There are also Special Miis, which wear gold pants. These Miis are currently only out in Japan, dubbed Celebrity Miis, and it is reported that these will be sent to the MiiPlaza of players via WiiConnect24. These Miis can't be edited or copied. If you transfer a Special Mii to a Wii or to a Wiimote, it'll be removed from their original location, instead of traditionally making a copy of them.
Blogger David Hawley has apparently uncovered, using a hex editor, the future of Nintendo avatar pants: "Special Miis" with pants of gold. If you can get your Mii over to your PC, then you can edit it in hexadecimal to create such a Special Mii. Special Miis cannot be copied, only moved; if you try to put two identical Special Miis in a Plaza, they will disappear.
He has also figured out how to make "foreign" Miis, who are adorned with the blue pants worn by Miis made in other people's Wiis and visiting your Plaza.
Check out the tutorial at...Creating Special Mii's by David Hawley