Control crystal
Start the game and make sure you are on the "Interact" slot. You will see a crystal on the touch screen. Slide your finger across the touch screen. The crystal will start spinning.
Completion bonus
After you have completed everything in the game, check at the store every month or change the month on the DS system date until an object that resembles a tanning bed. Buy it and put it in your room. When you get in there, there will be a place to choose your skin color. The colors are green, yellow, dark gray, light gray, blue, red, pink, and orange. The color will wear off in one or two days.