ChuChu Rocket!

Save pictures from the web:
You can save pictures onto your VMU while using ChuChu's Dreamkey browser. Place the cursor over the desired picture and press X + A on the controller.

Sonic Adventure Chaos:
Successfully complete each of the twenty-five challenge mode levels to transform the mice into Chaos from Sonic Adventure. 

NiGHTS angels:
Successfully complete each of the twenty-five mania mode levels to transform the mice into angels from NiGHTS. 

Hard mode puzzles:
Successfully complete all puzzles in normal mode. 

Special mode puzzles:
Successfully complete all puzzles in hard mode. 

Mania mode puzzles:
Successfully complete all puzzles in special mode. 

Taunt opponents:
Press L or R during the battle games to taunt your opponent. Hold L or R to choose which taunt to use. You can also taunt even after you have won at the congratulations screen.

Dreamkey web browser:
This trick requires a Dreamcast keyboard, and can be used as a replacement for the standard Planetweb browser. Go to the Homepage in the main menu. Once the Chu Chu Rocket title appears, press [Ctrl] + O on the keyboard. The URL bar will appear, which allows you to type in any Internet address. This is almost the same browser that the European and Japanese Dreamcast users have access to.

Some advantages of the Dreamkey Browser include:
Better list interface and has arrow bars, which makes it appear closer to a computer web browser.
Supports Flash 3.
Better Javascript than the Planetweb browser.
Ability to send and receive email with VMU files attached.
Higher on-screen color count than Planetweb browser.
Can Save Midi or Wav files to the VMU.
Pages appear to load faster.
Supports cookies.
Keyboard shortcuts
URL bar: [Ctrl] + O
Reload page: [Ctrl] + R
Bookmarks: [Ctrl] + B
Mail: [Ctrl] + M
History: [Ctrl] + H