Cave Story/WMG

Substance abuse

 * I originally thought, based on the flower petals you find in his house and his alleged combat prowess, that the Mimigas had a slightly overly rosy view of Arthur's demise and what really happened is he was forced to eat too many flowers in order to fight the Doctor, lost, was warped by the Crown and became the Red Demon; a fellow troper pointed out evidence to the contrary, but the flower petals still bugged me. It's unlikely that before he was killed, he was dropped in his basement and force-fed red flowers. But why would the alleged hero of the Mimiga village eat these things willingly? Especially if he was as ignorant as most Mimigas about what they really do? But then remember what the Doctor tells you about Red Crystal. It draws out one's latent powers, but also crushes one's faculties of reason. Doesn't that sound a bit like steroids meets phlebotinum?
 * I figure several Mimigas have been dosing themselves with red flowers in small quantities independently of the Doctor's machinations. Arthur, for one, and probably also the one in the hanging house in Grasstown (because you don't even necessarily have to fight him, and what stake would the Doctor have had in dosing him so early?). Igor, too, though he's probably still a victim; the Doctor has a vested interest in keeping an eye on those eggs, and Igor's note on the computer sounds like it was composed by someone fairly rational, so the change to the form in which you meet him must have been recent. (He and Toroko also both shrink to their original size when you beat them, which, aside from indicating they were both dosed all-at-once, is more sympathetic than what happens to the smaller, nameless one in Grasstown, who has presumably been doing flowers for a bit longer and in a smaller total amount.)
 * The fact that they're usually found scattered around beds (except in Arthur's case; he grew and used his flowers in the basement because he'd have had to conceal his habit from his sister) makes me think that they're highly addictive (one's bed is a personal thing, associated with a necessary and similarly personal habit) and that withdrawal is an absolute bitch (so habitual users are dosing themselves first thing in the morning). And it follows that the exact nature of the changes caused by the flowers is determined by how much you're taking, relative to your body, and if you've built up a tolerance- Igor is an adult Mimiga who had already been taking flowers for a while before the Doctor fed him the rest and hulked him out, so he gets the fully-increased size but is a bit of a pushover. Toroko has far less body mass, and she's never taken flowers before, so she turns into a serious threat.
 * And remember how Toroko's eyes went deep red right before she hulked out? Did it never bug you that King, another excellent fighter (though still not a very tough one- Misery shredded him without even going into "battle mode", which is more evidence that Mimigas need red flowers if they're going to do any fighting at all), who occasionally acts in rather irrational ways (as pointed out by a similar but less comprehensive WMG below), is the only Mimiga we see with eyes of a different color, and that it happens to also be reddish?

Every WMG on this page is true
My reasoning behind this is that the guy who made the game specifically made many details of the game vague, so that the player can fill them in for themselves. The entire point of WMG is to fill in the vague details of a story or work. Put two and two together and you have a quite obvious truth. The only ones that are NOT true are the WMG's that contradict each other, in which case the more credible one wins out.

Malco is a Bomberman.
Seriously. He himself states that all he can do is make bombs. The square design is probably what you would see if you took off any Bomberman's casing.

Cave Story is a sequel to Earthbound, with the basis that Giygas defeats Ness.
At the end of the Earthbound game, Ness and his friends have their souls deposited into robots and are sent back in time to fight Giygas. The premise is that Giygas succeeds against Ness, and receives a massive burst in power, but he does not manage to destroy the world. Instead, Giygas winds up infusing himself into the existing world, creating the new world where Cave Story takes place. Everything in the world is left the same for the most part, except that the future is altered completely by the fusion, meaning most of the events of Earthbound never happen, and Giygas becomes a force of nature that runs through everything and everybody. Pokey is captured by Giygas before he has a chance to escape to another point in time, and gets an ironic punishment for his arrogance by being transformed into Balrog on accident. Ness is left inside his robot body and cast into the new world, where he is discovered by the government post-Giygas and has the robot body remodeled into Quote. The same happens to his friends, with Paula remodeled into Curly. This would explain why Quote and Curly are different from the other robots created to fight the Mimigas/destroy the Crown. The floating island and its residents are actually Giygas’ Magicant, which was given physical form because of Giygas’ victory and fusion with the world, turning everything inside his head into physical reality. That means that the Mimigas, and all the enemies in the game, are all incidental creations of Giygas’ imagination. The Core of the island is a physical artifact of what remains of Giygas’ mind, which is why the Magicant island falls once the Core is finally destroyed. Giygas, as mentioned before, becomes a force that rests inside of all the creatures on Earth. (This force can manifest itself as overwhelming rage or magic.) However, because he has no form of his own, he does not have his own sentience and intellect he can operate on his own. This leaves him at the mercy of chance that someone will be possessed by him on accident to fulfill his wishes. Ballos is an example where a person is pushed to their breaking point and taken over completely by Giygas. The Demon Crown was invented as a kind of extension of the Devil’s Machine to keep a piece of Giygas sentient in the world of his own will. When Ballos and the Crown are destroyed together, this sentience is demolished and Giygas is left to flounder as an untapped force again.
 * Also note how the Doctor becomes red mist after you beat him. Now, who do we know that's also made of red mist?...
 * HOLY SWEET ZOMBIE Crystal Dragon Jesus A ONE HUNDRED PERCENT PLAUSIBLE LINK BETWEEN TWO SERIES IN A WMG! RUN! RUN FOR YOUR LIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIVES!

Quote had a hidden imperative to take out Ballos
The speech you get in Hell about Ballos has no obvious speaker, but it couldn't have come from nowhere. The obvious path is to assume it was that dog at the end, but that doesn't account for the speech beginning after you first defeat the core but then stopping. Instead, a more comprehensive explanation is that it was a recorded conversation set to begin playback if and when the core was destroyed, to instruct Quote to find and kill Ballos. The conversation starts when you inflict critical and presumably lethal damage on the Core in the Labyrinth, but stops when it somehow senses that the core has been repaired. When you later defeat it in the throne room, it plays out in full. It's set to play after destroying the core, of course, because killing Ballos becomes an imperative as soon as the core is destroyed--if Ballos lives but the core doesn't, the island falls to earth, with what the recorder must have assumed would be disastrous results. Moreover, the conversation is not the full extent of this secret imperative, because by the time it begins quote has already stopped following Sue, and stopped moving towards safety, to enter hell. He knew he had to go there already, the message was just a formality (or alternately a friendly gesture, as opposed to just forcing him to do it because his programming said so).
 * Also note that Curly didn't hear the message. She had to be told by Balrog about Misery's hand in creating the Demon Crown, which was part of the message.

Alternatively, the messages in Sacred Ground were from the dog.
The sparkling dog who waited outside the Seal Chamber and asked you to kill his master, before teleporting away.

Curly is a severely damaged robot, and not just memory-wise.
I take no credit for this, see this forum topic. Basically, Curly does a number of things which are illogical and irrational, dangerous, and not befitting of a robot with a purpose such as her own. Upon seeing Quote enter Sand Zone, she immediately recognizes him as a threat to the Korons but rather than confront him well away from them retreats and lets him come right into their home, at which point she attacks him without waiting for any indication of intent or response to her accusations. Right in the middle of the children she's trying to protect. When he beats her, she's extremely quick to trust him, even offering to trade her useful machinegun for his battered and incomplete Polar Star, without prompting. Later, in the Labyrinth, she fails to recognize Balrog as a threat even after he explicitly states that he intends to turn her into scrap metal, even after he attacks her. When you beat the core and the room fills with water she just freezes up. She doesn't try to find a way out, she doesn't try to bash the door down, she doesn't even respond to or look at her partner. She just stares at the wall, apparently overwhelmed, until something clicks and she decides to try and save Quote.

It's unclear if the mushroom cured her or not, because other than filling in Quote on what she recalled, her only actions after that are somehow getting to hell, helping Quote in hell, and wanting to retire to a quiet location with her new friends once it's all over. Charging into hell in her damaged state probably isn't indicative of a clean bill of mental health, but with both legs broken it's unlikely she COULD have gotten there of her own volition, so it's non-conclusive, and the other actions are pretty justified.
 * Well, it's possible that Curly is a prototype(as in not all the kinks worked out) and Quote is a production model. This also explains how she got to Sacred Grounds;maybe whatever superpower was running the Ridiculously-Human Robots program was experimenting with Villain Teleportation. Since they were working on Villan Teleportation, the device ends up taking a massive toll on whoever uses it;hence why Curly is so beat up when you find her.

Ballos created Balrog.
Well we know why Misery is connected to the crown, but why Balrog? What about him connects him to the power of Ballos? Well, he's a magician, right? Maybe he has the power to create monsters (in fact, he does create numerous red bats and other things during the final fight). Balrog's status as a being is never fully explained, but we do see at the end that he has Bat Wings, and we know that Ballos can create bats. Also, Jenka knows who Balrog is, so maybe they used to be on good terms before Ballos went insane.
 * This troper is led to believe either the thought that Ballos created Balrog, or that Ballos and Balrog are related somehow. Hints for either include but are surely not limited to the following: 1. The first half of their Name's the Same, 2. Both are related to shapes: Ballos can change into a giant sphere, Balrog is a living rectangular prism with limbs and Bat Wings that could've been part of him all along or granted to him by Ballos at any time, or upon his creation, and 3. They both have designs around their eyes (Ballos has the "scar" lines going from above to below his eyes, Balrog has those pink rectangular lines going up and down his entire face past his eyes). They could either be related or Ballos created Balrog somewhat to his theme and image, but using a different three-dimensional shape. Balrog being created seems to be a more likely theory.
 * Upon a second thought, perhaps Balrog is some extension of Ballos's personality, a part of him manifested into living form that harkens back to his days before he was sentenced to imprisonment. Balrog seems to get the short end of the stick at times (a slight hint to Ballos's treatment by the King, but not as severe obviously, i.e. in this case Ballos is in the King's position now while Balrog is helpless in what was Ballos's position back then) and seems to be picked on by Misery (him being her punching bag so to speak; isn't that what he was called in the credits?), which could be influenced by the Demon Crown's hold over both of them as willed by Ballos. He somewhat reluctantly (but consciously) helps Quote and Curly in the Labyrinth (yes I know it may have been just to spite Misery since she put him down there, but still), perhaps hoping that they can destroy Ballos and set that part of his spirit free, destroying Ballos and enabling Balrog to live in peace without Ballos and his deranged mind subconsciously affecting Balrog (i.e. when Balrog feeds Toroko the Red Flower with little outward concern), and of course hoping they can destroy the Demon Crown and freeing both him (and Misery) in a different way. If Balrog is an extension of Ballos yet has none of his memories and is just someone that was created and is being controlled by some psychic link, he also has less reason to stay behind with Misery and Jenka because all he knows now is that Quote and Curly destroyed both the thing keeping him (and Misery) around, and the bad influence of Ballos on his mind, and he wants to be with his twice-saviors. It also could explain why Balrog himself smashed his way into Hell to save Quote and Curly instead of/without Misery because he was doubly indebted to them. All of this can be reinforced by the fact that Ballos wants to die, so through Balrog is he helping bring himself closer to his desired death and freeing his tormented soul when he realizes that Quote and Curly may just be able to put him to rest.
 * Possible further support: In the Nicalis translation, Balrog greets Jenka as "Auntie" at one point. Either Balrog meant it as an honorary title, or he regards Ballos as his father in some sense.

Every Mimiga on the island was originally human
Okay, we know by the end of the game that Sue and Itoh used to be, but what about the other Mimiga? Are we to assume they just existed on this floating island forever? We know that, so maybe instead of  , it occasionally did something like   After all, the Red Crystal can  , and we know that The Doctor. And on that note...

King is the king that had Ballos put to death
Going with the theory above, if some of the  were instead , and we don't know how long ago this was or how long a Mimiga's lifespan is, then King   The fact that none of them remember being   could be attributed either to.

The weapons run on Spiral Energy
For those of you who don't know what Spiral Energy is, put simply it's the power of evolution. Positive emotions like joy, hope and admiration increase its power, while negative emotions like sadness, despair and fear decrease it. However, only Spiral beings (AKA lifeforms that have evolved from Spiral Engergy) can generate it, which kind of kills this theory since the main character in Cave Story is a robot. Fortunately, even though robots are unable to generate Spiral Energy, that doesn't stop them from using contraptions made from it. Those little yellow triangles that the enemies drop are actually their crystallized Spiral Energy released upon death, which gets absorbed into the gun and, eventually, allows the gun to evolve into a more powerful form. Likewise, whenever you get hit, this causes the Spiral Energy to weaken and eventually forces the gun to de-volve. SCIENCE!
 * Then explain how the Sword evolves.
 * It's also established in Gurren Lagann that Spiral Energy makes no goddamn sense. Hell, the term Spiral Energy is actually a substitute for the term A Wizard Did It!
 * I guess that makes the black wind in the Real Last Cave and the Sacred Grounds the Anti-spirals influence?
 * And in addition, the Nemesis runs on antispiral energy, which is why it gets weaker when it levels up. It was also named Nemesis after the Spiral Nemesis. The goddess referred to in the description is also not a literal goddess. It's referring to.

"Misery" is not her real name.
Oh sure, that's what nearly everyone calls her. But Jenka, her mother, never calls her Misery (or by name, either). Chances are that Misery is a nickname based on her state of life since the Demon Crown was made, that was given to her by either  or the first crown bearer and stuck fast.
 * Her Japanese name is "ミザリー, Mizarī" according to The Other Wiki. Anyone know if that translates to anything? I'm presuming the translator just swapped it to "Misery" because it looks and sounds nearly exactly the same.
 * That's katakana, the Japanese syllabary mostly used for foreign words. It's meant to be "Misery", and those are the closest sounds they have.
 * One must really wonder whether it’s a reference to Misery in some way....
 * Perhaps her name was originally something pleasant like "Mystery", but with the creation of the Demon Crown and her soul being enslaved, "Misery" became more applicable? Perhaps to show how she had changed and/or the Crown had changed her? i.e., before the Demon Crown, she had a reputation as something of a do-gooder? So calling her "Misery" is a way of showing just how far she's fallen?

Kazuma's attempts to chat with Sue at the very beginning were what woke up Quote.
Kazuma's chats were sent wirelessly, and they just happened to be the right frequency for Quote to pick up. Hence why those cutscenes were prefaced by "Incoming transmission".

Jenka, Ballos, and Misery are not just witches/sorcerors, they're demigods.
Bear with me here. Clearly, the resemblance indicates that Misery (and therefore Jenka and Ballos) are related to the goddess Nemesis.
 * * They could well be Maiar, to be precise.
 * On the inventory screen, the Nemesis gun is referred to as a weapon from the goddess. What goddess?
 * The Greeks had a goddess named Nemesis, a representative of divine retribution.
 * On the Balcony of the island, there is a statue of a winged woman, who could very easily be Nemesis herself.
 * Said statue also resembles Misery (albeit with wings), and appears to be holding a staff, like Misery and Jenka.
 * The involvement of a goddess of divine retribution also fits thematically--those who abused Ballos' power all came to bad ends. "Well, you reap what you sow."

Balrog is a Platonic Ideal. Balrog is Balrog.
He is not a robot, or a toaster, or a suitcase, or a lunchbox; rather, all of those things are imperfect shadows of Balrog. Balrog is eternal and thus, indestructible--this is why he's able to smash through ceilings so easily, and how he fights Quote more times than anyone else and lives to talk about it.
 * Actually, he's soap. Word of God even confirms it. Unless...all those things are...imperfect shadows of...soap?

Ikachan takes place on the island.
The Ironhead boss is Ironhead himself, and all the squid are members of Ikachan's species. Whether it takes place before or after Cave Story is up to you.

Balrog is a bar of soap.
We've heard it from the man himself: What inspired Pixel to create the character of Balrog was a bar of soap. He mentioned that the process of his creation was just him taking (figuratively speaking) a bar of soap and adding arms, legs and a face to it. The main question now is: If Balrog is soap, does Misery bathe with him?
 * That would bring rule 34 and a lil squick.

That tow rope in the Core chamber...
...is in bad shape and decaying rapidly. So if you stop to help Booster, or if you wait until after your post-Core-fight blackout to look for the rope, then it decays to uselessness in the interim and becomes Lost Forever. Collecting the rope as soon as possible and placing it in your Bag of Holding somehow prevents the decay temporarily, leaving the rope just strong enough to bind two robots together, but just weak enough to break when dramatically necessary. Thus, it holds up for the duration of the Waterway, then breaks after the fight with Iron Head; the pieces are strong enough to be reused in Sacred Ground, yet break again after the fight with Ballos.
 * Actually you can wait until after you defeat the core to get the tow rope, you just cant wait for curly to give you her bubble.
 * Actually actually, the tow rope disappears as soon as the fight with the Core starts.

Ballos's magic created a Lotus Eater Machine
To escape his suffering, he used his magic to create an illusion that would keep him happy. At this point Ballos's magic becomes an entity of its own and destroys anything that would break the illusion or harm Ballos. The king, Ballos's family, and everything in the vicinity were instantly destroyed because they would remind Ballos's of his terrible suffering. After Ballos is defeated he regains his senses and those are his only true lines in the entire game. The lines spoken before the fight are illusion created by his magic.

If you jump down to help Professor Booster...
Quote lands ON him (storywise) and horribly shatters his fragile old man spine. This is the most logical reason I can think of for him to only die if you jump down and talk to him.
 * Or he could be so exhausted that the simply act of talking and handing the Booster 0.8 is enough for him to give the points.
 * Perhaps if he has the booster he can use it to escape (which he feels he must to get you the equipment you need for your quest or something) and get some medical treatment (there's a supply station you can only access with the booster/machine gun nearby after all). If you meet him, he's lost both his means of escape (the booster) and since he's done what he feels he needed to (give you a vital piece of equipment) less motivation to try. For all intents and purposes he's dead and useless so he just accepts the inevitable.
 * Sounds extremely plausible. The Booster jetpack apparently is his life's work (Heck, it's even named after him! Also, he worked on it for a long time.), and when Quote, as he thinks, needs it much more urgently than him, he gives it away, therefore can't finish it and thinking that there's nothing anymore for him to do for his cause, doesn't attempt to leave the pit.
 * The "he escapes on the Booster" explanation doesn't hold water when you consider how he meets up with Quote if you didn't talk to him: he arrived in Mimiga Village by teleporter. If you take that same teleporter from Arthur's house to the Labyrinth afterward, you end up in the exact pit Booster fell into, which initially doesn't work if you examine it before getting the Booster. So, it's likely that if you don't get the v0.8, he repairs the teleporter, which, actually, could mean that he used spare parts from the v.0.8 to fix it. As for how he managed to upgrade it simultaneously...

Cave Story takes place in Zimbabwe
Magical flying "castles" and talking "bunnies"? Sounds like Zimbabwe to me!

Kazuma Sakamoto may be the one who destroyed the Egg Corridor
The situation was going from the bad to the worst and in a desperate effort to hatch the Egg N.00 he may have done something that did hatch the egg but caused the rest of the place go crazy and blow itself.

How can a robot and a Mimiga have at each other?
Simple. They don't. Because they can't.

Think about it. Quote (and Curly, for that matter) were built for the purpose of raiding the Island and destroying the Demon Crown. Why the hell would anyone make a battle robot even capable of having sex when it has nothing whatsoever to do with its intended purpose?

Given Quote is completely unable, that leaves the question of why you're left with Chaco's lipstick after the fact. Well, while not capble of sex per se, Quote is capable of making out. It's possible said Optional Sexual Encounter consisted solely of lotsa kissing, and when you have your arms wrapped around each other, it'd be easy enough to slip something as small as a lipstick tube in the other person's pocket.

Incidentally, at this point Quote (and the player) doesn't know he's a robot. Given he hasn't encountered any actual humans at this point, it might be he thinks at Grasstown he's some sort of Mimiga, if only because he can't think of anything else he might be. Which would explain why he would start making out with her in the first place.
 * I've got an even simpler one: Quote just took the lipstick in case he needed to write something later on.
 * There's also plenty of alternative uses for various robotic parts which Chaco would be able to figure out.
 * Alternately Chaco got annoyed at a stranger sleeping in her bed and decided to play a prank on him by slipping her lipstick into his pocket and snuggling up next to him to make him wonder just what happened last night.

Health Packs are actually Batteries
]] Quote is a robot, and as such probably doesn't get much from an arbitrary human Health pack. Either the Health packs are batteries scattered during the robot war or else a form of "Upgrade" of some sort placed for the same reason. This could explain in a logical way why the hard mode Quote with human skin and hair doesn't get to use them. Hard to pick up much benefit from a battery as a human, isn't it?

King is afflicted with a controlled form of the Red Flower's Curse.
Think about it. He's the only non-Frenzied Mimiga that has glowing Red eyes (Orange, actually, hence partially changed), he has a very nasty expression on his face at all times (more like a rabid dog than a rabbit), at times he is very irrational/over-emotional, making rash decisions out of anger (locking up Sue, threatening Toroko). It's almost as if he's got some kind of roid-rage that he's trying to keep under wraps. Red Flowers have been shown to exist in his village, stored at Arthur's house. Isn't it possible, perhaps even likely, that King is afflicted, but supressing it somehow? Perhaps that's what his Blade did while he was alive? Kept the affects of the Red Flowers at bay? Perhaps that's why it contained his ghost when he gave it to Quote? Because the Blade had properties that were keeping his spirit intact or something along those lines?
 * If this is true, than the other mimigas made a huge mistake by letting him be the leader of the village.

The Doctor is Lord Genome's Evil Twin.
They're both Mad Scientists bent on world domination (although Lord Genome succeeded while the Doctor failed), they both have dark skin, the Doctor has a bulky Muscle Doctor form while Lord Genome is naturally buff, and the Doctor's energy attacks are red, while Lord Genome is the only character in the series to use red Spiral Energy instead of green. Not to mention both of them are connected to "The Surface". The reason that they're twins instead of the same guy is that the Doctor has hair and is clean-shaven while Genome is bald and bearded, they both die at the end of their respective media, and the Doctor is a Complete Monster while Genome is a Well-Intentioned Extremist.

Misery wanted out, and was deliberately sabotaging the Doctor's plans.
Prior to the boss fight with Misery, she declares that she has no particular love for the island, and that she's only fighting Quote because she was ordered to do so. It's entirely possible that this is an attitude she had held for a long time. She had served three Crown Bearers before the Doctor--plenty of time to get sick of servitude. So by the time she was in the Doctor's thrall, she was beginning to think that insanity or death would be preferable: this is why, in the Sand Zone storehouse, she offered to test one of the Red Flowers on herself.

Shortly afterwards, Misery found a reason to hope again: a girl robot in the Sand Zone who put up a darn good fight when Misery came to take away the mimiga children, and a boy robot who survived a fight with a red-flower-frenzied mimiga--two robots who now had a beef with the Doctor and who appeared to be actually strong enough to kill him. Due to her orders, Misery couldn't simply let them go, so she threw them in the island's trash heap rather than killing them, hoping the robots would stay put until she could find some way to use them against the Doctor. Quote and Curly attacking the Core was a possibility she never even considered; this attracted the Doctor's attention, and Misery was again forced to deal with them. Again, she half-assed it; instead of directly killing the two robots, she just flooded the chamber--an act that caused the Core chamber, and the exit from the Labyrinth, to reopen.

It's hard to say whether, during the boss battle, Misery deliberately threw the fight against Quote. Depending on the Doctor's orders, it's possible she was compelled to really try to kill him.
 * Dear god... that gives me an idea for a fanfic! TO THE BAT-MICROSOFT WORD!

Curly Brace owns the original Nemesis.
That Nemesis gun Quote gets from Mr. Little? Just a poorly made knock-off. It even has the levels in reverse. No, the Nemesis that Curly is using in the Bonus Level of Hell is the original, and she's owned it ever since she's been created. She didn't use it before because it was levelled down to the rubber duck-shooting stage and she didn't remember its true potential. Basically, she used it as a bathtime toy. When Quote restored her memories, she levelled it up and since she can't get hit in the Sacred Grounds, her Nemesis can't level down. And that "Goddess" description? Made up by Mr. Little to sucker Quote into the exchange.
 * Or, Mr. Little is a few inches tall and Curly Brace is a golden-haired, ridiculously human, killer robot armed with a gun that shoots lightning. It's entirely possible that he genuinely mistook her for some kind of goddess.

The Red Demon in the Last Cave IS Arthur
The Facts : There are red flowers in the bottom right corner of Arthur's house. He defeats this monster which has been massacring loads of Mimigas for a while, and everyone's happy, but he dies. And for some reason the Red Demon is still around. The Theory : When you fight Frenzied,   turns back and dies after you win. Now, if the original Red Demon was a Mimiga once too, then when Arthur defeats it (under the influence of the red flowers), then it would turn back into a Mimiga. A probably very cut up Mimiga. Arthur (now the Red Demon) would've run away. Seeing that the monster had gone, the people would've gone to the body. If it was scarred beyond recognition, then they would probably think it was Arthur. And so they buried it, while a Frenzied Arthur somehow got to Last Cave (don't ask me how). Either this or Red Demon is a species.
 * It was mentioned by Jack (in an optional piece of backstory, see "The Great Hero Arthur Part 1" here) that Arthur didn't fully defeat the Red Demon, but just drove it back. Additionally, Arthur was (allegedly) killed by the Doctor's goons (whoever exactly did it) and not by the Demon. And to me, the Red Demon looks (and behaves) extremely similar to a frenzied Droll (those plantation trolls)...

Misery is conditioned by the Demon Crown in a similar way to GLaDOS.
She gets a feeling of euphoria whenever she does what the wielder of the Demon Crown tells her to do. Which explains why she says "Heavens, that felt good!" whenever she does so.

Jenka created Balrog
Word of God states that Balrog is soap. Jenka owns numerous dogs. Dogs, as most dog owners can attest, need baths. What do you need for a bath? Soap. Jenka probably created Balrog out of soap as an outlet for her daughter Misery's cruelty, which is why Balrog is Misery's chew toy. When that failed to stop Misery from forcing Ballos to create the Demon Crown, Jenka just gave up on her.

Igor didn't die after the 2nd boss battle
After you defeat Igor in the egg corridor, you see him shrink, and then collapse. But his "corpse" never dissapears until you leave to another area, meaning you just knocked him out. After you leave, he somehow eats another red flower and takes a teleporter to the balcony, where you kill him off for real.

Curly is still alive in the normal and bad endings.
You never see Curly start to blink and then disappear for good. She just lays there, unconscious.
 * Though she is still submerged in water (or surrounded by water, if you dropped her in the cabin), so she will probably never get to wake up again, or in case of the cabin, be trapped there forever without any method of escape.

Cave Story takes place in the Chrono universe.
In the Hidden Last Cave and Sacred Grounds, your weapons drop to level 1 when you feel a "black wind." This wind could be the same black wind that Magus and Schala are able to hear/sense. The black wind seems to be associated with impending doom or death, both of which describe the things going on the island. Or perhaps Ballos' magic is causing the black wind, since both of the areas where your weapon levels drop happen to be connected to his magic. Furthermore, Jenka, Misery, and Ballos could either Mystics or descendents of the Enlightened Ones.

Quote and Curly weren't originally designed to be military robots at all.
Let's look at the facts: Quote and Curly more or less have no different physical capabilities than your average human does. No armor plating, built in weaponry, superhuman strength (together, they can't even remove the boulder in the labyrinth), or what have you. If anything it seems like they were designed to emulate humans and nothing more. Possibly some idealist scientist built them for that reason, but then somehow, they were trained for military purposes after they were created (after all, they can learn) and given the mission to destroy the Demon Crown.
 * The only other robots we've seen on the island look noticeably less human than Quote and Curly do, and several NPCs have presumably mistaken Quote for a human before Booster revealed his true nature. That is, Quote and Curly are unique in that they're Ridiculously-Human Robots. They even wear human clothing. (Why would a combat robot need panties, anyway?)
 * Not only do the scrapped soldier robots near the island core look nowhere near as sophisticated as Quote and Curly, but the damaged one who speaks to you before the boss fight does so in a purely mechanical fashion, as opposed to Curly -- who talks and acts like a human. Quote and Curly can think, reason, and feel emotion, and seem to have free will, which sets them apart from the soldier team that attacked the island core room -- it's safe to assume they're at least entirely different models from the soldiers. Combat robots shouldn't have empathy, they should be killing machines, and Curly's lines when you defeat her indicates that combat robots are heartless "mimiga butchers".
 * Quote and Curly don't seem to have any built-in features that aid their combat ability. They fight entirely like humans do, wielding weapons in their hands and presumably all the equipment they use (like the Booster v0.8 and v2.0) are externally mounted/worn; thus, Quote can easily equip or unequip them at a whim, without needing someone to tinker around with his internal systems. The lack of things like say, Arm Cannons, Deflector Shields or anything of the sort makes it seem less likely that they're military robots.
 * As indicated above, the incident with Chaco wouldn't be plausible for a combat-oriented robot as it wouldn't make sense to add that kind of "equipment" to a combat robot. But if we assume that the two weren't built for combat, it makes a lot more sense that they would.

Quote and Curly had at each other before Quote lost his memory.
Assuming that they were designed with those capabilities (which is implied considering what can happen with Chaco), it would certainly explain why her panties are there, wouldn't it? The way I see it, they wanted to find a secret, private place, so they went behind the wall where nobody could find them. I leave the rest to your imaginations. Though, to play devil's advocate, it could've potentially been anyone or possibly even the result of a practical joke. (Panty theft?) But it would make sense if they figured that they were going to fight a powerful opponent, and had doubts about whether they were going to survive, let alone win...

The Plantation (and all obviously connected areas) is connected to the Waterway (and all obviously connected areas
It can be inferred that the Plantation is linked to the Waterway and, hence, the Mimiga Village, because Sue escaped from the Plantation and eventually washed up in the Reservoir... where Quote ended up following the Waterway section. There's a pipe in the pool at the bottom of the Plantation that you can enter, but can't actually leave the Plantation through; perhaps the Doctor had someone install a grate after Sue's escape. As for how she didn't drown, we only end up in the 'Waterway' after messing with the Core, which directly or indirectly has some control over water levels, as seen in the fight and the flooding that occurred afterwards. The house down there suggests it wasn't always so wet, either. There were probably more air pockets there when Sue escaped.

Curly mistook herself for a human.
This would explain why she's in possession of panties. The place where Quote found her panties was the strangely-placed equivalent of a closet where she kept all her spare clothes, and Quote either is a perv or he for some godforsaken reason decided to take a random object sample from that strange hidden nook behind the wall out of robotic, scientific curiosity, which, due to Rule of Funny and Japanese humour, happened to be panties.

The Doctor is a Time Lord
Because it's too obvious not to be true.


 * Does this mean The Master will become the villain if the sequel is made?

Cave Story is a distant sequel to Gun Girl 2
And why not? Both games have the same basic play style, weapon upgrade system, etc.. Besides, who knows what happened to the world after nearly everything was destroyed by Hell. What was rebuilt was probably like nothing we'd recognize anyway. Hell seeping into the world may even be why a lot of they mystery artifacts, such as the crown, and why odd creatures exist.

Booster is working behind the scenes to help Quote through Xanatos Speed Chess.
Booster was on the island for at least a year with the Sakamotos. During that time he did research and learned about the robots from the past, and their workings. Possibly, he and Itoh set the computers to work on the same frequency as those robots. Itoh is an engineer of considerable talent, he could have adjusted the frequency easily. Booster would have thought it interesting, as a "just in case" experiment. The communications between the computers was what woke Quote up, but Booster didn't know it at the time. When he saw Quote, however, he instantly knew what he was, and sent him to the Sand Zone in the knowledge that if anyone had a chance of stopping the Doctor, it was him. When Quote is captured, Booster checks Quote's signals and finds that he's still alive. Booster, having access to the island's computer network because of Kazuma's help, confers with the guard robots and asks if they have seen Quote. They have, and Booster teleports to the Labyrinth Shop. Misery detects the unfamiliar magic (namely Booster's) among the familiar and goes to intercept Booster. Booster had been carefully evading her his entire time on the island, knowing he stood no chance against her and that she would likely kill him if she found him. The two of them fight, Misery intending to drop him past the Boulder Chamber. She wins and starts to teleport him, but he manages to stop himself before he reaches there and fall into the big place where he falls. Misery figures the fall will cripple him and he'll die, so she lets him be. At this point Booster senses a strong magic, but can't focus on it due to being in pain. If Quote goes in after Booster, Booster will give him the 0.8 and die, figuring he needs to do what he can to help Quote. If Quote doesn't, Booster gets desperate and uses parts of the 0.8 to repair the teleporter, wanting to at least get a message to the Sakamotos. They heal him up, and Booster checks on Quote's signals and finds that he's still alive. He teleports back to the place where he fell and realizes that that magic he felt was really the Core. He then deduces that Quote may have to go in there and casts a spell to strengthen mechanical items in the room. This strengthens the metal tow rope against decay, and repairs it a little. When Quote and Curly arrive it works on them, too, but neither of them notice it because the battle is so intense. It's what allows Curly's air tank to withstand the fight even when in use. Quote gets the tow rope, which would have decayed without the spell, and they fight the Core. When Quote blacks out, Booster sees him come back online, believes he is likely damaged, and sends a transmission to the Waterway, which Booster knew was the fastest way out of the Labyrinth due to using it as a study site at some point in the past.


 * Alternately, Booster was some manner of technopath wizard who tried to stop Ballos with each group of humans that came to the island for the Crown. He just never had success before because Quote was smashed last time.