GLaDOS

GLaDOS (Genetic Lifeform and Disk Operating System) is a robot created by Aperture Science with artificial intelligence. She is a sarcastic and cruel entity who enjoys insulting others and showing off her power. She enjoys that humans are killable and show fear, and for this reason prefers using human subjects for her tests. Though she has no morals, she attempts to guilt her subjects to see their reactions for "science." She has a fear of birds due to one preying on her when she was in a vulnerable form (see potato image).

Once created, GLaDOS immediately attempted to kill every scientist in sight. In an attempt to lessen her psychopathic tendencies, Aperture scientists tried utilizing a morality Core, a device used to change the personality of an AI. Instead of attempting to kill humans, GLaDOS turned her attention towards science. However, her idea of science was using humans as subjects to test Aperture Science technology in deadly obstacle courses. GLaDOS locked down the facility and captured the employees of Aperture Science to use them as her test subjects.

While journeying through old Aperture facilities buried under the current building with her human test subject and rival, Chell, GLaDOS discovers that she was once a human woman named Caroline. Caroline was most likely uploaded to become part of GLaDOS against her own will at the request of her boss. This discovery alarms GLaDOS, who starts to hear Caroline's voice. After regaining her composure, with Caroline as part of her AI she acts more positively and kindly, even saving Chell from death. Afterwards, she claims to delete Caroline from her programming, but still acts uncharacteristically nice, so whether or not she still has Caroline's influence is unknown. Proceed with caution when dealing with her.