Go to the Arcade level and look at the background. If your camera view is on the right side, you should notice a person whose back is towards you. He will be playing on one of the machines and will have the Atari symbol on the back of his shirt.
In Multi-player mode, enter any game with you and a friend. At any time during your opponent's turn, press any direction on the D-pad. Their Wiimote will then say "Jenga" in different tones every time you do so.
When playing a game with power-ups and you get the earthquake, take out a block. When you are getting ready to place it down, drop it when the earthquake is still rumbling. If done correctly, the rumbling of the earthquake will not stop until you go to the game menu.