Examples of Foreshadowing in Glass Onion.
- The date given at the bottom of the screen in the very first scenes. It establishes that the film takes place during the height of the COVID crisis, but also ties in with Whiskey's birthday present from Miles. If you know enough about astrology to know when a Taurus is born, you can pierce Miles' lie about not leaving the island for a good long while the instant he says it.
- When Lionel's introduced trying to calm the concerns of his research team about Miles, he asks "But what can I do?" in an 'it can't be helped' manner. His team immediately says in unison, "You can tell him no!" The whole story starts because Andi refused to go along with Miles' schemes any longer, and the plot is driven by the other Disruptors' constant refusal to say 'no' to him and keep depending on him, right up until literally the closing scenes of the film.
- Lionel also ultimately wins them by reminding them that, even if Miles' ideas seem to make no sense in the beginning, they always turn out remunerative in the end, forcing them to admit that you should never bet against Miles. However, that is not an answer, but a way to deflect the conversation from the actual topic, which was how unsafe the fuel was. This shows early that, despite his reputation as a tech genius, Miles' only actual quality is how much money he has, and he uses them to force people to submit to him without questions.
- During Duke and Whiskey's introduction, she comes on camera for a few moments to give a quick one-liner, smiling brightly for the audience. The second she steps back off the set, she looks immediately bored and checks her phone, implying that she doesn't actually care about the subject matter. Initially this looks like foreshadowing her apparent affair with Miles, but later on in the film, she admits to "Andi" that the main reason she puts up with Duke is that she's just hoping to ride his fame to cultivate her own, as he's been giving her more screentime in his videos lately.
- The puzzle boxes. Miles sent them to his friends, who are working together to solve it, yet they are generic puzzles that don't rely on any of their strengths or expertise, and something that a stranger can (and consistently does) actually solve faster with generic knowledge. They were not designed for or by their friends, a first clue he didn't design them (the same goes later for the mystery).
- The individual puzzles are not deductive or logic puzzles, but simply a series of references the person solving it is expected to recognize. They do not test the participant's intelligence (or even testify to Miles' intelligence), but rather simply what bits of info or trivia they are familiar with (Do you know what a stereogram is? A compass? A memetic chess match? What a fugue is?), This foreshadows the mystery and the titular Glass Onion metaphor - There's no mystery, the answer is right there. Like the movie's central theme, the puzzles seem clever because of the kind of knowledge and references they employ but in reality they are very simple if you simply know what they are referencing - as shown by Duke's mom sounding utterly bored with it.
- Miles' invitation letter asks attendees to point out their dietary restrictions. This helps him improvise his murder of Duke later on, as Duke presumably told him about his pineapple allergy.
- Lionel shows the rest of his team a pile of faxes from Miles filled with seemingly inane "ideas" with no additional context. However, one of them (Child = NFT) is now a major business after Lionel and others figured out how to implement it. Miles isn't actually coming up with good ideas; it's the rest of Alpha which is actually doing the work. This also sets up that Miles' ideas are probably not his own, but things he's overheard from other people. If they were his, he'd be able to send over more detailed ideas. Instead, he's merely sending whatever stray buzzwords he comes across to his team while relying on them to assemble something coherent and useful out of them for him.
- When Andi receives one of Miles' puzzle boxes, she destroys it with a hammer. Of course, "Andi" was really Helen, who destroys Miles' house and reputation at the end of the film.
- During the puzzle box scene, Duke's mother recognizes nearly every riddle and casually reveals their answers ("It's a stereogram!") in a bored tone; she even figures out how to open the box itself before anyone else. This foreshadows both how Miles' supposed "genius" is mostly nonsense that is easy to see through, and hints at the difficulties Blanc and Helen have at solving Andi's murder: they're looking for a highly-complicated motive and opportunity planned by a brilliant mind, but the true answer is obvious and would probably easily be guessed by someone outside of Miles' inner circle. In addition, everything Duke's mother says is ignored by the others until one of the men says the same thing; apart from telling us something about the personalities of the Disruptors, this foreshadows the revelation that Miles' biggest successes came from copying Andi.
- In the same scene, the chess puzzle that the Disruptors have to solve is a Fool's Mate
, the fastest possible ending to a match and so named because it's practically impossible to win this way unless the losing player is stupid enough to set themselves up for it. Another indication that Miles is nowhere near as smart as he projects himself, and his puzzles are in fact very easily solved. - Yo-Yo Ma cameos to explain the musical puzzle in the box as a fugue, a tune which changes and forms a different composition when layered over itself. This foreshadows the film's unusual structure— the film flashes back to reveal a massive plot twist, initiating a replay of the film, the "same tune", but with the events completely reframed by the new information and point of view, and making a very different bigger picture.
- Benoit is seen playing Among Us online with friends but is quickly outed as the Impostor, due to his confusion of how the game works. Blanc joins the party himself helping an impostor in Helen, and does a much better job at keeping it secret. His Among Us character is also colored white, just like Helen-as-Andi.
- When Duke and Whiskey arrive in Greece, their motorcycle is nearly hit by Birdie's leaving vehicle. Duke stumbled onto the truth of Andi's murder because he was nearly hit by Miles' car leaving her house.
- Birdie is the first one to greet Andi aka Helen. She's similarly the first one to turn on Miles at the end and side with Helen.
- Benoit later describes himself as being "very bad at dumb things" when discussing Clue. Miles' idiotic plans and Blatant Lies are able to confound both Benoit and Helen, who were expecting a much more complicated murder mystery when investigating Andi's death.
- After Miles welcomes everyone to the island, Blanc and Andi are left alone on the beach. The first line that Andi says to Blanc is "This rich people shit is weird." This is because Helen isn't the rich CEO Cassandra Brand — she's a humble schoolteacher — and she expresses familiarity with Blanc because they already know each other.
- The captain of the yacht taking them to the island clearly does not think much of the dock Miles had made. After Duke is killed, it's revealed that no one will be able to land on the island until morning because the dock is the only place to land and it's so low that it can only be accessed by low tide.
- When describing the box he received to Miles, Benoit casually dismisses the puzzles used to unlock it as simple riddles for children.
- While we later learn that Benoit never actually had to solve them, this line sets up the idea that Miles' "genius intellect" isn't all it's cracked up to be. An actual genius found his puzzles unimpressive.
- The line also sets up the other twists of the movie: the puzzles might be not as impressive, but the way Blanc is dismissive of them is at odds with the more cordial attitude he is showing in the scene. That's because he didn't actually solve them or even see them properly, he only saw the pieces left, which included bright shapes and a Tic-Tac-Toe set, leading to his assumption. The fact that Miles doesn't contest the statement, nor seems irritated by it (which contrasts his reaction to Blanc spoiling the murder mystery) shows that not only did he not make the boxes, he didn't even bother checking them. Not only is not as clever as he paints himself to be, he doesn't even properly follow through on his own ideas, and disregards the value of others' unless he sees a way to involve himself in them.
- Moments before receiving Miles' invitation, Blanc says outright "I don't need puzzles or games ... the last thing I need is a vacation." Of course a box with children's puzzles and an invitation to a phony murder game on a private island would not interest Blanc, hinting that whatever came to his door that day was actually a real mystery to solve.
- Whilst discussing Andi's presence, Lionel says the real question is "why did Andi accept the invitation", not "why did Andi get invited". Yet throughout the movie, Blanc doesn't seem to pursue this mystery. It's because he already knows Helen's reasons for coming to the island and of Andi's death.
- Similarly, when Andi makes her entrance, Blanc is looking at the Disruptors while all of them are looking at her. Blanc knows exactly who "Andi" is and everything about why she's there; he has no reason to stare at her. He wants to see what kind of a stir her impossible reappearance has caused—and if one of the shocked Disruptors is the one who's startled because they thought they'd successfully murdered her.
- When Blanc is questioning Miles on how he could have received a box when the only ones made were specifically for the Disruptors, the question of a prototype is brought up, but Miles dismisses it and lets slip that he didn't even make the boxes himself, and later it's revealed that he didn't write his murder mystery. This hints at how he isn't actually a genius like everyone thinks, but a moron passing off the ideas of others as his own.
- Blanc asks if there's any way to reset the boxes, which Miles instantly latches on to as the explanation that he received an invitation. This is another sign that Miles can't think up anything himself, and instead relies on others for ideas. And it certainly won't be the last idea he steals from Blanc.
- The way Miles treats his murder mystery foreshadows the big twist around him.
- First, it's supposed to last three days because it's so hard. There is nothing in it, however, requiring it to actually last that long, as all the relevant clues and pieces of information have either been provided already or are in that room. Blanc himself notices that there had been more around the island, but dismisses them as unnecessary. When Miles gets huffy with Blanc for solving it so fast, he then mentions that the mystery was written by author Gillian Flynn. Not only is it a mystery he didn't write himself, he doesn't have a realistic concept of how its difficulty works, showing how his cleverness is a façade that relies on others doing the heavy lifting. The idea of clues being all around the island while they don't need to even go outside the room foreshadows the main theme of the movie.
- Then there's the way the game itself is set up: one of the Disruptors is supposed to be the murderer, yet they themselves are unaware of it or their own motivation (much like Clue, in fact, which Blanc repeatedly dismisses as a terrible game), and the island is completely devoid of other people to act as NPCs or help in providing clues or timed events (to ensure it will actually last for three days), and Miles himself actually states he will not play dead but go on with his vacation as planned. All in all, it's a set-up that requires Miles to simply throw the money at someone else and do the minimum amount of work or supervision while reaping the results and being praised for it. Not only that, but potentially having one of his friends ending up as the murderer rather than setting up NPCs to select a killer from can reflect the way he lets his friends take the fault for his actions.
- Last, but not least, Miles plays the victim role but is never in real danger, and actually set the whole thing all up, which is the exact solution of Duke's murder.
- When he announces the beginning of the game, he starts to say "As Watson said to Holmes..." before being cut off by Blanc. Most likely, the next words he was about to say were "The game is afoot", but if you know your Sherlock Holmes, then you know that it was Holmes who said that to Watson. Miles is citing a famous quote to sound smart, but he has the citation backwards.
- When Blanc asks if the winner of the murder mystery game gets a prize, such as an iPad, Miles is surprised by the suggestion, but then quickly agrees as if this was his idea all along. He later steals the idea of shooting Helen in the dark from Blanc too, based on an offhand comment the latter made about putting a loaded gun on the table and turning off the lights.
- Miles greets the visitors by playing "Blackbird" on the very guitar used to write it, which he then chucks aside, likely causing significant damage to a valuable collector's item. The same reckless disregard applies to The Mona Lisa, which is destroyed due to his disdain for proper safety.
- Miles also misplays a chord on "Blackbird" when the yacht is arriving, despite having isolation and free time to practice. Later, he states that the murder mystery scenario for his party was written by Gillian Flynn. Throughout the film, we learn Miles is very good at paying other people to create complex and awesome things, but when he's left to do things himself, he falls a little short.
- Duke, before being given the anti-viral spray by Miles' assistant, asks if the spray has any pineapple in it because he "doesn't dance with pineapple". As it turns out, Duke is deathly allergic to pineapples. Miles later pours pineapple juice into Duke's drink, with fatal results.
- Several of the Disruptors note that Andi's behavior seems off. She's actually Andi's sister, Helen, trying to mimic her sister's standoffish behavior.
- The Disruptors seem friendly at first, but they all turned their backs on Andi and betrayed her once it became clear that they'd be better off supporting Miles. After Helen destroys Miles' reputation, the Disruptors all turn their back on Miles.
- After showing off his record channel numbers to Miles and netting a job at Alpha News, Duke refuses to show them to Birdie. This is especially strange, considering that she was the only other Disruptor he actually liked and who actually liked him, seeing by their hug upon reuniting at the pier. Furthermore, Duke's channel getting a huge increase in numbers at that exact moment feels rather sudden and random considering that he hasn't been streaming on the island, and hasn't mentioned any particular video that he's released that he's expecting to go viral. This is because he was lying about his channel numbers causing the alerts to go off; they were actually caused by the news of Andi's death breaking to the public, Duke had put two-and-two together to realize that Miles must be responsible for it, and he was showing Miles—and only Miles—the article on Andi’s death because he needed to keep it secret from the others to blackmail him with it.
- As Duke dies, he grabs onto Miles' shoulder. Looking back, it was possibly an attempt to attack Miles or leave a Dying Clue that Miles was the killer due to him being unable to speak.
- After Miles reveals that Duke drank from his glass, he cowers behind Blanc, accuses the surviving Disruptors and Peg of attempting to kill him, and declares that he will keep all of them in his sight. Yet when the lights go off and Whiskey declares that Andi's the killer, he runs off on his own when he could have been easily picked off by Andi. That was because he wasn't the one who had to worry about the killer, she was.
- On a similar note, despite having apparently been scared of others and cowering behind Blanc, then freaking out when the lights go out, after everyone hears the gunshot and is calling out to each other, Miles is one of the people who, after a moment, reveals his presence. If he was really concerned about someone trying to kill him, a gunshot should have freaked him out even more and made him want to stay far away from the group. But because he's the real killer and doesn't have any reason to fear harm from any of the others, he identifies himself as an attempt to have an alibi for where he was during the shooting; he didn't speak up as soon as the others did because it took him a minute to get back there after shooting at Helen.
- Furthermore, with Duke's murder, Miles frames the incident as someone trying to kill him—after Blanc warned him of this possibility. It's an early sign that he can only steal ideas suggested to him, later followed up by the blackout and burning the napkin being actions prompted by others suggesting them.
- Miles backs away from Peg as she approaches, seemingly out of fear she's the killer. He was actually preventing her from noticing he has Duke's phone and gun.
- While all the Disruptors are surprised that Andi accepted her invitation, when Miles sees her he looks like he's seen a ghost because he thought that he'd killed her.
- Miles interprets Disruption Theory as breaking something small, which others will celebrate, then escalating to larger and larger things despite increasing pushback, before finally breaking something nobody wants to be broken. After Miles burns the napkin, Helen does almost exactly this, breaking increasingly large pieces of art, then burning down the Glass Onion, and then destroying the Mona Lisa. It also foreshadows the so-called "Disruptors'" reaction to it: after their initial shock when Helen starts breaking the statues, they begin cheering her on and even join in on breaking some themselves. But once she starts smashing bigger things like the piano and then starts the bonfire, they just get increasingly uncomfortable and even urge her to stop, and then try to physically hold her back as she keeps going, demonstrating that, for all of Miles' boasting about himself and his friends being "Disruptors", they don't really live up to the name when the chips are down.
- When Miles reveals that he has the Mona Lisa in his house, the second thing he reveals is that he added a button (concealed in a very goofy-looking figurine in the middle of the room) to make the armored glass cover protecting it slide away. The cover slides into and out of position repeatedly throughout the following conversation, and it even gets several close-ups. You just know that somehow that is going to bite Miles in the ass, long before Helen decides to get her revenge by setting it ablaze.
- In the past, Birdie made a tweet containing an obvious slur for Jewish people (it had the word "Jew" in it), not even knowing the connotation and thinking it meant "cheap". We find out a similar, but much worse thing happened with the later reveal that she approved the usage of a sweatshop in Bangladesh, thinking "sweatshop" meant "place where they make sweat pants".
- During the leadup to the murder mystery game, Birdie asks if the players can team up, and Miles says no. Blanc solves the case by teaming up with Helen.
- Miles describes the beauty of the Mona Lisa as the illusion that the painting changes every time you see her; her smile subtly changes each time. It's a fitting metaphor for how everything in the movie is recontextualized when seen a second time.
- Blanc learns that Andi recently sent an email threatening to "burn down" Miles' empire of lies. Helen ends up making good on the threat in a more literal way than Andi probably intended.
- During Blanc and Helen's meeting the night before going to the island to discuss potential motives and opportunities for the Disruptors to murder Andi, Helen brings up the possibility that Miles himself was the killer. Blanc dismisses this because Miles "is not an idiot", and wouldn't risk being a suspect for the death of Andi so soon after a very public trial where she sued him, especially if it came out that she sent an email showing the proof that would support her side. And yet, sure enough, THAT'S EXACTLY WHAT HAPPENED. Because Miles IS an idiot.
- While making Knives Out, Rian Johnson learned that Apple does not permit film villains to own or use iPhones onscreen, so he had to have the culprit use an Android. Watching this film closely reveals who the murderer is well in advance, as all the Disruptors use iPhones except Miles, who doesn't own a phone. Additionally, he is never seen holding the iPad he gives to Blanc, throwing it to him from off-screen.
- As mentioned on his character page, Duke isn't well regarded amongst the Disruptors. This is the first sign that none of the Disruptors are really friends (at least anymore) and are brought together by something else (Miles' money and influence).
- The cuckolding scene foreshadows the murderer, victim and murder method. It turns out Miles was making a habit of slipping things into Duke's Whiskey.
- Lionel is notably unsettled when Miles brings up his plan for Klear, and Claire immediately panics for a moment when he throws the sample to Blanc. Which is a natural reaction, considering the two of them know that Klear is a highly volatile substance. Wouldn't you be alarmed if you saw someone throw a highly flammable material around in a room with several things that can set it off, such as Miles' own blowtorch?
- Andi blows up at the other Disruptors, saying that "her life" was taken from her because of one of them. She's not being metaphorical; her whole outburst is effectively spelling out that she knows one of the Disruptors killed the sister she's pretending to be.
- A small one for fans of modern art: the Matisse in Miles' bathroom is Icarus, setting up the pretender's eventual fall.
- Andi spends the first half of the film being cold, resentful, and removed from the group, with her character both the least colored-in and the most suspicious, leaving her as the biggest mystery in Miles' party. This is not because she's a killer, but because Andi is quite literally the mystery at hand—she is the murder victim Blanc is investigating, and the Andi we've watched is her timid surviving twin Helen trying to maintain cover impersonating her and taking opportunities to sneak away and snoop while she and Blanc investigate the crime.
- A signature trick of foreshadowing in this film is how multiple key movements and details of the mystery are dropped in plain sight, with only camera framing or distractions keeping them from being caught by the average invested viewer.
- Closely watching the shot of Birdie at the pool before Andi is revealed when Birdie takes off her hat and uncovers the frame shows an object being dropped from above into Birdie's swim bag right beside her—this was Helen dropping in the recording device before sitting down.
- The film shows Miles and Duke sitting down and Miles placing Duke's drink into his hand, which will later be proven as the way Miles pushed a tampered drink onto Duke. The film tries to make the viewer doubt by providing an explanation where the visual depiction changes to show Duke picking up the glass mistakenly from the table, but viewers paying attention to the guys the first time, and not to Birdie twirling in her dress like Miles asked everyone to watch, will see that the second version of events is inconsistent and a lie.
- Some shots in the film show Miles with Duke's phone, and Miles with the gun and then stashing it away in an ice bucket, but the framing and action is designed to keep those out of notice.
- After the blackout, Blanc runs up to Andi and openly calls her "Helen", the meaning of which is imminently revealed upon the approaching plot-twist replay. In the chaos of the scene, this detail is very easy to miss.
- When Peg goes to Miles and outright begs him not to have Birdie make the statement revealing she stupidly, unknowingly allowed the use of a sweatshop in one of her ventures because that would not only ruin Birdie but Peg herself, due to most of her resume being working for Birdie, Miles gives her the brush off and a smile as he asks her to get Birdie to make the statement. This foreshadows two big indicators of Miles: 1) he doesn't give a damn about anyone but himself, not even to offer Peg words of encouragement (such as, "Birdie told me how much you help her and do for her. You'll bounce back after this is all over") and 2: he adamantly believes his natural charisma (which he does have, despite being an idiot) is more enough to get people to agree to whatever he asks of them.
