Unlimited power for all characters:
Enter this code while in the "Extras" menu: Circle, Left, Right, Circle, Square, L1

Unlock all Clichés:
Enter the code while in the "Extras" menu screen: Left, Square, right, Circle, right, L1

Unlock all Movies:
Enter the code while in the "Extras" menu: Square, Left, Square, Right, Circle, R1

All outfits and trophies for Marge:
While in the extras menu type in Triangle, Square, Triangle, Triangle, Square, R3

Unlock Lisa's Outfits & Trophies:
To unlock all Lisa-related outfits and trophies, insert the following code while browsing the main menu: Square, Triangle, Square, Square, Square, L3 (click left analog stick).