From title screen .
Go to Wi-Fi (Line 4).
Go to "Gift Mode" (Line 2)
Go to "Gift" (Line 3)
This will allow you to battle rare or unobtainable monsters. If you defeat them, you earn them.
hope this helps out.
*Edit* oh and i forgot to mention, this is for the Pro version
Edited by Lightning Edge, 17 June 2011 - 12:02 PM.