Go to the Palace Of Prostheses, use the filing system, and enter "Monkey-Pumpkin-Bunny" as a code to get the Ryan J. Danzwithwolves file. Look at the file, pause the game, then select the "Bonus Stuff" option to access Murrayball. Note: This must be done before looking for the No-Nosed Man.
Successfully complete all Monkey Kombat moves in the moves table (press R2) for each Monkey Stance to unlock the Monkey Invaders mini-game.
Hold R2 during Monkey Kombat to display the moves that can be used.