If you haven't already done so, I'd recommend watching this to boost some joy today!
I played through all the winter Tracks in Mario Kart 8 DX, and especially adore Merry Mountain! My Mii takes a break as some other miis get included in this compilation and they are...
Cassie (OC) -- Mount Wario
Klara (Pokemon Sword) -- Animal Crossing Winter, VS mode
Mason (@werewolfmonkie) -- GCN Sherbet Land
Avery (Pokemon Shield) -- Ice Ice Outpost
Clara (Wii U CPU) -- GBA Snow Land
Yuki (Hot Shots Golf 1) -- Tour Merry Mountain
I will add more miis as time goes on, as this list is a bit paltry. Enjoy!