 In the original Playstation version of Metal Gear Solid, Colonel  Campbell tells Snake (and the player) to look for Meryls codec  frequency on the back of the CD case, obviously referring to the  case that the game came in. In The Twin Snakes, Campbell instead  says to look on the "back of the package". Many gamers that hadnt  played the original Playstation game were confused by this, as it  wasnt obvious that he was referring to the DVD