The following are known Action Replay Codes for Nicktoons Racing 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
28c4f03e
ac9280e5
51755916
e9041c4a

Infinite Retries
3d3713e6
384bd907

Start on Last Lap
ff33ed1b
1874cbac