Daily Training's Training Unlockables
Perform the following tasks in order to unlock new contents.

Hard mode for Calculations x 100 game - Get 11 stamps
Hard mode for Head Count game - Get 9 stamps
Hard mode for Triangle Math game - Get 17 stamps
Head Count game - Get 3 stamps
Low to High game - Get 1 stamp
Stamp Designer Option - Get 7 stamps
Syllable Count game - Get 2 stamps
Time Lapse game - Get 15 stamps
Tips Option - Get 5 stamps
Triangle Math game - Get 13 stamps
Voice Calculation game - Get 19 stamps

Easter Egg: Glasses, Glasses
On the main menu say "glasses glasses" into the microphone and Ryuta Kawashima will perform a "funny" animation on the left screen.

Easter Egg: Doctor
Say "doctor" into the mic at the title screen and Ryuta Kawashima will laugh or scowl.

Easter Egg: Big Stamp
If you complete three brain challenges in a day, the stamp used to keep track of your progress will be bigger.

Brain Age Check Selection
Go to the Daily Training section and select your name, press and hold [Select] and pick Brain Age Check. This will open up a selection menu that lets you choose which three challenges you want to complete for the age check.

Sudoku Advanced Mode
You can unlock the Advanced level of sudoku puzzles by completing 48 of the puzzles in Basic and Intermediate modes - a total completion percentage of 40%.