Danny Phantom: The Ultimate Enemy [GBA]

Credits
Successfully complete story mode.

Dash's Haunted Locker Mini-game
Enter DASH as a password.

Ghost Arena
Enter RUSH as a password. In it you can play as Danny Phantom or Dan Phantom.

Ghost Plasma Colors For The Phantom Termos
Green: Refills a bit of the life meter.
Purple: Refills a bit of the plasma meter.
Red: Refills both the life and plasma meters.

Hindin' Ghost Seek Mini-game
Enter SEEK as a password.

Levitation Mini-game
Enter JAZZ as a password.

Sam's X-ray Ecto Detector Mini-game
Enter ECTO as a password.

When to use the Phantom Termo
When you defeat a big ghost like the boxer ghost, it will leave a plasma mark. You can then use the Phantom Termo.

All Difficulties
Enter VLAD as a password to unlock the easy, normal and hard difficulty settings.

Clockwork's Time Quest/Mission Mode
To unlock Clockwork's Time Quest/Mission Mode, simply beat the game once on Normal difficulty. Once you do, go back to your saved game and Clockwork himself will fill you in on the rest. Then you're in Mission Mode. In this mode, you can also fight enemies from the past such as Skulker, Ember, and even The Box Ghost. This mode also has you do different things on the past levels to earn medals such as "Do NOT Use Plasma Powers" or "Beat 5 ghosts in under 30 seconds."