Nick is a Mii from the Wii.
Nick 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, and Wii Fit U. In most of these games, his internal ID is 026, however in Wii Music it is 03. His Mii data filename is cpu_mii_026.rcd in Wii Sports, mii_026.rsd in Wii Sports Resort, Wii Fit, and Wii Fit Plus, mii_026.ffsd in Wii Fit U, and is cpu_mii_db03.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.
As with every CPU Mii, he has Mingling turned off. His Mii name in his Mii data file is ニック. In his Wii U/3DS-format Mii data file, he was originally created on a Wii (1).
His Mii data file contains unused data. He does not have any facial hair, yet, his facial hair color is set to be the same color as his hair (Wii facial hair color row 2 column 3).
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-80-80 and his console ID is c2-3d-21-af. His Mii ID tells us he was created on August 30, 2006 at 5:09:20 AM.
According to a September 2020 Nintendo leak about CPU Miis, Nick'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 left-handed. His unused dominant arm for Boxing is right-handed. His Baseball Pitching style is normal. He's ranked 1 in Baseball, 18 in Boxing, and 42 in Tennis. His group IDs are 6, 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 70 in Swordplay, 94 in Basketball, 67 in Table Tennis, and 96 in Cycling. His unused Canoe and Debug ranks are both 26, matching his ID value of 026.
Nick appears in promo art for Wii Music playing the electric guitar and Wii Party playing Match Up. 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 red instead of forest green.
Names in other languages
Source: Wii Sports Resort