After Frisk accidentally begins sharing their soul with Asriel, the latter is stabilized and is able to come to the surface with them. However, all is not good, and a variety of strange/odd/funny things happen, including President Donald Trump's reaction to monsters coming to the surface, Chara becoming a demon, and a bunch of random side quest things.
As this is a Post-Pacifist fic, most of the tropes from the original game also apply here.
Inseparable provides examples of:
- Arson, Murder, and Jaywalking: Toriel to Asgore after Frisk tries to convince them to stay together.Toriel: Don't call me [dear]. I'll stay with you, you horrible man. But for the children. Not for you. And your tea is very old.
- Berserk Button: Frisk wouldn't hurt anyone, right? Frisk has to deal with their birth family and winds up Save Scumming. Twice.
- Big Bad: Chara.
- Chained Heat: Frisk and Asriel really are inseparable throughout most of the story. A few characters do things to lengthen their chain.
- Child Mage: Victoria, Asmodeus' daughter, is the youngest descendant of the wizards who sent the monsters to the Underground.
- Consummate Professional: Agent Jenkins.
- Donut Mess with a Cop: Asmodeus chases Frisk past a donut shop. It doesn't end well for him until Frisk savescums.
- Eagleland: Type One, played relatively straight.
- Evil Lawyer Joke: Everything Papyrus thinks about lawyers falls into this category.Papyrus: BUT WHAT IF I GET REALLY DRUNK AND HAVE A REALLY BAD HANGOVER?
Frisk: Lawyers don't get drunk! Not good lawyers!
Papyrus: BUT LAWYERS ARE EVIL, SO I SHOULD GET TOTALLY HAMMERED EVERY NIGHT!
- Expanded States of America: Definitely a thing by the end, as it's mentioned that it's now just "The United States" and that the biggest issue is figuring out where to put another star on the overcrowded flag.
- Fantastic Racism: Subverted and mostly offscreen. People kill monsters around the world, but different cultures react differently. At least one kid thinks that monsters are Pokémon and yells at Frisk to tell him how to catch them.
- Fiction 500: The Dreemurr family bank account is enormous. Frisk and Asriel's personal spending allowance is more than they could ever possibly spend.
- Fix Fic:
- Definitely, considering Asriel, Chara, and W. D. Gaster all end up getting saved with absolutely no costs. Even the Amalgamates get untangled.
- Gentleman Wizard: Asmodeus, to some extent. He intentionally plays up wizard tropes.
- The Great Wall: Trump really does build a wall between the USA and Mexico.
- Good-Guy Bar: Grillby's.
- Happily Adopted: Frisk.
- Immortality Seeker: Asriel, for Frisk. If Frisk dies of old age, Asriel turns back into Flowey, and 90 years isn't enough for him. He gets what he wants.
- Invincible Hero: Frisk still has DETERMINATION powers and therefore can't lose. Frisk says this outright multiple times.
- Hilarity Ensues: Frisk tries to explain to Undyne the concept of rain.
- Mundane Luxury: "You can just BUY chocolate?!"
- No Celebrities Were Harmed: It's not always easy to tell who is and isn't based on a real person in this fic.
- Pimped-Out Dress: Toriel has a tendency to put Frisk in these for special occasions. Frisk's response is... mixed.
- Really 700 Years Old: Asgore and Toriel are at least four hundred years old. Asriel experienced an indeterminate amount of lifespan as Flowey.
- Reed Richards Is Useless: Averted. Every aspect of magic and monsters is thoroughly studied and exploited by the end of the fic.
- The Reliable One: Agent Jenkins.
- Save Scumming: Frisk can still do this on the surface world.
- Screw the Rules, I Have Supernatural Powers!: Frisk and, later, Chara can do this openly but try to keep it to a minimum. Not annoying Frisk becomes official government policy.
- Super Senses: Asriel's ears aren't just for show.
- Time Travel for Fun and Profit: Explicitly averted. Frisk doesn't need to do it.
- Title Drop: Sans, during Chapter Two.Sans: You two are going to have to be almost like Siamese twins. No matter how bad things get. Inseparable.
Papyrus: TITLE DROP!
Narration: Where did he come from?
- Unsettling Gender Reveal: Frisk. In spades. Chara too.
- Utopia: Played pretty straightforward towards the end: Monsters have been accepted into society, immortality has been achieved, everyone has a genetically engineered wizard gene, Mars and Venus are terraformed, and the USA encompasses the entire world.