It's pointed out subtly several times in the game that Greenvale has a lot of stuff in it (art gallery, big fancy hotel, sawmill, two bars...) despite being a relatively quiet small town. This is foreshadowing that Greenvale used to have a larger population that was killed off by Kasen's experiment.
York's invisible friend Zach is actually you, the player.
Quite the observation. Wouldn't you agree, York?
When York opens a door he quickly looks around before going in. Why? To look for any threats before actually going in. Looks like he has been jumped before.
Becomes even more brilliant when you see the flashback to when Kaysen attacked Zach's family. Zach was watching from a doorway where he couldn't immediately see Kaysen, so York's cautiousness is a defense mechanism for his trauma as well.
Not only that, but York's signature mannerism of putting two fingers to his temple while saying "Don't you agree, Zach?" is him mimicing his father's last words and actions before shooting himself in the head.
Kaysen's final form makes sense: He doesn't need to look like a monster to be a monster.
During the autopsy scene, when York finds out that Emily was watching a movie on TV the night of the murder, he grinds his investigative questioning to a halt to ask her what it was and then rattle off the year and director before moving on. Seems like just another case of Yorkbeing York, until you poke around Emily's house and car and realize something about her: She's just as huge a film buff as he is. This seemingly-innocuous moment is probably when she starts to fall for him, because she realizes that they actually have something in common.
During one of the car chats in Episode 3, York is trying to work out what his feelings for Emily are. He tells Zach that she reminds him of "something he used to feel"—the feeling of wanting to protect someone, but at the same time, feeling protected by them. He wonders out loud: "Who used to make me feel that way...?" It's Zach himself. York is Zach's protector, but at the same time, Zach still helps guide him and keep him anchored in the real world.
It could also refer to his guilt toward his mother's death, and point to a desire to protect Emily to make up for how he believes he failed his mom.
During the section where you play as Emily why can you suddenly run indefinitely without the meter filling up and forcing you to stop? It's because Emily isn't a smoker like York.
At the end of Quint and Becky's sidequest, York says "another young life saved Zach, good job". Remember that in reality, York is an alternate persona and all utterances of York and Zach reversed; so the line is actually "Another young life saved York, good job", delivered by Zach, the true persona. Who was the previous young life that York saved? Zach himself.
When you are at the final battle, Zach ends up running DOWN a whole flight of circular stairs away from Kaysen, only to end up at the TOP of the roof of the clock tower... huh?
Well, given that Kaysen is implied to be an Eldritch Abomination, and he might very well be warping space-time, combined with the whole Through the Eyes of Madness thing in the dark world, there's at least two reasons why this might have happened.
In Spy Fiction, Kaysen is killed by Lauder. This never made any sense to me, because he was still alive back when the gas was released meaning he was super paranormal for a while. If that's the case, how did the Lauder kill him. If the Lauder did kill him, either the events of Greenvale shouldn't happen, or Spy Fiction took place after DP and never happen because Zach killed Kaysen.
This is because Kaysen is part of SWERY 65's Reused Character Design group. Deadly Premonition and Spy Fiction are not canon to one another. The same thing goes for General too, who was eaten by Pirhannas.
During the second victims death York just stands there watching her die. Alright he made a mistake assuming she was dead the first time I can forgive that (although he does the same damn thing for the third victim too) but after seeing she was alive and after the trap had been sprung he didn't think, maybe he should attempt to support her weight to stop her strangling to death two feet in front of him. Don't say it was an instant death either, we clearly see her still alive even before York starts seeing things from behold the grave.
By the time the trap is sprung, it's too late...It's not INSTANT, but, like with 'Power Rangers' transformations and such, it's quicker then it looks.
Given the method we see for creating red tree saplings, does that mean there's someone buried in a shallow grave under George's lawn?
That's just the methods to get the seeds to sprout. After becoming saplings, they can be planted like regular trees.
Although that's not the only fridge horror at George's house. Remember his mother's corpse in the basement? Kaysen most likely raped her. Is that why George become so fanatic about the red trees?
More Fridge Horror comes in when you consider the possibility that it wasn'tKaysen who raped his mother... Guess he might have gotten back at her for all of those beatings...
If you check the Galaxy of Terror late at night, sometimes you can see Thomas or Carol head to a room you can't enter. If you check the map you'll notice they're with someone else George, and later you find out that it's the secret BDSM room. With the way the game treats Thomas as a fellow victim despite his antagonism and death at your hands, and his comments on George's cruelty, you realize that meek and gentle Shrinking Violet who cooks lunch for you daily is a Love Martyr who was probably being sexually and physically abused right under your nose the whole time, and it's implied his eventual psychosis is partly the result of Break the Cutie.
Likewise, Carol's abrasiveness may also be the result of similar abuse.
Pay close attention to Brian Xander Morgan's gun, it's a magnum, now take note the prize in Willie's Doghouse after completing his sidequest with all seven bones, a magnum. Kaysen likely stole that Magnum from Xander's dead body.