Unlock the following characters with the help of these cheats:
Elisa: complete the game with a "Medic" rating of 80, play it for the second time and save the game. Exit and restart.
Major Zero: you should have a Metal Gear Solid: Digital Graphic Novel saved game file on your Memory Stick. Complete the game and save after the credits. Now, restart the game and go to a save point. Then, exit the game completely and restart your console. Finally, load your game.
Null: just kill Null by health or stamina depletion with the MK22 in both fights. After that, complete the game and save after the credits. Then, you have to restart it and get to a point where you can save the game. Exit the game completely and reload it.
Python: use a tranq gun and stamina instead of health depletion when going to deplete him. In this case, you will see a different intermission sequence and unlock Python.
> Teliko: have a Metal Gear Ac!d saved game file on your Memory Stick and then complete the game. Save it after the credits and restart. Save it again and exit the game completely. Make a restart.
Venus: have a Metal Gear Ac!d 2 saved game file on your Memory Stick and successfully complete the game. Save it after the credits and restart. After having saved, exit the game completely. Restart your console and load it again.