Hamtaro: Rainbow Rescue - Unlimited Acorns

Secret Coloring Picture at the Clubhouse:
Stand in front of the blackboard in the Clubhouse and press the A button. After reading the message, press the L, R, A, B buttons in this order and you'll receive a secret coloring picture.

Getting the secret picture 'Too Much Good Stuff':
Go to Hamstarr Manor. Behind Seed Pig-Out the one with Mean Oxnard there are three hamsters sitting behind a table. Talk to the middle hamster ONCE. Then, press the following buttons in order: B, L, A, B, A, R. You will receive the picture 'Too Much Good Stuff'.