Shadow of the Colossus Easter Egg - Titular Title Scene in the Game

When you approach the first Colossus in the game, you will see his feet walking by.

Then, when the battle begins you shoot him with the arrow. When he stops, run up to him.

Jump onto his left calf (if you know where the weak spot is) when you stab him in the calf you can jump down and stand in his shadow. Stand in his crotch area shadow and your character will turn and look at the camera and say "Damn! I guess I'm standing in the 'Shadow of the Colossus!" and then laugh like the Disney character Goofey.