Mii QR Codes
Right arrow key to change Mii
For this extra/added twist, press space to start the randomising the Mii's. Now, hold your 3DS where all of the QR Codes can be read. The 3DS will pick a random one to be scanned. To stop randomising, press the down button.
Note: Randomising takes a long time to be recongised by the 3DS so be patient!