GLaDOS was a creation of Aperture Science, a personality core designed exactly to be fitted as a central computer mainframe. The project began under the oversight of Cave Johnson over the company, and was an attempt to create a fully functional, advanced artificial intelligence which was originally intended to be occupied by Johnson as one of his attempts to cheat death. After it became apparent to Johnson that he may die of moon rock poisoning before development on GLaDOS would be completed, Johnson motioned for the personality core to be based on his secretary and best friend, Caroline instead.
After a decade's worth of hard work, GLaDOS was officially activated in 1998, as part of one of the many events during the company's "Bring Your Daughter to Work" day. Since she was able to take control of half of the facility's features, GLaDOS began killing most of its inhabitants by flooding the Enrichment Center with neurotoxin. However, only few if not only one of the staff such as Doug Rattmann had survived her attacks along with the series' main protagonist, Chell. The destruction of the company also coincided with an invasion of Earth, which had occurred two days after at Aperture's rival company, Black Mesa. This ultimately led to the negligence of the outside world from realizing Aperture's fate, as all attention had been diverted to Black Mesa and the aforementioned invasion.
Since the attack, she has managed the company to her limits. Her first test subject and the series' main protagonist, Chell, was given a warning of GLaDOS' true colors with the help of Doug Rattmann. She confronts GLaDOS in her chamber at the end of Portal, which allowed GLaDOS to develop an even deeper hatred for her after she was awakened in the beginning of Portal 2.
After Batman, Wyldstyle and Gandalf arrived at the Aperture Science Enrichment Center in search for the cake (one of the Foundation Elements), GLaDOS initially mistakes the heroes for Chell. When the the trio announce they are looking for a cake, she sends them to a course of nine test chambers. GLaDOS accuses them of cheating as they use keystones to pass the tests, rather than a portal gun. After the 9th test, GLaDOS brings them to her chamber where she tries to "entertain" them with crushers and neurotoxin. The heroes summon H.A.L. 9000 to distract her, giving them the time to solve the Chroma puzzle behind her to get the pieces needed to build a ramp and drive a vehicle into her. GLaDOS responds to this by sending them to an oven, where the cake is located, but it is also another test chamber filled with flamethrowers. After the heroes escape from the oven, she plans to send them to another test chamber featuring electricity, but X-PO opens a portal back to Vorton and the heroes make their escape, leaving GLaDOS to complain about being lonely.
After defeating the Tri, the trio returned to the Aperture Science Enrichment Center to ask for GLaDOS' help. She refuses, jokingly telling them to tell it to her morality core, before revealing that it was replaced with an amorality core. In response Wyldstyle replaces her amorality core with an actual morality core, preventing GLaDOS from acting on her violent impulses. She demands they replace her amorality core, but Batman says they will do so if she helps them. She reluctantly agrees, and appears on Vorton being examined by Egon Spengler. She asks the Doctor to repair her morality core, but he declines.
GLaDOS helps the heroes during the final battle by finding a safe way to Foundation Prime, and then giving the heroes a Rocket Turret to destroy part of the Baseplate.
After the final battle, she reviews information on Chell in her main chamber, singing the song You Wouldn't Know. After the song, a dimensional portal opens and her amorality core drops into the chamber. GLaDOS strokes the core with her head.
“Oh. It's you. Again. I've hoped you have been eaten by a deer by now.”
— GLaDOS when meeting Chell in the Portal 2 Adventure Mode.
“I suppose you think you're clever, circumventing my meticulously-planned tests with your ability to fly? If you're happy cheating yourself then, of course, that's entirely your prerogative, but I hope you realize that such behaviour is of no benefit to science. Unless you are using science to fly. ... Actually, HOW are you flying? ”
— GLaDOS when the player travels through the yellow Shift portal in Test Chamber 01
“Please attempt to place the Aperture Science Weighted Storage Cube on the Fifteen-hundred Megawatt Aperture Science Heavy Duty Super Colliding Super Button.”
— GLaDOS after the player presses the Aperture Science Switch on the Victory Lift in Test Chamber 01
“Logic error detected. Subject should not have been able to move the Weighted Storage Cube in this way.”
— GLaDOS after the player uses a character with the Magic Ability to move the Weighted Storage Cube onto the Heavy Duty Super Colliding Super Button in Test Chamber 01
“You're doing very well... That is to say I suspect you were cheating in that last test. Cheating is wrong and, ultimately, the only person who loses when you cheat is yourself. For instance, you might lose your freedom. Or your mind. Or some teeth. I will be monitoring your behavior more closely in the future. Now, on with the next test.”
“Oh you fixed it. How... wonderful. You know, I was joking when I said it was impossible. That was part of the test and you didn't give up. You kept going despite knowing everything you were doing was futile, just like the inherent pointlessness of you're existence.”
“You must be very proud of yourself. You *SUBJECT NAME HERE* must be the apple of *SUBJECT'S FATHER'S NAME HERE*'s eye.”
— GLaDOS after the player guides both High Energy Pellets to the receptacles in Test Chamber 04
“For this next test, Thermal Discouragement Beams have been added in to the testing environment. Health and safety would advise you to avoid contact with these lasers, however, the Health and Safety office is closed today so please disregard that advice.”
“Oh look. It's my favorite thing in the whole wide world... Deadly Neuro-toxin. Be careful, you don't want to breathe too much of it in.”
— GLaDOS when the players reach the right area of Test Chamber 09
“What was THAT? It was all EXTERMINATE, and there was fire and explosions! I think I admire its attitude”
— GLaDOS after the Dalek exterminated the Sentry Turrets in Test Chamber 09
“I think you deserve recognition. Through cheating, ignoring the rules and destroying the Enrichment Center, you have completed this round of testing. Congratulations.”
— GLaDOS when the player presses both Aperture Science Switches in Test Chamber 09
“Welcome *insert party noises, here*. A party associate will be along shortly with your congratulatory cake for surviving... I mean... completing all of the tests. For now, allow me to entertain you.”
— GLaDOS at the beginning of her boss battle
It is revealed that she is the one responsible for delivering Shaggy and Scooby-Doo the box of LEGO Bricks for the LEGO Gateway and their mini figure versions, as well as a box of pizza at their doorsteps in the LEGO Dimensions - Scooby Doo Gameplay Trailer, though it's unknown how she was able to leave the Aperture Science Enrichment Center.
Ellen McLain reprises her role from the series in LEGO Dimensions.
Just like every Portal game, (this game isn't an exception) she sings an original song at the end credits.
GLaDOS is strongly reminiscent of H.A.L. 9000, the murderous A.I. computer of 2001: A Space Odyssey; even the single, red "eye" of the security cameras and Sentry Turrets are reminiscent of HAL.
HAL 9000 himself was summoned via Locate to converse with (and distract) GLaDOS.
GLaDOS means: Genetic Lifeform and Disk Operating System.
She was replaced by Wheatley, who downloaded her to a potato battery (PotatOS). This is referenced in the minikit build from the level Aperture Science.
She is one of the few LEGO Dimensions antagonists who do not work for Lord Vortech.
In fact, Batman, Gandalf, and Wyldstyle got her to help them fight Vortech.
GLaDOS is one of two bosses to be fought more than once, the other being Lord Vortech.