Towards the end of GDC, Nintendo's Shigeru Miyamoto revealed they had been toying with the concept of Mii creation for almost 20 years but were "never able to turn it into much of anything". It finally found a home on the Wii, but a recent developer's chat uncovered a few early screenshots of the Mii editor -- on the DS.
The concept doesn't seem to have changed much from this build to the final product, though the visuals did go through a much-needed evolution. Having a portable version of our Mii does have a certain charm, but it isn't likely Nintendo will invest resources in a pocket-sized Mii creator.