Head to the extras section of the main menu and insert the following code, which will give each of your characters infinite power: Circle, Left, Right, Circle, Square, L1.
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).
To unlock all of Marge's trophies and outfits, head to the game's main menu and insert the following password: Triangle, Square, Triangle, Triangle, Square, R3.