The following are known Action Replay Codes for Hey Arnold! The Movie on Nintendo Game Boy Advance (GBA).
These codes were also known as GameShark Codes and in most cases will work on both devices.

These codes are for the U.S. version of the game.

Master Code – Must Be On
74c9fdd4
c4842f01
6feb18e3
3911d2b9

Infinite Health
dd60d5f9
7a037faa

Infinite Lives
70ead57d
c25cbc7a