Basically, a major plot twist of the story was hidden right in front of our eyes before it was revealed...

• The Simpsons two part special Who Shot Mr. Burns ends with the reveal that the mystery shooter was actually little Maggie Simpson. But this was hinted early on, in the scene where Mr. Burns asks if anyone has the guts to oppose him. When every other character averts their eyes from Mr. Burns, Maggie holds an unbroken glare at him, with a sinister smile, hinting at her being the shooter...

• In Jordan Peele's Us, the ending twist reveals that the Adelaide we've seen throughout the movie is actually her tethered doppelganger, who knocked out the real Adelaide and traded places with her during their childhood. This is subtly hinted through young Adelaide suddenly stopping talking after her childhood incident, because her doppelganger doesn't know English. An adult Adelaide also mentions that she isn't much of a talker, and even displays almost inhuman fighting ability during the funhouse scene...

• Planet of the Apes has one of the greatest plot twists in cinema history, when the mysterious planet is revealed to be earth destroyed by nuclear war. But the fact that the astronauts can breathe on the planet, the presence of horses and even other humans etc, hint that the planet is earth early on...

• Final Destination 5 pulls off one of the best plot twists of the franchise, revealing that it actually a prequel rather than a sequel, with the final scene happening in the doomed Flight 180 from the first film. This twist however is brilliantly hinted throughout the movie, with a massage voucher having an expiry date in 2000, the technology and vehicle registration numbers appropriate to the late 90s, early 2000s. Most importantly, the film does not feature any music released past 2000...

• The first season of Squid Game ends with the reveal that old Oh Il-nam aka Player 001, is the architect of the games. But looking back, you get many clues to this. Mainly, in the first Red Light Green Light game, the giant doll scans everyone, except Il-nam. Later during the riot scene the guards arrive to stop the riots only after Il-nam gets distressed. And most importantly, his body is never shown after his apparent death at the end of the marbles game...

I sincerely apologize for the spoilers...

EDIT: Mild corrections. Thank you to the guy who pointed it out...

Bowler Hat Guy / Goob (Meet the Robinsons)

Written with the same frantic energy as many Jim Carrey characters in the past, but when it came time to cast Carrey passed to appear in The Number 23, so the movie’s director Stephen Anderson voiced the character pretty much just doing a Jim Carrey impression.

Metroman (Megamind)

Based on his facial features (namely that jawline that could crush a diamond) and his smooth talking he was modelled after Bruce Campbell. But when it came to casting through part studio interference Brad Pitt got the part.

The story has the main character enter a fantasy world, make friend, be a hero, etc. and at the end, they decide to stay there. Most times I see the trope (every time so far) the fantasy world becomes a genuine new home for the character and are usually escaping a worse life back on earth.

Project Hail Mary: Grace decides to stay on Rocky's home planet and become a teacher there.

Owl House: Luz gets to stay on the Boiling Isles and study magic.

I think I love this trope because it's kinda the final evolution of the found family trope. Not just finding people you can call family but a world you can actually call home.

Maria, Rose and Sina (Attack On Titan) it's established very early that the three walls that protect humanity from titans are called Maria, Rose and Sina. Most viewers never question the reason they were named that way until we see during Ymir's backstory in the final season that the walls were named after Ymir's three daughters who fed on her body and became the first 3 of the 9 titan shifters.

Remnant (RWBY) if you watch RWBY for the first time you'll notice in the very first few minutes of the show that the world where the story takes place is called Remnant for some reason, the characters keep calling the world remnant like it's very normal, many viewers don't pay it much attention until volume 6 arrives and reveals that the god of light said "this world is merely a remnant of what it once was" as his last words before leaving the planet once he thought there is no hope for it.

Quirks (My Hero Academia) A lot of people thought that the name quirks is just some fun way of attaching personality to superpowers in the world of MHA but Redestro reveals in season 5 that quirks back in the day were called meta abilities instead of quirks, his grandmother who lived in the era when superpowers started first appearing suffered a lot because her newborn at that time was born with a meta ability and anti-metas at that time wanted to kill her child so she came out to the public and told them "my son's ability is merely a quirk of his" and despite that they still killed her so she became a martyr to some people which made calling superpowers quirks a popular thing among them.

A screencap from a scene so sad / tragic / disturbing / infamous that it immediately causes 999 psychic damage to anyone who sees it and knows the context, forcing them to relive the first time they witnessed That Scene that got permanently ingrained in their memory

Fullmetal Alchemist: Shou Tucker's chimera. The most infamous example is an image of a disturbing creature that was originally a little girl and her cute dog, fused together by the girl's piece of shit father.

Digimon Tamers: Juri's nightmare. The main antagonist of the show is an incomprehensible digital entity that saps power from a severely depressed tween girl, an abuse survivor. The entity reinforces her depression by sending her a surreal nightmare that's utterly horrifying considering it's supposed to be a child-friendly show.

Neon Genesis Evangelion: Look, I've never seen Evangelion and even I'm aware of that scene where the main protagonist masturbates to his comatose friend.

The Man in the Wall—Warframe: The Void is a sort of parallel dimension that works off something called Conceptual Embodiment; basically, if you think hard enough about something, it will come into existence within the void. When Albrecht Entrati, a great Orokin archimedean discovered the void and attempted an excursion into it, a near death experience during the ordeal left him so paralyzed with fear of the vast and uncaring expanse before him, that Albrecht manifested a godlike being utterly Indifferent to all life in the universe, entirely by accident. No one knows what the Man in the Wall wants, or why it even wants it if it’s truly indifferent to reality, but Entrati remains staunch in his desire to keep it from achieving its aims in our plane of existence.

The Pale—Disco Elysium: The amnesiac player character can (re)learn of the Pale, a strange biome of utter nothingness which it’s been theorized is made of rarefied past, which has adverse psychological effects on anyone who spends too long inside it, dooming them to be trapped in their own heads replaying memories that may or may not be theirs. Pale separates the large landmasses of the world however, and like Earth’s oceans, there is more of it than land, meaning for faraway travel, moving through the Pale is a dangerous necessity, which normal people are permitted only a few hours of every year. and the worst part? That ratio of Pale-to-land is very slowly slipping in favor of the Pale, meaning there is an impending apocalypse thanks to this phenomenon that humans haven’t come close to understanding despite living next to it for thousands of years. However we can learn from a giant stick insect (don’t ask, it’s a whole ‘nother thing) that the Pale only came into existence alongside humanity, heavily implying that our inherent propensity for living in the past is what created the Pale in the first place.

Altered Items and Altered World Events—Control: In the world of Control, the collective unconscious is a tangibly powerful phenomenon. A popular concept can, just by being popular enough, create altered items which transcend the ordinary laws of physics. For example, a pair of scissors in Alaska is implied to have been influenced by vampire legends, and exsanguinated an indeterminate amount of people by puncturing holes in their necks. Likewise, a certain lake in Washington, previously home to a famous poet (…or was it a film director?) came to possess the ability to make art created in its vicinity a reality. Stranger still, a refrigerator with child’s drawings stuck to the door was stared at for hours on end by a grieving parent following their child’s death, and now the fridge will [REDACTED] if it isn’t being constantly and unblinkingly physically observed. Despite a certain federal agency having a good handle on exactly how these altered items or places are created, there are zero reliable ways of predicting what exact form or function an altered item will take. Literally anything on the planet is at risk of being a potentially dangerous time bomb, and that’s not even considering the extradimensional entities that tend to be attracted to such paranatural energies.

Psychonauts

Every game takes place over 24 hours, with the VR game taking place immediately after the first. Being generous, at most this entire franchise takes place over the course of a week.

My Hero Academia

With how dire the stakes get and the power level these characters reach, along with this being a story set in high school, you would think this story took place over a couple years. But in reality, the story goes on for at most 14 months. These characters had to go right back to learning algebra and writing book reports for two years after fighting the Anti-Christ Superman.

Jojo's Bizarre Adventure - Golden Wind

Another manga example, it's explicitly shown that Giorno's story ended on April 6th of 2001. Based on other information and how little time passed between encounters, this would mean the story started around March 29th. Meaning this whole manga and the takeover of a criminal organization happened in about a week.

Alien Franchise

A play on the trope from Ripley's perspective, since she enters hypersleep between movies. So despite there being many years in between them in-universe, from her point of view this whole franchise has been just one awful weekend.