Hard mode puzzles:
Beat all 25 Normal mode puzzles.

Special mode puzzles:
Beat all 25 Hard mode puzzles.

Mania mode puzzles:
Beat all 25 Special mode puzzles.

Chao!:
Beat all of the Stage Challenges to transform the mice into chao from Sonic Adventure.

NiGHTS!:
Beat all of the Mania Mode puzzles in one player mode to transfom the mice into NiGHTS angels.

Toggle Graphics:
The graphics may be toggled in the options menu after the respective puzzles have been cleared.

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. Some advantages of the Dreamkey web browser include:

-Better list interface with arrow bars, which makes it appear more like a computer web browser
Supports Flash 3.
-Better Javascript than the Planetweb browser.
-Ability to send and receive e-mail 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

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

No Kwyboard? No Problem:
If you dont have a keyboard how will you type in Ctrl + 0 to use the dreamkey browser. here is how you can bring up the url bar without a keyboard: 1) Make sure you are in the Hompage Section of the game 2) While holding A press start ten times (unlocks everything) 3) Then place cursor over the status bar (bar at bottom of screen) and press A + B togther while cursor is over the status bar. The URL bar should pop-up If it didnt then Try A + B again. 4) After that hold start + B to bring bookmarks up. start+x brings up history. Start + A brings up saved addresses 5) X + is to go click simultaniously to skip many pages.

Thanks to Revolution readers Anuj Kumar, Grant Latham, Jason Marcelle and Ricky Levy!