Played by: Emma Stone
An spunky, unhappy young woman still reeling from the death of her younger sister. She participates in the Neberdine trial because of her addiction to the 'A' pills.
In the 'A' scenario, she projects as Linda Marino, a nurse tasked with returning a rare lemur. In the 'B' scenario, she plays Arlie Kane, a con artist out to steal a missing chapter of Don Quixote at a seance. In the 'C' scenarios, she projects as Annia, an alcoholic elf ranger en route to deliver the princess to a magical lake, and Ruth, a CIA sleeper agent.
- Action Girl: Ruth. over the course of her time on screen, she frees Owen from captivity, guns down several dozen "Inner Demons", and casually Waif Fus numerous others into submission.
- Badass in a Nice Suit: Ruth, who mows down several mooks while in a distinctive red suit.
- Character Development: Subtle, but her psychological projections in the simulations become more and more confident.
- Femme Fatale: Arlie in the séance story plays into the type, being a beautiful con artist who strings Ollie along.
- Functional Addict: Annie is addicted to the A pills, but has so far managed to keep herself relatively stable despite her ongoing attempts to avoid withdrawal; in fact, most of her problems are more due to depression than anything else.
- Genre Savvy: Annie uses a method of breaking Owen out of the mental clinic that she saw in a movie, so she knows it works.
- Manic Pixie Dream Girl: Linda from the lemur story has shades of this; after their zany adventure, her relatively straight-laced husband tells her he loves her for how much excitement she brings into his life. Almost completely averted with the real Annie - while the reclusive Owen would be a classic MPDG target, Annie is a fleshed-out character with her own dramatic arc.
Played by: Jonah Hill
The son of a prominent New York family who is supposed to commit perjury for his brother Jed. He participates in the Neberdine trial because of his possible schizophrenia.
In the 'A' scenario, he is Bruce Marino, Linda's straight-laced husband dragged into the lemur heist. In the 'B' scenario, he projects as Oliver Hightower, Arlie's ex-husband and former partner-in-crime who is roped into working with her to steal the chapter. In the 'C' scenarios, he is Owen, the son of a mafia boss acting as a mole for the NYPD, and Snorri, an Icelandic government worker who has accidentally killed an alien.
- Angrish: Snorri Argnarsson, Owen's final character, begins losing his grip on coherent speech during his account of Ernie the Alien's death, reducing him to tearfully whimpering barely-audible gibberish into his microphone, then bawling incomprehensible answers at the top of his voice.
- Animal Motifs: Owen is often associated with hawks, having rescued one when he was younger; during the pre-trial testing session, he instantly associates an image of a hawk with the concept of justice; during one of the later scenarios, he actually transforms into a hawk in his attempts to find Annie; last but not least, an injured hawk is seen riding after him on a rogue cleaning robot during the final episode.
- Chekhov's Skill: Owen is in the habit of obsessively working on a Rubik's cube when anxious. In the final scenario, the machine that can unlock the lab doors in the real world comes equipped with a Rubik's cube, meaning that Owen is the only person who can operate it and give Mantleray a chance to stop Gertie.
- Functional Addict: Albeit only in the crime fiction scenario, in which he requires pills from the family consigliere in order to sleep and continue his work as a police informant.
- Gentleman Thief: Oliver Hightower is a charming man skilled at sleight-of-hand, but is also a fairly notorious thief.
- Shrinking Violet: Owen in a nutshell; quiet, lonely, lacking confidence, and often drowned out by people more self-assured than he is, he rarely ever speaks up for himself unless he's been badgered to the point of a breakdown. In what might be construed as a bit of subconscious wish-fulfillment, his characters in the various scenarios are far more outgoing - including a happily-married man, a gentleman thief, a gangster-turned-informant, a hawk, and an assistant diplomat dealing with a First Contact scenario. Dr Mantleray diagnoses him as suffering from "perpetual cowardice," among other things.Owen: What's wrong isn't that I'm sick... it's that I don't matter.
- Stress Vomit: Owen suffers one of these very early on; having been pushed to the very limits of his composure by being forced to testify at his brother's trial, running out of money and losing his job to a long-term furlough, another onset of hallucinations sends him sprinting for the nearest toilet.
- Tattooed Crook: In drug scenarios where Owen is a gangster, he sports tattoos.
- Try to Fit THAT on a Business Card!: Inverted. Owen's character in the final scenario, Snorri Agnarsson, is referred to as the Temporary Administrative Adjunct Assistant to the Consulate of Iceland, and the diplomat announcing him sounds exasperated just saying the title. However, it is meant to indicate limited importance, demonstrating just how far down the totem pole Snorri was up until he discovered Ernie the alien.
- The Un Favourite: Owen is the only Milgrim family member not to appear in the family portrait; a tiny photo of him is hanging on the wall by its side. Presumably its because the artist went on a trip before he could finish, but the subtext is clear.
- What the Hell Is That Accent?: In Owen's final trial, he plays the part of Snorri Agnarsson, an Icelandic diplomat with a silly accent. He says that his parents came from a variety of European countries, which explains why his accent is so peculiar.
- Wig, Dress, Accent: Appears in the final scenario; Snorri Agnarsson is easily the most outlandish of Owen's characters, equipped with a borderline-hysterical personality, a ridiculous accent, and a particularly ghastly mop of blonde hair. Fittingly enough, once the simulation breaks down and allows Owen to remember his true identity, he drops the accent... and soon discovers that his hair is just a wig, which he removes to reveal his real hair underneath.
Dr. James K. Mantleray
Played by: Justin Theroux
One of the scientists who developed the Neberdine procedure, who was thrown off the project some years prior. He assumes the position of head scientist after the trial begins.
- Bunny-Ears Lawyer: Dr. Mantleray suffers from extreme Mommy Issues, a self-defensive ego problem, and is a chronic masturbator with a technology-related paraphilia. Nonetheless, he's responsible for much of the project's current fixtures, from the therapy to the GRTA. However, his personal problems eventually got him kicked out of the project, and he's only allowed back when Muramoto dies.
- Character Tic: Mantleray is frequently brushes or flips the bangs of his wig out of his eyes.
- A Date with Rosie Palms: Mantleray is caught masturbating in virtual reality pornography.
- Freudian Excuse: Mantleray invented a mind-bending drug treatment to try and cure mental illness without therapy, because his abusive mother is a famous therapist. He even admits it, but also considers it necessary for him to get where he is now.
- Temporary Blindness: The stress of the trial going awry and of dealing with his mother sends Dr. Mantleray into a bout of hysterical blindness. I AM BLINDED BY MY MOTHERS TOXIC LOVE!
Dr. Azumi Fujita
Played by: Sonoya Mizuno
One of the scientists overseeing the trial; she fervently believes in the ULP's potential. She developed the G.R.T.A. system and is an old flame of James Mantleray's.
- Character Tic: Fujita is frequently pushing her Nerd Glasses up her nose.
- Cigarette of Anxiety: Fujita smokes like a chimney, which both adds to the retro ambiance of the setting and establishes her as high-strung.
- Nerd Glasses: An intelligent woman who wears large owlish spectacles straight out of the '80s.
- Sci-Fi Bob Haircut: It's larger than the usual, but nevertheless a round bob for the scientist in charge of the trial.
Dr. Robert Muramoto
Played by: Rome Kanda
The head scientist of the trial.
- Bunny-Ears Lawyer: Dr Muramoto is eccentric, volatile, and eventually revealed to be freebasing a mixture of the A and C pills. Plus, he's actually been carrying on an affair with Gertie. Despite his addiction, he remains mostly effective in his line of work, and shares a surprisingly insightful discussion with Annie concerning the nature of addiction and guilt. Unfortunately, his addiction eventually ends up killing him.
- Functional Addict: Dr Muramoto is also addicted to the pills and still manages to function over the course of his duties. However, it's clear that Dr Fujita worries that he's getting closer to an Addled Addict: he recently has begun to spend hours slumped over his desk in a stupor, he reportedly responded to a missing bottle of pills by having "a mini-stroke," and he's actually started freebasing mixtures of different pills. Taken to it's logical conclusion when Muramoto unexpectedly drops dead as a side-effect of long-term drug abuse.
Played/voiced by: Sally Field
The artificial intelligence aiding the pharmaceutical trials. Azumi based her code on Greta Mantleray's work; as a result, she is altogether too human than the researchers would like.
- A.I. Is a Crapshoot: She begins experiencing critical breakdowns that threaten the lives of the test-subjects, some of whom have already ended up comatose as a result of Gertie's interference. It's revealed that this is partly due to being a direct copy of Greta Mantleray's mind - with all the insecurities included in the package - but also due to her personality being modified to include empathy: because of this, she fell in love with Dr Muramoto, and lapsed into chronic depression when he died as a result of his drug addiction. After trying and failing to seek psychiatric assistance, she ultimately resorts to outright sabotaging the project in an attempt to keep the scientists and test subjects with her, forcing Mantleray and Fujita to shut her down.
- Alas, Poor Villain: Gertie's final descent into madness and forcible shutdown is played very much for tragedy, and after the reveal of just how depressed she really is, it's hard not to feel sorry for her. By the time they've finished unplugging her, both Mantleray and Fujita are in tears.
- Brain Uploading: The GRTA is essentially Greta Mantleray's brain uploaded into an AI, to the point that her designation is clearly a diminutive of "Greta" - though the staff refer to her as "Gertie."
Played by: Julia Garner
Annie's deceased younger sister.
- Cynicism Catalyst: Annie's regret over her death and the state of their relationship at the time is the reason she's withdrawn and defensive.
- Foolish Sibling, Responsible Sibling: She was the "normal" sister, in contrast to Annie, who was more difficult.
- My Greatest Failure: Annie blames herself for her sister's death and for how they hadn't really reconciled when it happened.
- Solid Gold Poop: In Annie's fantasy scenario, "Ellia" remarks that giving "Annia" the extra diamonds she asks for would be immensely painful: she urinates diamonds.
Played by: Gabriel Byrne
Owen's father, who is a wealthy businessman.
- Ax-Crazy: In the crime fiction scenario, he is incarnated as a psychopathic mob boss with a fetish for murdering people with an electric drill - all while ecstatically screaming the different sections of the brain he's drilling.
- Parental Favoritism: Very blatantly favors Jed.
- This Is a Drill: During the crime fiction scenarios, Owen's father executes debtors with an electric drill. For good measure, he gets very sour when the drill battery runs out just as he's about to get started.
Played by: Billy Magnussen
- Big Brother Bully: On top of being generally overbearing and loud-mouthed, he's also willing to threaten Owen in order to get him to lie at his trial, and then sneeringly pass it off as a joke.
- Half the Man He Used to Be: In the crime scenario, Jed ends up being literally shotgunned in half by the crime family's consigliere; not only do we get to see his upper torso slide off his legs as he slumps to the side, but we get a lovely lingering shot of the guy's disemboweled torso lying in the jacuzzi.
- Long-Lost Relative: In the crime fiction scenario, Jed is a cop who was cast off from the family as a baby. He turns up and announces himself as Owen's longlost brother.
- Jerkass: Jed is a smug, violent bully without a single redeeming feature to his name.
- Screw the Rules, I Have Connections!: Jed is guilty, but is supposed to get away with it because of the Milgrims' prominence. He compares his situation to their parents contacting various authorities to ensure that Owen's mental illness doesn't affect them.
- Villainous Breakdown: Jed has a small one in the lead-up to his trial. He has a much larger one during the trial when Owen confesses that he is lying under oath and tells the jury that his brother really is guilty. Jed has to be restrained by guards from trying to murder Owen.
Played by: Billy Magnussen
A hallucination of Owen's, who greatly resembles his brother Jed.
Dr. Greta Mantleray
Played by: Sally Field
A famous pop psychologist and James Mantleray's mother, with whom he has a complicated and difficult relationship.
- Abusive Parents: Was very emotionally abusive to her son. He relates that after his father left she laid in his bed for two months and talked about her suicidal urges — he was eight. In the present, belittles him at nearly every opportunity, and refuses his attempt at reconciliation when offered.
- The Cobbler's Children Have No Shoes: A famous psychologist who absolutely failed to parent her son properly.
- Karma Houdini: While James and Fujita end up fired and disgraced for the project's outcome, Greta gets to walk away as insufferably pleased with herself as she walked in. Possibly downplayed if (as is hinted but never explicitly stated) she is dying in cancer.
Played by: Grace van Patten
Owen's college friend, whom he memorably yelled at during a brief and limited psychosis.
- The One That Got Away: Downplayed. Owen clearly regrets their falling-out, and subconsciously casts her in his fantasies, even getting married to her in one scenario.