This is a bit hard to do, so you'll need a little patience. Go to Adventure mode as Jigglypuff. Now, hold left and R. Jigglypuff will roll and put up the shield. Eventually, she will die. If you press start as she's dying, you'll sometimes get a strange camera view. However, repeat this until she dies in the way in which she smashes into the screen. When she does this, press start three or four times, but not repeatedly. When she comes back to life, make sure you don't press start. If everything was done correctly, the camera should be way lower than usual, and you'll find it difficult to navigate. If you die, the camera will return to normal.
Submitted by: Jesse