In the last area in Tomb of the Ancients, on the dark spot n the third panel behind the "Technical Check-Up" door, press the buttons "B, Y, D-Pad Right, D-Pad Left, D-Pad Right, D-Pad Left" in that order. If you were in the right place when you entered the code, a crate will appear that allows you access to a hole in the wall. In this hole, you can view various secrets about the game.