To get this hidden mini-game, save after you get arrested by Ocelot. Para-medic will talk about the movie Dracula as Snake falls asleep. After that, turn off your ps2 and than go back to the save file. You will be in a game called "Guy Savage" that is similar to Devil May Cry. You will be playing as a guy with white hair and two hook swords. After the mini-game call Signit and he will have a very "interesting" conversation about a nightmare he had. This will not work on the Metal Gear Solid HD Collection on the Xbox 360 and PS3.
MGS3 Snake's nightmare