While digging in the Red Ribbon's data, you find that all of Dr. Gero's androids have a code to enter in some sort of... Obedient emotionless state, the code being "Code 7-2-5 RR"

Knowing this code, you go to where Android 18 lives, wanting to try it out

While you're walking to the house, she spots you and comes out to confront you

Hey! Who are you!