Go to B2 of the Shell 1 Core, then eliminate all guards and find the caged parrot. You can teach it to say "You must be Ames" by pointing the Directional Mic at it and pressing ACTION multiple times. Firing different weapons at the bird will also cause it to say new things. For example, Coolant Spray will cause the bird to say "This sucks".
While in the computer room on B1 of the Shell 1 Core with guards in it, if you shoot the bird, he will say "Enemy spotted, send reinforcements" and the game will enter Alert mode.