The following are known Action Replay Codes for Teenage Mutant Ninja Turtles 3: Mutant Nightmare on Nintendo GameCube (GCN).

Master Code – Must Be On
WTG4-6RDK-FUHN9
QDVA-JQ1F-GWHND

Infinite Health: All Turtles
C2T8-5Y76-KJGDZ
KRB4-AJUJ-G1YBK
59PV-G8EN-6FGXH
63Q2-839B-5RD8U
7Y78-5GAU-QKC8P

Infinite Shruriken: All Turtles
4QXR-FQTR-DBAT7
827E-8MBR-2AD6V
0XXN-7E5K-JYQA3
39V8-1TPK-QTNVB
GTYU-VPQF-QY924

Infinite Crystals
CD5Z-K2UA-EMRCX
7028-35P3-U95UV

Unlock Challenge
6CDP-HBGK-F0NFQ
6N9X-ZATJ-YN719

Unlock Turtles in Time Arcade Game
5DNC-T99N-TY5QG
CBU7-6Z59-FW1QV

Unlock Movie Viewer
2NAD-G1TX-3ACKE
BU5M-XXPW-KTMM0