- San Fransokyo Institute of Technology's most illustrious alum and owner of the biggest technology company in the world, Krei Tech, is always on the hunt for the next big thing. Krei attends the showcase at San Fransokyo Tech and is overwhelmingly impressed by Hiro's ingenuity.
Alistar Krei is a somewhat morally complex man. As a business man, he's always on the hunt for something new and uses his wealth and intelligence to create amazing inventions that would earn him money. He even had connections with the government and would often sell some of his bigger inventions to them. However, as Callaghan stated during his introduction, Krei's business practices are somewhat questionable; he has been known to cut corners and ignore sound science in order to achieve his goals. This was demonstrated when he was warned that the transportation portal was malfunctioning but proceeded to test it with Abigail as the test subject, only to have the machine fail.
It can be assumed that as a businessman, what mattered most to him was making money by being profitable and taking risks with his inventions (some of which were unstable) without understanding the consequences of his actions. He seems to be the kind of person that is not usually rejected and not very receptive to it, as shown when Hiro rejected Krei's offer to buy his Microbots, he was clearly disappointed, somewhat bitterly saying that he thought Hiro was smarter than that before coldly handing back the Microbot he took. He also seemed to think that money was the answer to everything, as he continued to bombard Hiro with buying his invention, saying he would give him more money than any fourteen-year-old could imagine.
However, despite all of this, he did not seem necessarily evil as he did not seem to mean any actual harm towards Abigail and never committed any actual felons towards anyone―he just simply never considered the consequences of his actions. Though he did state during his toast to his company that there were a few setbacks, it is unknown whether or not he was actually referring to Abigail at all or possibly other people harmed by his inventions. He seemed cowardly as he openly feared Yokai and stated that he would be willing to do anything for him, but Yokai wanted his revenge. He is also shown to take pride in his company, having built it from scratch through hard work over the years.
Krei first appears at the San Fransokyo Institute of Technology convention, where he was conversing with a young inventor about his invention before noticing Hiro's Microbots. He quickly takes interest and attempts to have Hiro sell him the Microbots, but Callaghan intervenes, claiming that Krei only uses science for selfish reasons and subtly manipulates Hiro into refusing Krei's offer. He then leaves, angry and disappointed. Shortly afterwards, the showcase hall catches fire, resulting in the deaths of Hiro's brother Tadashi and apparently Callaghan.
Later, while Hiro is tracking down Yokai in the abandoned warehouse and after surviving a car chase from the masked man, he shows his friends a symbol of a bird in a circle which he noticed plastered on a map on the wall of an abandoned warehouse where Yokai had been multiplying the microbots. Hiro shows this symbol to the team after they narrowly escape the car chase. This makes Fred believe that Krei is really Yokai, though everyone else dismisses this idea as it would bring Krei negative attention and be too risky for his public image.
Hiro and the team head off to an island off the coast where Baymax tracks Yokai's location (having scanned Yokai's body) which turns out to be an abandoned Krei lab. As the team explores the lab, they discover an old computer with the same bird symbol Hiro had seen earlier. It then demonstrates a video of Krei performing a demonstration of a portal that can be used to teleport. He first uses the general's hat as an example, which was a success and next tried the same thing on a human being, who in this case was Abigail. One of Krei's scientists revealed that a "slight irregularity" had appeared in the portal's containment field, but he dismissed this and had the scientists proceed. Unfortunately, the experiment failed as the portal began to malfunction and suck everything in with it. Krei was then forced to shut his experiment down and abandon the lab under quarantine. This incident would also later earn him the wrath of Callaghan, as it was presumed that his daughter Abigail, who was the test subject, had died and he blamed Krei as the latter had proceeded with the experiment despite knowing that there were malfunctions, thus indirectly "killing" her. This made Hiro and the team believe Krei became Yokai in an attempt to steal back his research.
However, when they unmask Yokai, they are shocked to see that he is actually Callaghan, who had used Hiro's microbots to survive the fire and left Tadashi (who had entered the building to save him) to die. After he escapes and Baymax calms down Hiro, who had burst into anger and tears after learning that Callaghan did not have remorse for causing Tadashi's demise, the team watches the rest of the uncovered video recordings to get some answers, realizing that the test subject was Abigail, who was Callaghan's daughter and that Callghan was seeking revenge against Krei for the accident.
Callaghan attacks Krei during his latest ceremony as he reveals his plans to take away everything precious from Krei after he caused the accident that took away his daughter. Krei begs for mercy, saying it was an accident and that he will give Callaghan anything he wants. However, this only angers Callaghan as he states that he wants his daughter back. The Big Hero 6 intercepts Callaghan and attempts to reason with him, acknowledging his loss and how his daughter would not approve of his actions. Callaghan expresses regret for a moment, but Krei's cowardice causes Callaghan to resume his plans and pins Krei to a wall while he battles the Big Hero 6. Krei is soon freed from the wall, but the portal remains active. According to Krei, the portal's container field is failing which means that the portal will destroy itself. Before they move away from the portal, Baymax detects Abigail, alive but in hypersleep. When Hiro opts to go save her, Krei objects, worried that Hiro won't make it back as the portal is destabilizing. However, Hiro assures him by telling him that "someone has to help". Krei then watches as Hiro and Baymax enter the portal to retrieve Abigail and Hiro comes back with Abigail safe at hand.
After police and paramedics arrive to care for Abigail and arrest Callaghan, Krei is seen talking with the police about the incident and catches a glimpse of Abigail being wheeled towards a waiting ambulance.
Krei is last seen in the film's credits, where he opens a showcase hall in honor of Tadashi, apparently in consideration for the young man's sacrifice.
Alistair Krei returns in the series as a major character. He remains the most powerful man in San Fransokyo, and is often in the midst of testing or promoting a new invention made by his company. Though the ending of the film implied that the incident with Callaghan may have humbled Krei a bit, this is not the case—Krei is every bit as arrogant and careless with technology as he has always been. His position of power, access to technology and somewhat underhanded way of treating others makes him a recurring target to various villains, most of whom serve the mysterious Obake. He is repeatedly rescued, however, by Big Hero 6. The relationship between Krei and the team is explored throughout the series, and most interactions seem to suggest that they do not care much for one another. Krei has shown a level of gratitude for the heroes by agreeing to keep their identities a secret, but even this is not concrete; in "Aunt Cass Goes Out", Krei threatened to expose their identities should they refuse to help work out a kink in one of his latest inventions. Unbeknownst to Krei, his actions throughout the first season would go on to play a vital role in the grand schemes of Obake.
In season 2, Alistair Krei was shown to be an expert wilderness survivalist in "Muira-Horror!", having been in a scout troop as a kid. When confronted by the mutated Ned Ludd, who had been transformed into the Hibagon by Di Amara, it is his skills that help him, Go Go, and Hiro to escape serious harm by the monster, as he knew the best ways to hide from danger and the trails through the forest. Additionally, after Go Go had twisted her ankle, Krei constructed a brace for her ankle out of vines and twigs that allowed her to walk again.
- Alistair Krei is the third Disney character from the Disney Animated Canon to be voiced by Alan Tudyk, the first being King Candy from Wreck-It Ralph, and the second being the Duke of Weselton from Frozen. However, he is considered the first character not to be portrayed as an antagonist, despite having a hand in creating the film's true antagonist. Before the film was released, Krei was rumored by fans to have been Yokai. Because of this, Krei is actually a red herring, similar to the Duke of Weselton.
- The logo he uses for Project Silent Sparrow greatly resembles the 'Mockingjay' symbol from Suzanne Collins' The Hunger Games trilogy of books.
- An interesting thing to note that, when Alistair Krei gave Hiro back the microbot before he left, it was the same microbot that Hiro and Baymax used to track down Yokai, thus leading them to create Big Hero 6 to bring Yokai to justice. If that's the case, Krei unknowingly helped Hiro find out who killed Tadashi.
- Alistair Krei could be considered to be a subversion of a Disney villain who appeared good at first. In this case, Krei is assumed by the audience to be the real bad guy, but is revealed to be benevolent (even if he's not without flaws).
- In one of the first drafts of the script, Alistair Krei would actually have been Yokai's true identity. In this version of the script, due to the fact that the development of a pioneering defense project costed several times more than it was supposed to, and his company would be on the verge of bankruptcy because San Franksokyo's mayor refused to use it on the town, he would have become Yokai in order to create a menace to the city, in order to force the mayor to buy the project from him. He would have brainwashed and used Professor Callaghan and Tadashi, who would have survived the explosion as scapegoats. This idea was scrapped as the production team felt that Krei being the villain would not have enough impact on the story.
- Alistair Krei is one of the few people aware of the team's true identities.
Big Hero 6
Big Hero 6: The Series