Instructions
Play the game until you reach level 1-8 of the "Poached Eggs" episode.
Roll your scroll wheel back to zoom out until the whole stage fits on the screen. You will now be able to see your birds on the left and the chest in the middle.
Launch one of your birds high enough into the air so that you have enough time to type before it hits anything. The reason for this is that the game will pause as soon as you press the "p" key, and launching a bird prevents that.
Left click and hold down the mouse button over the chest in the middle of the stage.
Type "open" with your keyboard before the bird hits the ground. The chest will open, rewarding you with a golden egg.