You can find the code in one of the Pyramid Levels. Its in the background like hieroglyphics.
The code is: Up, Down, Right, Left, Up, Down, Right, Left, B.
Insert this code when you press pause and the Achievement pops. It also gives you 999 free lives. Very useful in helping you practice the game because this code only works in story mode. You'll have to beat arcade the old fashion way.