At the world map, hold Select and press Up, Right, Down, Left. If you entered the code correctly, a small "Big Secret" location will appear. Go there, and select "Capture Invizimals". There are four special Invizimals that require special images to be attracted.
BoneshellWin ten online fights in Infrastructure mode to unlock Boneshell.
MobyWin ten online fights in Ad Hoc mode to unlock Moby.