After collecting certain amounts of stamps, you can unlock special things:
Choose one of the training modes at the menu. Get your stamp for the day then turn off the Nintendo DS. Turn on the Nintendo DS and change the date to the next day. Turn off the Nintendo DS so that your changes can be saved. Keep repeating this until you unlock all the training modes. When you have unlocked them all, turn off the Nintendo DS and change the date back to the correct value. This may effect your graph but you will still have all of the training modes unlocked.
Select the "Training" option at the "Personal" main menu. Scroll to the bottom of the list and select the last "???" option. the Virus Buster mini-game is a variation of Dr. Mario.
Choose your profile and go to the options menu with the "Brain Age Check", "Daily Training", etc. options. Hold Select and choose "Brain Age Check". You can now play any Brain Age Check exercise.
Stamp Unlockables for US version:
After every training exercise, click on the animation that corresponds with your speed (for example, walking, bicycle, car, etc.) to hear a cute sound effect that goes with it. The walker whistles, the car beeps, the train honks, etc.
Hold Select then choose "Graph" to see the top three of each exercise and evaluation.
Say the following phrases at the title screen to change the Doctor's expression.
Say "Cilantro" and he will make a unhappy face.
Say "Pickled plum" and he will make a sour face.
Say "Brain Age Two" to make his head swell.
Say "Doctor" to make him laugh.
If you go on multiplayer mode with at leats 3 players, you can select the Picture Drawing mode and even though it tells you what to draw, you can anything. For example, if it tells you to draw Los Angeles, you can draw a pony, hobo, weird button and etc.