AUTO's personality resembles much of the personality of HAL 9000 from 2001: A Space Odyssey. As a machine, he shows no kind of emotion and just complies with the orders that have been given to him by the Chairman of Axiom Corporation, through the A113 Protocol. As such, because of his programmed orders, he also can be quite ruthless as to his pursuit of his orders' success, even if it means forcing the human crew to comply against their will.
700 Years Prior to WALL-EEdit
700 years before the events of the movie, the megacorporation Buy n Large (BnL) was at fault for making the planet's toxicity levels drastically high. It was so high, in fact, that the president & CEO of Buy n' Large, Shelby Forthright, had given a directive to A-113 in the year 2110, as a lustrum earlier (year 2105) was the origin of the cleanup operation, which ended in bitter failure. The directive was, basically, to prevent any attempt to return to Earth unless, sometime in the near future, life was proven sustainable for human populace. The judgment on whether or not Earth was viable for living would be based on signs of plant life (it can be guessed that because there was not any plant life, which probably went extinct due to the toxicity levels, Shelby claimed Earth unfitting for human habitation).
All Autopilots, including AUTO himself, had taken the directive literally. It is presumed that AUTO took the directive as: "Prevent any attempt to return to Earth at all cost", when the mission actually meant: "Do not return to Earth unless it is proven sustainable for life once more". Because of AUTO's mistake, humans had remained in space for centuries. The only thing left to remain on Earth were the WALL-E and incinerator units, who were to clean up the tons of garbage left on the planet while the humans escaped to outer space.
Of course, a lustrum after 2105, the WALL-E and incinerator units were either destroyed by the overload of work or they were shut down because they were too slow in the cleaning. Either way, 695 years later, only one WALL-E unit, at the age of 700 (because WALL-E and incinerator units were invented circa 2105), would still be functional either because it was not shut down or it survived from pieces of its similar units.
By this time, more specifically by the year 2805, humans still remain in space and are morbidly obese because of extreme bone deterioration and rely too heavily on the technologies upon the Axiom. AUTO is still bent on following his directive and has become the commander of the Axiom because Captain B. McCrea does little other than tell the morning announcements and watches over the ship, awaiting for an Extraterrestrial Vegetation Evaluator Probe that scans Earth for any signs of plant life which comes back positive and being left in the dark about AUTO's true colors.
When one specific EVE does indeed return positive, the "A-113" is clearly seen in AUTO's eye and, thus, AUTO nabs the plant from EVE without her knowing it and gives it to his right-hand lackey, GO-4, from there to try and discard later on. Then, when EVE is brought up to B. McCrea's room, she doesn't realize she was empty-handed until when AUTO scans her and finds nothing. After McCrea declares a false alarm, all returns to normal and EVE is then named faulty by AUTO and by the Captain as well. GO-4 and MVR-A transport bot then take EVE to check for evaluation.
After a while, the Captain scans the dirt that WALL-E left behind, instantly striking his curiosity and asks his main computer questions about "Earth", "Ocean" and all other subjects he had no clue of. AUTO becomes apparently suspicious of that action, now that the Captain is armed with knowledge of what AUTO kept his robotic voice box shut about and thus, they promptly call it a night, but not before the Captain asking what "dancing" was, which the computer responded to.
All this would later trigger the mutiny of AUTO: when McCrea was busy watering the plant, caring for it like a gardener would and then, when he spoke those words, he looked at the globe representing Earth before the events of the movie and then at the yellow ball of high toxicity levels, which was still Earth, thus their home, nonetheless (i.e., in McCrea's eyes), stating that they had to return to Earth. McCrea thus calls AUTO to the room to get him to put the plant in the holo-detector so they could hyper-jump to Earth.
When AUTO sees the plant that he thought was disposed of, he then displays the directive again and declares that it is not necessary to return to Earth. However, instead of giving AUTO the plant, McCrea then merely tells AUTO that if he wouldn't do it, McCrea would do it himself. AUTO then stops him and insists that McCrea hand over the plant, which McCrea responds by telling him to move out of the way. AUTO continues by saying they cannot return to Earth and when questioned by McCrea, AUTO refuses to answer, as it is classified and when McCrea pushes the matter by saying that AUTO is not allowed to withhold details from the Captain, AUTO tries to nab the plant from him but McCrea keeps it at bay from him. Finally, McCrea demands that AUTO tell him what was so classified about that matter, saying that it was an order. AUTO finally relents and shows him what was classified and what he was left out in the dark about.
On the video was the events of 695 years ago (as the Axiom was sent into space 2105), was CEO and President of Buy N' Large, Shelby Forthright, obviously embarrassed beyond reason about his failure to try to save Earth himself. By that time of the video, it was guessed that "Operation: Recolonize" had become a failure because even with the WALL-E units trying to do their best, it was nothing more than unrealistic to have the Earth clean in 5 years due to the many forms of pollution and liter and all but one WALL-E had been shut down or overwhelmed. To add fuel to the fire on his shame, Shelby then says to all Autopilots that it would be easier for humans to remain in space and that life was no longer good for Earth due to the toxic levels. Shelby then leaves with the same directive given 695 years prior to the movie, A-113, and declared that Autopilots are in charge of the ship, would be in total control and returns to Earth would be denied and Shelby leaves thereafter. After the clip, McCrea then asks when the message was sent out and the computer replies 2110, he calculates nearly 700 years ago.
McCrea scoffs at the President of BnL's words and says that things have changed and the plant was proof of that and further backs up his point by saying the plant was alive and growing. AUTO says that is irrelevant, McCrea then argues that it's all too relevant because back at the place was their home and saying that McCrea can't just sit there and do nothing (which is what most of the people and himself have done, obviously), which he confesses that is all the people and himself have ever done: nothing at all. AUTO then declares he must follow the directive, which frustrates McCrea. McCrea then stands up to AUTO and declares that they are going home whether or not AUTO liked it, which AUTO did not. He then staged a mutiny.
With GO-4 at his side, it seemed like he had the upper-hand, until WALL-E appeared from the garbage chute. AUTO then demanded that WALL-E give him the plant, which WALL-E doesn't and stores it away in his body. WALL-E then gloats at his victory, but AUTO just responded by zapping him with a taser and knocking him away in the Garbage chute. AUTO then shuts off EVE and GO-4 promptly throws her in the Garbage chute. AUTO then imprisons McCrea in his quarters.
Just when AUTO thought that he won that battle, the Captain then hot-wired the monitor to send out a message of him holding the "plant", which was a holographic image of WALL-E holding it and taunts AUTO by saying that if he wanted the plant back, McCrea then says "Come and get it, blinky." AUTO then scans the room looking for McCrea to reclaim the plant. McCrea then ambushes AUTO and somehow winds up in the command deck, where AUTO is ruling everything, by squeezing through a hole in the ceiling.
McCrea and AUTO then battle for dominance and AUTO easily knocks McCrea away. Despite the fact that McCrea was without his chair, he stood up straight and ambushed AUTO again after seeing AUTO crush WALL-E with the holo-detector. It is possible that McCrea, after seeing WALL-E crushed by AUTO, found the will to stand up and continue the battle. GO-4 tries to help AUTO, but only winds up getting himself knocked back by the fight, flung off the tower from the impact of the Captain hitting him and thus died soon afterward because he crash-landed besides a pool, destroying him.
AUTO then fires the taser again, but before he can try to zap McCrea, the Captain then sees the only way to subdue AUTO was to turn the "Auto" switch to "Manual", in which McCrea ends AUTO by flipping the exposed switch to manual pilot. AUTO then gives one last "No..." and shuts off, leaving McCrea in control of the Axiom and, in the end, the end of the line for AUTO.
AUTO is unusual among many Pixar antagonists, as he was merely following orders rather than trying to cause malice or harm to the protagonists.