The following are known Action Replay Codes for Rugrats: Castle Capers 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
ec5eddf9
564b958d
ca80e61f
d1424e6c

Max Diapies
40cfe97f
7d95799e

All Items Collected
ed04324b
ae5a865b

Max Score
3226d1f2
a4f936cc
ed66a7a3
d6f21e81
0978f4ff
b3601c9b
4413de79
9cad65c1