As a Fridge subpage, all spoilers are unmarked as per policy. You Have Been Warned.
- Fionna's last name is "Campbell" instead of "Mertens" due to Minerva and Martin having switched genders as well.
- Farmworld Finn's family has a pot of perpetual stew that's been brewing for years, mentioned to be the soup "mom was cooking the day she died". The identity of the mom is left ambiguous, but the fact one of the kids has red hair and green eyes suggests it's the Farmworld version of Huntress Wizard. Another is the perpetual stew: an alternate name for it is hunter's stew.
- Fionna being able to text back to her home dimension despite being in an entirely different one isn't all that far-fetched. Her reality is travelling alongside her after all, inside of Simon's head.
- Despite everything else having been reduced to nothing in the world the Lich wished for, Billy's corpse still persists hanging off the Lich's form, with the only major degradation being his eye hanging shriveled out of its socket. But then again, why would it decay? All life is gone now - including any microorganisms or fungus that could've started on decomposing the Lich's Billy-Corpse Suit. The only reason everything else is "decayed" is the Lich's wish instantly killing all life and reducing it to bone, as we see in that universe's Ice King's tapes.
- The Ice Crown and Bubblegum's crown are both found with their jewels inside them, despite the fact that they had to be used in order for the Enchiridion to allow travel to Prismo's Time Room. However, at the end of "Jake the Dog", the jewels return themselves to their crowns once Finn and Jake return. It's likely at some point before or after Jerry came back that they did the same in this reality.
- Martin still being present in Ooo in the Vampire reality may seem odd at first considering he was shown to be from Founders Island in the main universe, but take this in consideration. With Marceline being raised into evil by the Vampire King, she wouldn't have helped Two Bread Tom (the founder of Founders Island) and his tribe of humans escape from Ooo which likely means Founders Island never formed in the Vampire reality and the human survivors and their descendants were forced to live their lives out in Ooo instead.
- Why does Fionna do the obscene V-sign gesture? Her father is (presumably) the gender-swapped version of Minerva Campbell, who was voiced by an Irish actress.
- There is a retroactive brilliance to the "Five Short Tables", the Fionna and Cake versions of Cuber's Graybles, being told by the Ice King rather than a genderflip version of Cuber. As Cuber is from a thousand years into the future of Ooo, introducing a Fionna and Cake counterpart of him would've set a Foregone Conclusion for their world, which now in this series would've lessened any suspense over what that world's ultimate fate will be.
- The Lich's situation in "Jerry" gets an extra layer of irony when you remember Billy. Billy used to sit around in his cave on a pile of treasure and used to believe that fighting evil is pointless. Now the Lich is sitting in a cave on a pile of bones, still wearing Billy's skinsuit, and depressed because he wiped out all life and has nothing to do.
- Given the fact that Fionna, Simon, and Cake likely brought microorganisms with them to the Extinct World, it's entirely possible that life might arise there again one day which would further render the Lich's mission pointless and show even deeper why he will never succeed.
- Fionna and Cake both have some shipping tendencies, being entirely supportive of the enemies-to-lovers dynamic of Little Destiny and Jay, and Cake telling Simon and the Winter King to kiss. This makes sense when you remember Ice King used Fionna and Cake as a platform for shipping.
- This also explains why Fionna dreamed about an "Ice Prince" and quickly developed a crush on Winter King: the Ice King constantly imagined her being infatuated with him.
- The Ice King's obsession with kidnapping princesses came about from the madness of the Ice Crown warping his desire to see Betty again, his "princess", and that she would love him again. Princess Bubblegum, however, was mostly shown to hate the Ice King in the early seasons, making her obsession with him as Candy Queen feel bizarre. Once it's revealed that the Winter King transferred his madness onto her, however, it all begins to make sense. Candy Queen likely knew that WK was the one who cursed her with her madness, which subsequently warped that idea into an obsession with him. He indeed was the Key Ingredient to Candy Queen's problems.
- When Cake flips through the channels on Prismo's TV, she sees Lemongrab try (and fail) to get his Lemon Camel to drink a glass of water. You know what they say: "You can lead a horse (or camel, in this case) to water, but you can't make him drink."
- Casper, the Mirror Character of Simon in Casper and Nova, is designed with bandages over his eyes because he, just like Simon, is so single-minded in pursuit of his goals that he's blind to everything else, including how much the person he loves is sacrificing for him while he's never returned the favor.
- When Fionna and Cake's world is finally removed from Simon's head by GOLBetty, it takes on the form of a dandelion - and what do people do with dandelions? Blow on them to make a wish.
- Fionna wished for her world to be "canonized", but why doesn't it create a reality where it was always "canon?" Because the wish wasn't from Prismo, but GOLBetty, meaning it works on different rules and doesn't create an alternate reality!
- With the exception of Baby World (which was a detour anyway), each of the universes Simon visits has his counterpart factor into a major way and serve as an aspect of the depressive crisis he deals with:
- Farmworld is a universe where Simon sacrificed his life to stop the Mushroom Bomb. In the direct context of Fionna and Cake, Farmworld Finn is a more direct counterpart to Simon as a previous user of the Ice King's crown who deals with the trauma of wearing it. His life also mirrors Simon, only instead of being the only human in a magical world, he is (or was) the only magical being in a mundane world, an experience that drove him to isolate himself and his family.
- The Winter World is a universe where Simon kept his sanity despite the odds, keeping the crown's magic and his sense of self. Initially, this seemed to be a universe that shows what Simon would be like if he had a stronger will… only to reveal that the Winter King only "beat" the crown by forcing its madness into someone else, something that our Simon would never dream of doing. Despite all the trauma it brings him, Simon never once thinks of damning anyone else to the same fate.
- The Vampire World is one where Simon never put on the crown and was killed by a vampire before he could meet Marceline, resulting in the Vampire King finding both and conquering the post-Mushroom War world with their power. Despite Simon insisting that his life doesn't matter, this world shows that it does, far more than he believes.
- The Extinct World is the only one where Simon's presence didn't have an impact—though the Ice King's tapes and crown do prove crucial in reaching the endgame of the story by allowing Fionna to see what Simon was like in that state and realize that forcing him to go back to it just to restore her world’s magic is selfish and wrong, not to mention giving Simon a final temptation by seemingly offering him a “purpose” for existing. No, instead, it's the Lich who serves as a parallel to Simon: the Lich achieved his goal of killing all life in his universe, but it gave him no satisfaction and left him completely purposeless to the point where he rages at GOLB about it- just like how Simon, despite successfully being given a second chance at being “normal”, felt out of place and meangingless in the magical madness of Ooo, not helped by almost everyone outright saying they liked him better when he was the “fun” Ice King and not a “boring sad guy”, even offering to go back to being insane just to bring magic back to Fionnaworld. The fact that both of them see GOLB/Betty as their “god” strengthens this parallel, as she/it probably doesn't appreciate the Lich/Simon going so far for her/it.
- In the flashback in "Jerry", when Simon and Betty embrace each other after he convinces her to not go on her trip, she is one step below him on the staircase, indicating the power imbalance in their relationship. In "Cheers", when the two embrace after making peace with their decisions in life, they are standing on even ground.
- In "Whispers", the Farmworld Lich pulls a Shut Up, Kirk! at Finn's Boring Insult by saying that while the world questions and doubts, he knows exactly what he is. This mentality ironically damns the Lich in "Jerry"; once he realized his one and only goal, he realizes that he has nothing left and relies on GOLB to give him a sense of purpose. In the end, he proved Finn right; he is basic, incapable of changing and improving.
- At first, it might seem weird that Prismo is so depressed over Jake's implied death considering someone with his place on the cosmic scale would likely be able to summon him from the Dead Worlds in some way to hang out. Except Jake was such a Mellow Fellow that he ascended to the 50th Dead World when he died, which Together Again establishes as somewhere near impossible to get into even for cosmic powers like Death himself. Prismo likely wouldn't be able to contact him there either, and even if he could Jake would be so content he wouldn't be able to hang out with him again anyways.
- In the Winter King's reality, his Marceline is an ice construct, like the rest of the Ice Kingdom. However, her Ax Bass is very much real. This does not bode well for the original Marceline.
- In the Vampire reality, we learn that humanity is near extinction and that vampires have become the dominant species. What's worse is that the Vampire King has the Ice Crown, using its power to permanently block the sun with clouds so vampires can hunt freely... but hasn't succumbed to the madness and physical alterations that the crown inevitably causes to whoever wears it, meaning he has the sheer willpower necessary to No-Sell the Ice Crown’s madness indefinitely when all other known holders couldn't. This shows just how dangerous the Ice Crown's powers can be when used by someone who has the willpower to resist the madness, and evil to begin with.
- Assuming, of course, that his madness is not a more subtle hedonism and gleeful disregard of the future; Bonnibel makes mention of the vampires having overhunted their food to the brink of extinction under the Vampire King's rule, and he seems to be entirely unaware of it, which is a far cry from the very conscious and philosophical Vampire King from the Stakes episodes. This Vampire King is a fool leading his people to oblivion.
- As we see in the Ice King's tapes, the Lich's wish to exterminate all life was instant. In a single frame, the Ice King and Gunter were reduced to skeletons. No pain, no screaming, no struggle, not even any awareness. This happened to all life in the universe. One second, life was normal and teeming. The next, gone in an instant.
- No suffering, at least.
- The Dead Worlds in the Extinct World must have had quite the day dealing with every single living being dying all at once. Reincarnation is not possible either, since there's nothing to incarnate to. That is, of course, if the Dead Worlds didn't die as well.
- So what happens to Baby Finn after he was abandoned by everyone in Vampire reality? The tank he's in might be able to protect him, but since it's broken, and the fate of vampires is seemingly leaning in their favor, the chances of his survival are rather slim.
- Thankfully, "Cheers" reveals that he makes it through just fine.
- Considering Martin is already shown living in Ooo in the Vampire reality, what happened to this world's versions of Finn and Minerva? Are they in hiding or were they already killed by vampires by the time Simon, Fionna, and Cake show up?
- Marceline never aided the Founders. Minerva and Martin likely never met, and Finn was likely never born. "Babies will not be born" indeed, Prismo.
- For as traumatic an experience as Simon's life as the Ice King was, it's somehow the best possible timeline out of the ones we've seen. If he hadn't put on the crown, a vampire would’ve eventually killed him, leading to Marceline being adopted by the Vampire King and becoming his top enforcer. If he’d tried to stop the Mushroom Bomb, he would’ve been killed and inadvertently thrown the world into a new ice age, only for someone else to find the crown and endanger the world instead. The one Ice King variant that managed to stave off the madness only succeeded by sacrificing everything Simon stood for and pushing it onto someone else. If things were even slightly different, not only would he be dead, everyone he loves - up to the entire world - would suffer.
- BMO was excluded from the Lich's wish to end all life, so robotic entities don't count as life. Does that apply to the other robots? Most important, does that apply to Minerva Campbell, who uploaded her mind into the Founders' Island? If it does, then she had to witness every human, animal, and plant die in an instant. A repeat of the tragedy that occurred on Hub Island, only worse, as Minerva would be truly, utterly alone.
- The GOLB blocks present a multitude of horrifying implications.
- There's what looks to be thousands of those blocks. Are they all people GOLB/GOLBetty decided had outlived their use?
- The Lich's head was still yelling and writhing as it was encased in the block, and the Lich is noted as being nigh-invulnerable. Is he still alive in there, forced to suffer forever?
- Assuming both of the above are true, wouldn't that then indicate there's thousands of people trapped with no escape, to be forgotten and left to not-even rot for eternity?
- Be pretty funny if in truth those were ALL versions of the Lich who succeeded, fell into ennui, reached Golb to demand vindication, and were turned into basic blocks so Golb could enjoy the silence again.
- Farmworld Finn is implied to become more cynical and withdrawn due to his stint as Ice Finn and the loss of his wife (implied to be this universe's Huntress Wizard/Huntress), but there is also no mention of his mother, father, and baby brother. Did they die in the Time Skip?
- Some fanfic characters straight up don't exist anymore in the mundane world. While Fionna allowing the residents to choose in the climax resulted in them keeping their lives as they are, any characters from the old world who didn't get a mundane counterpart essentially had that choice made for them.
- "Prismo the Wishmaster" reveals that The Marvelous Misadventures of Flapjack is part of the Adventure Time multiverse given that they are both created by Pendleton Ward. Seems innocuous enough, but then you remember that the hand of Farmworld Lich fell into every other universe and the one that fell into the main timeline was still just as sentient and manipulative. Which means that there should be a version of the Lich Hand in a universe completely unused to the kind of threat he poses. And if being part of the same multiverse is as simple as being a series he's worked on, potentially every work by Pendleton at least created before Crossover now has a Lich that, although not much more than a giant hand, is just as cunning and patient a planner as any other version of the character.
