Instructions
From Game Menu
Launch "Animal Crossing: City Folk," and then press "A" on your Wii Remote from the main menu.
Press the "A" button to select "Other Things" from the subsequent menu options.
Press "A" to select the "Tear Down House" option. This action erases all your game's progress.
Select "Wipe it Out" from the ensuing confirmation dialog to effectively remove your current game account.
From Wii Menu
Click "Wii Options" from the console's main menu, followed by "Data Management" from the next screen.
Click the "Save Data" option, and then click "Wii."
Click to select the "Animal Crossing: City Folk" icon, which looks like a cat's face.
Select "Erase" from the following dialog options, followed by "Yes" to confirm your actions.