When you beat the game go to mission select and you will have unlocked a new level called Museum.

Go into it and it is a museum with all the characters set up (like a museum!) and they move, but when you get close to them then they freeze and turn back frozen.

Anyways, go to the front of the information desk (it will have information on the front) there is a button there.

Look at it and it will say do NOT press. Press by looking at it and holding X.

All the frozen guys in the museum will come to life and kill you. Even Captain Price and all the good guys!