The different musical themes of the Wii and its applications, such as the Mii Channel and Wii Shop Channel, were written by Nintendo's in-house Music Producer Kazumi Totaka, who is responsible for numerous game themes and scores to some of Nintendo's most celebrated IPs and who is also responsible for the reccurring "Totaka's Song" Easter Eggs hidden in the numerous games he's worked on.
Contributed by PirateGoofy