Check Mii Out Channel Cheats :
Secret - How to make someone's miis more poplular!
When you see a mii and click on it, you see the word favorite. Click on it and you probably know that it makes the mii one of your favorites, but it also raises the mii's popularity so if you want to make a mii popular, make it your favorite. It doesn't work on the miis you create though. You need to use a different wii and make it a favorite there.