Win time attack easily
Play as Wonrei and li-en and select them in time attack. All you have to do is keep pressing X to defeat your opponents. Watch out for Ponygon and Kanchome/Folgore, they can be devestating fighters.

Zeon and Deufo
Complete Zatch story mode to unlock Zeon and Deufo as selectable characters.

Laira
Collect all Event cards.

Zeno
Press Up(2), Down(2), Left, Right, Left, Right, Circle, X at the title screen.
Play as Zeno in story mode:
Press Up(2), Down(2), Right, Left, Right, X, Circle at the title screen.

Password mode
Defeat the 1st 10 opponents in Zatch Bell's story line to unlock the cheat-password option in the Bonus section.

Maestro
Win Time Attack mode 300 times to face Maestro. Defeat him to unlock him as a selectable character.

Mr. Riddles and Kido
Defeat Mr. Riddles and Kido in any story mode.

Milordo-Z
Collect all Spell cards.

Laila and Albert
Enter UCKAHEIT .

Mr. Riddles
Defeat Mr. Riddles in any story mode.

Victoream
Collect all Mamodo cards.
Play as Wonrei and Li-En:
Defeat Wonrei and Li-En in multi-player mode.

PS2 Cheats for Zatch Bell! Mamodo Battles

Zatch Bell! Mamodo Battles cheat codes

Zatch Bell! Mamodo Battles cheats