The Rumble Pak is a cartridge whick can be inserted into the back of a Nintendo 64 Controller. In certain games, the Rumble Pak feature will allow the Controller to shake. In the game say there was an earthquake inside the game, the controller would start to vibrate then. Because of the new Rumble Pak feature, they rereleased games in Japan like Super Mario 64. The Rumble Pak was released on April 1997 in Japan and latter came out in July in the USA.