The following are known Action Replay Codes for The Fairly OddParents! Shadow Showdown on Nintendo GameCube (GCN).

Master Code – Must Be On
QGJQ-8Y21-TEFAV
VAGR-61Q2-M9M3T

Infinite Health
2WU4-2MNA-TBKPC
ZRDM-45M2-P6QU3
D03N-C8BF-XVYNK

Max Coins
YVRD-PFA0-E3HXE
9JH3-C6WR-B7BZN

Infinite Dash
UEDQ-1QAM-3V609
KQCD-W3WY-QQ3G2

Infinite Double Jumps
G3QB-FY2A-3VKFQ
E3JK-NXK3-G1Y1Z