To get the special games you must get all three Specter Coins behind any of the three panels in Academy mode but you must win that panel to get the coins and you must graduate.
Unlockable
How to Unlock
Chef Chimpy
Graduate Jr.3 and win the panels that has the specter coins behind it
Every Monkey's Golf
Graduate Sr.1 and win the panels that has the specter coins behind it
Gran Tourismonkey
Graduate Jr.2 and win the panels that has the specter coins behind it
Monkey Dice
Graduate Jr.1 and win the panels that has the specter coins behind it.
