Mii on a Tee can hang right next to your Snakes on a Plane shirt in your closet. You've fabricated Miis of yourself, Hitler, your significant other, your neighbor, and Jesus (in that order). Why not display your creations for the world to see?
Pick a color, pick a size, and send off your Mii to creepy leprechauns via Wii-mail or digital photograph, and you've got yourself a bonafide shirt just dripping with fanboy-idity. People will then begin to question your sanity, financial decisions, and why they themselves don't yet have one. Make us proud, guys!