swordplay, 14 in Basketball, 21 in Table Tennis, and 25 in Cycling. His unused Canoe and Debug ranks are both 41, matching his ID value of 041.
Steve appears in promo art for Wii Music playing the galactic bass. He also appears as a flat texture in the background and as a 3D model playing Frisbee Dog 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