Chu Chu Rocket cheats and cheat codes for Dreamcast

Transform to Sonic Adventure Chaos
Finish each of the 25 challenge mode stages

Transform to Nights angels
Finish each of the 25 mania mode stages

Unlock Chao in the game: Finish all 25 levels in Stage Challenge Mode
Unlock Hard mode puzzles: Finish all 25 Normal mode puzzles.
Unlock Mania mode puzzles: Finish all 25 Special mode puzzles
Unlock Nightopians in Puzzle mode: Finish all 25 Mania puzzles
Unlock Special mode puzzles: Finish all 25 Hard mode puzzles.

Taunt opponents:
Press R or L during the battle.