The following are known Action Replay Codes for Tamagotchi on Nintendo Game Boy / Color (GB / GBC). These codes were also known as GameShark Codes and in most cases will work on both devices.

Device Compatibility: Action Replay & GameShark

Max Age
013206d0

Max Life
010508d0

Max Body
01050ad0

Max Deed
01050bd0

Max Weight
013207d0