According to an old MTV interview, Shigeru Miyamoto revealed that when Nintendo completed the development of Twilight Princess, the team decided to kick back and have some fun by placing Miis all over Hyrule.
Apparently, this isn’t out of the ordinary for the development team. Miyamoto explained:
“This is something our development teams do all the time once they get done with a game and start thinking about other ideas.”
It could have been interesting to see this happen in the final version of the game, perhaps via an optional, unlockable mode where existing citizens of Hyrule were turned into Miis. All I know is, somehow the idea of working at Nintendo just got even more magical.