In the first levels of Mafia Town, Hat Kid can play patty-cake with certain Mafia goons, only to get punched in the face during said activity. Not only does it show the Mafias' willingness to hurt children, it perfectly foreshadows future interactions of Hat Kid's with other notable characters: she and Mustache Girl team up to take on the Mafia, only to fall apart when the two disagree on how the Time Pieces should be used; she and the bird movie directors have fun making the movies, only to have the winner betray Hat Kid when he wants to use the Time Piece for his own purposes; she comes to work for the Snatcher, only to have him turn on her after all the tasks are completed.
Alternatively, considering the Mafia's... questionable behavior, it is likely that ending a game of patty-cake with a sucker punch is just how the Mafia play that game normally. To them it's normal, but Hat Kid thinks otherwise and thus is unable to catch on.
However, considering there's that one Mafia who willingly punched a child, there's a good chance that most of them just see no problem with it.
Battle of the Birds
Right from the start, the Owls on the Owl Express are visibly confused about the Conductor's movie-making, as they expected to be normal train passengers and somehow got shanghaied into his movies. This seems like just a comedic detail, but put it together with the Conductor's complaints about how bad his actors are, and the true genius shines through: his actors are bad at actual acting, so he lets them believe they're normal passengers so their "acting" will be genuine. It's the logical extreme of Enforced Method Acting!
Up to the Award Ceremony, the Conductor has been almost nothing but a complete greedy Jerkass to everyone through and through, and yet won all the awards except one. Meanwhile, DJ Grooves has been the Nice Guy that, besides having grateful staff even in the past, got Hat Kid clearance into Dead Bird Studio and does away with her debt. Once they win and keep a Time Piece for themselves, however, they begin to represent the theatrical tropes of an Obvious Villain and a Twist Villain, respectively.
The boss fight in the finale, and how it makes sense despite Static Role, Exchangeable Character being in effect. The use of knives in DJ Grooves' version doesn't seem to make sense at first, unless you picked "Auntie" in "Murder on the Owl Express"; he was part of that movie the whole time. (Or, alternatively, unless you remember that one of his endorsements in "Picture Perfect" involved a cooking show!) The use of a disco ball makes less sense in The Conductor's version, but he is adept at making death traps. Finally, the photos make sense regardless of the version; they could be either evidence photos from The Conductor's mission or paparazzi photos from DJ Grooves' mission.
It being easier to end up with DJ Grooves as the boss, as opposed to the Conductor, due to the former having missions that are far easier to get high scores on. It makes sense when you realize that the nice if eccentric mentor guy being the villain, and the loudmouthed Jerkass showing up to help you stop them, is an interesting plot twist that wouldn't be out of place in a Hollywood movie — like these guys are making!
It almost even seems like this is meant to be the canonical outcome: The Conductor's version of the fight gives him DJ Grooves' hitbox rather than his own, the phone call alerting you to check the basement is directly referencing Murder on the Owl Express complete with the same was-previously-implied-to-be-the-Conductor voice, the heart-to-heart moment is far more in-character for Grooves, and the attacks that reference past missions are almost entirely from Grooves' missions (photos, disco balls, the band) - with only the time bomb and knives being from the Conductor's, with Grooves explicitly mentioning he stole the former and the latter being justified above.
It makes sense either way since the basement is storage for props from both studios so either director could have just grabbed anything they needed, the pictures are justified above and the voice modifier is likely in the Conductor's possession while DJ Grooves (obviously being a DJ) likely has knowledge of audio editing. Also in terms of the attacks it's 3 from each director: the buzz saws and bomb being from Train Rush and the knife being from Murder on the Owl Express, the disco ball and owl band are from the Big Parade and the cars being from Picture Perfect (Grooves says he stole the bomb in his version of the fight, and the owls could just be Express Owls the Conductor enlisted to help him). In terms of being in character, the heart to heart is indeed more in line with the amicable Grooves, and so is him saving Hat Kid. The Conductor claiming the competition was rigged, using the heart to heart to pull a nasty trick, as well as him trying to cheat to satisfy his perfectionism fit him better than Grooves, so both ways work out in that fashion. Finally in terms of points, while it's easier to gain points in Grooves' levels, the Conductor's levels have more ways to gain points (the case files and time bonuses in the first and second levels respectively).
In terms of the idea of the twist fitting in with films the directors are making makes sense with both directors. The Jerkass being the villain and the Nice Guy saving the hero (both of which are boring and predictable tropes) makes sense with the Conductor who's shown to be running out of ideas at this point. The "evil eccentric mentor and jerk ally" idea listed above makes sense with Grooves since he seems more creative than the Conductor.
You remember how, in the Dead Bird Studio Time Rift, the Conductor and DJ Grooves were friendly before they actually got into the showmaking business? Well, it turns out that they still have a wee bit of their friendship left, all things considered; neither one of them knew how the Time Pieces worked before the very end of the chapter, meaning someone had to tip them off after the awards ceremony. And since directing a movie involves knowing how to act, for the sake of telling if one of their actors was phoning it in — especially since both complain about the lack of ability their respective actors possessed to Hat Kid — it allows them to better hide aspects of their character they don't want anyone seeing, like the Conductor's hidden heart of gold or DJ Grooves' dark side. When you put it all together, the call about the awards ceremony being rigged takes on a whole different tone: for all the rivalry they have going on, they value their friendship just a bit more, and the loser knew Mustache Girl was bad news from the start and called Hat Kid to thwart their friend's budding power addiction.
During the boss fight, the bomb that gets stuck to Hat Kid starts counting down much slower once it reaches 10. Of course it does, because the counter's a movie prop that's built to invoke Magic Countdown for drama, it's just attached to an actual bomb.
To get the "Why" achievement you must type something immature or crass on Spaceship's computer or answer the Crows' questions with any inappropriate or swear word. You can also unlock this achievement by typing the word "PECK", because of course it counts as a in-universe swear word by bird standards.
In "Murder on the Owl Express", the Conductor is extremely eager to play along if Hat Kid decides to declare herself the murderer. Of course he is... a Tomato in the Mirror twist where the main protagonist is the actual villain would add so much more depth to his latest movie.
In Hat Kid's spaceship, there's a mail room filled with an endless stream of letters and packages, which goes unexplained. However, since you can only access the room after getting the Ice Hat with yarn first available in Battle of the Birds, you will not be able to enter the mail room until you've become a movie star. Thus, its purpose is clear: all of that is her fan mail!
Subcon Woods
The Snatcher's obsession with contracts becomes more than just a Deal with the Devil gag once you enter Vanessa's Manor, and find the diary entry mentioning that the Prince was a law student.
Why does the Snatcher seem so obsessed with capturing people and forcing them to do his bidding? He used to be a prince, and he was denied becoming king when Vanessa went insane; his kingdom turned into the Subcon Woods and he became a shadow being. It's probably a twisted royal mentality of making people "serve" him, which is especially upsetting as he was, from what little we see, a good man before the tragedy.
In fact, the Snatcher seems to know a lot about contract law, and he dabbles in chemistry, too. Did he go to university or somethi— …ah.
Why are you not allowed to use your hats in Queen Vanessa's Manor, despite the fact that they all would be incredibly useful to complete the job? Well, since it's implied that the Snatcher used to be the prince, he may still have some subconscious love left in his heart for Queen Vanessa, despite everything she's done to him, and wouldn't want Hat Kid to hurt his beloved. The Sprint Hat and Time Stop Hat, however, would be useful for running away from Vanessa. The Snatcher forbidding those hats would be him simply being a dick and making your job harder for laughs. The one hat you are allowed to use, the Dweller's Mask, can't hurt enemies and isn't that useful in the Manor anyways, the hidden loot at the end notwithstanding.
The Dweller's Mask being an exception to the contract makes even more sense following the first DLC, in which a storybook reveals that the Dwellers are child ghosts who didn't sign contracts to become the Snatcher's minions. He has no power over the Dwellers — or their masks.
The greater reason for hats being disabled, however, is probably just to preserve the mood. Some of the wacky abilities could disrupt the tense horror tone, and things like Vanessa's voice being turned into grumbles with the Mumble Badge would lighten the tone as well. The Dweller Mask doesn't have anything about it to make things less scary, and instead is used for optional flavor to reveal more scary things. After all, the gameplay doesn't really need hat abilities, but the tone rather requires that you not have them.
It may seem odd at first that the ice around Subcon Forest can only be broken by the Dweller-infused cherry bombs, but not the bombs from the Brewing Hat. Until you realize that the origin of the ice is from Queen Vanessa, which is probably imbued with some special magic that prevents the ice from melting or breaking by normal means. The Dwellers are spirits that used to be the children Vanessa visited before the tragedy, so logically, it makes sense that they're the only ones with the ability to break Vanessa's ice.
It’s clear that the Snatcher hates Hat Kid to the point that he wants to see her die, so why doesn’t he take the opportunity to do so when he came aboard her ship in person? Because that last contract Hat Kid altered back in Subcon really was binding (he signed and stamped it before Hat Kid altered the terms and signed it herself): as much as he hates it, he’s contractually obligated to be her best friend forever by his own powers, and best friends don’t hurt each other. However, it seems he may have found a way to Loophole Abuse his way around this: challenging her to beat his many Death Wish contracts to watch her die over and over again isn’t hurting her directly, it’s just a ‘friend’ challenging her to a ‘friendly’ game.
Why does the Dweller Mask reveal hidden writing and objects? Well, it's spooky, right? But why is it tied to the Dwellers? Well, the Dwellers are the only entities in Subcon Forest who witnessed what happened to it without being corrupted. Maybe the things you can see are things that used to be there, or things they are trying to tell you about what they saw. Maybe the things their power reveals are attempts to make their story known or possibly bring about change. The silhouette in Vanessa's basement, for one, could be there because the ghosts want you to know what happened, and maybe the writing on the walls wasn't made by the Queen, but the other spirits in order to warn or inform.
The “Subcon” in “Subcon Woods” probably stands for Subcontract. Why it would be named that is obvious with the Snatcher’s love of contracts.
It could also stand for “Subconscious”, with all the spooky ghosts and whatnot.
Notably, the entrance to Subcon Forest is located in Hat Kid's bedroom. So it's "subconscious" as in dreams.
Snatcher is throwing potions at you in his boss fight because he has your Brewer's Hat.
When the Snatcher steals Hat Kid's hat, he wears it in the exact same position as his old crown from his days as a prince.
Time's End
Considering how Mustache Girl was judging everyone, it makes sense why her castle is so dangerous. If they die on the way to her and are already bad guys, no skin off her nose if she doesn't do it herself.
Nyakuza Metro
Despite the money in the Metro apparently being currency, it's never added to your Pon counter. Beyond Hat Kid's diary revealing that she has no clue what the paper money is and using it to elevate the telescope, there's another reason: the backroom reveals that the Empress is making Counterfeit Cash off of a printing press, and that's why they're never added to your Pons.
A vague bit of Trivia that only anime fans are likely to know is that the Japanese equivalent of "Meow" is "Nyaa". The title of this chapter said aloud is Nyaa-kuza.
In western superstition, it's bad luck for a black cat to cross your path. It is therefore fitting that every last Nyakuza feline has spotless black fur, you will have dozens at minimum do so as you play through the Metro, and literally hundreds to thousands of them "cross your path" during the finale.
Rumbi's Time Rift storybook reveals just how hard the loss of Hat Kid's soul was on her. But it indirectly explains something else about that ordeal, too. When she gets it back, it's stated that she feels the usual amount of empty again. Why would she normally feel partly empty? What could have hurt her that badly? According to Rumbi's storybook, we saw it happen: her betrayal by Mustache Girl. For one brief, shining moment, she wasn't alone.
Arctic Cruise
With all her mischievous nature, Hat Kid sinking the SS. Literally Cannot Sink in the end of this chapter just to get her hands on a Time Piece seems uncharacteristically callous for her, to the point many a player have complained about it being Out of Character. However, that's only the case if you assume she actually was trying to sink the ship. Once you remember that she is actually a licensed Space Craft Pilot, her actions make a lot more sense; she was probably overconfident in her piloting skills, assumed steering a ship couldn't be too different from steering a spacecraft, and had no idea how icebergs work and how treacherous they can be for ships — she wasn't trying to sink the ship, she was trying to dock onto the iceberg!
Alternatively, as a spacecraft pilot, she may be used to maneuvering in 3D instead of 2D. She may very well have been planning to just pull up and go over the iceberg, only to realise that boats can't do that.
General
Purple Time Rifts are formed from the memories of beings that were hit in the head with Time Pieces, with each Purple Rift usually themed solely around about the level it's found in. The only Purple Rift that seems to lack this cohesive theming is Tour, which instead goes for the All the Worlds Are a Stage route. Considering that the Tour is found on Hat Kid's ship and it's only able to be accessed after beating the game, Tour is probably meant to be Hat Kid's memories of her adventure.
"Rumbi Factory" in Nyakuza Metro also seems to lack this theme, as the Rumbis have otherwise nothing to do with the Empress or any of the metro cats. Except... it kind of does. A few locations in the metro have cat-themed vacuums (most notably Green Clean Station) that act like Rumbis. Thus, the factory rift makes perfect sense: It's memories from the Empress stealing the blueprints of the Rumbis and tweaking their design to use in her metro. Hat Kid's Rumbi was presumably bought or gifted to her before the factory shut down, and Hat Kid herself built it, so hers works as intended.
Fridge Horror kicks in when you take into account the malfunctioning exploding Rumbis, and the factory closing down. Want to bet it was the Empress sabotaging the other Rumbis so no one else could have them, and to take out people she didn't like?
One of the rooms in Queen Vanessa's Manor is clearly a nursery, with a crib, rocking horse, and toys around. Were the royal couple planning to have children? As horrifying as their fates turned out to be, it might have been worse if a baby was involved...
In Mustache Girl's storybook, she is shown to have a family who are never seen in game. Considering how the Mafia took over her island, it isn't hard to realize what most likely happened to them...
In the game's intro, when the Mafia smashes open the door to Hat Kid's ship, the contents of the ship get sucked out into space as one would expect for a ship vented to hard vacuum. Yet in the game's ending sequence, Hat Kid somehow slams the exact same door wide open with no vacuum effects at all.
Maybe Hat Kid learned from the intro and got the Time Pieces sealed more tightly. Another question is how the heck did the Mafia even reach her in space when they're stuck on the island in the first place?
Maybe the race wasn't Mafia's first attempt with rockets...
Just before the Mafia goon smashes through the glass door, he attempts to open it up, before Hat Kid stops him. During that time, no vacuum occurs. Perhaps a vacuum only occurs if the door is opened improperly (or smashed open), but does nothing if opened normally. Maybe just chalk it up to Hat Kid's unusual ship design (which is apparently has its glass being meteor-proof, but weak against fists).
In Nyakuza Metro, when Hat Kid steals all of her Time Pieces back and gets caught by the Empress, why doesn’t she end her right there? We’ve seen before that she’s not afraid to get her claws dirty when she killed one of her Underlings on suspicion of stealing, and having Hat Kid cornered right in front of her would’ve been an easy kill for her. But instead, she places a bounty over the Metro and lets her get away to start a chase.
I think there may be a few factors why the Empress decides to make a spectacle of it all instead of just killing Hat Kid outright. The underling the Empress killed earlier may have just been a low-level (and replaceable) minion, whose only crime was merely being suspected of trying to steal her jewelry. Hat Kid, on the other hand, was, up until that point, the Empress' most loyal and dependable underling (with even a possibility of becoming something of a protege to the Empress), and she was caught red-handed stealing back the Time Pieces. Also, with the Empress calling the bounty on Hat Kid's head instead of just killing her, it shows just how powerful and influential she is when she gets the the whole metro going against Hat Kid, to make the girl truly regret betraying the Empress and fearing for her life.
In the base game, when Mustache Girl breaks a time piece, time reverts to a few moments before the time piece was broken. Similarly, after the final boss, Hat Kid is seen breaking the ball of time pieces she collects to undo Mustache Girl's world domination plot. However, in the Seal the Deal DLC, the crew of the Literally Can't Sink accidentally break a time piece without turning back time, and Time Piece shards also appear in the Nyakuza Metro DLC. Why didn't they turn back time? How, exactly, do Time Pieces work?
The seals are just that incompetent that they couldn’t make the time piece do what it’s supposed to.
Like you said, Mustache Girl broke the Time Piece and time turned back a couple seconds before. It's possible that when the Seals broke their Time Piece that the rewind backwards was subtle enough for no one to really notice, especially Hat Kid, who wasn't even there to see it break.
. The title of this chapter said aloud is Nyaa-kuza.