There is a neat trick to do.
If you got 10/10 or 9/10 passes for the lobby, start the Lobby and get the Mii in.
As soon they are in your lobby, close the 3DS and wait for the next 10 Passes.
OPen your 3DS and it will nag you about "new visitors".
Do not greet those 10, or you will throw away...