Final Fantasy/WMG

The games all take place in the same galaxy

 * However, in the FF 'verse, humans never came from earth. We don't know where they came from, but eventually they spread out amongst the stars through either magic, science, or some combination thereof.

Every game is a sequel

 * What happens is when a character or an event happens to royally screw up the space time continuom, they create a rip in the fabric of existence and make the next game have more insane and bizarre plots and characters.

Gilgamesh was the reason behind every "crossover"

 * First, Gilgamesh learned how to jump between the FF worlds after being banished into the Void (and Famed Mimic Gogo mimed this ability, allowing him/her/it to go into the FFVI world). Then, he went looking for Excalibur in the FFII world after the Emperor was defeated, but he couldn't find it because Firion and co. already took it from Ricard's widow. So instead, he brought his kid, Kain and Leon to the FFIV world and dropped them off there, which makes sense because the FFII Kain said he wanted to become a Dragoon, and the King of Fabul said that Deathbringer was left there by a Dark Knight named Leonhart.

The Espers (or Phantom Beasts) in Final Fantasy VI are the same entities as the summons from nearly every other Final Fantasy game, and FFVI is their origin story.
Rather than dying at the end, they are reborn in the Esper World, able to live as magical creatures without messing up their original homeworld. Over centuries, they learn to extend their perceptions into other worlds and increase their powers until they become almost godlike; they devote themselves to aiding those who fight evil in those other worlds, offering their powers as Summoned Beasts to heroes. (Why do the summons work differently in different games? Different rules of magic in each world limit their ability to manifest.)
 * Or, they did die, and were reborn on Spira as humans... in Zanarkand. And then proceeded to become Aeons. After death in the ending, they came back via materia from the Lifestream in FF7, keeping summon-form because they technically didn't reincarnate. After being summoned enough times there, they gained enough power (MP) to exist independant of a summoner, then left for the Summon Realm to help out the other various worlds.
 * From now on, every time I read the words Everyone Is Jesus in Purgatory I shall be mentally replacing it with Everyone Is A Human In Zanarkand.

Bahamut is the Zenith Dragon/Divine Dragon and Shinryuu/Lord Dragon is the Grand Dragon.
The Square-Enix fusion fused the Crossover Cosmology as well. Zenith Bahamut has tried setting up up a society from time to time in different worlds; dragons, Eidolons, Zenithians, etc. He's a tad xenophobic, but ultimately a good guy. Lord Grand Dragon mostly tests heroes in the Bonus Dungeon, but he did help Cid of the Lufaine in Dissidia Final Fantasy.

All Final Fantasy games take place on the same world, at different times.
Same races, similar magic This is easy enough to support, since any landmass-shifting can be explained by the various catastrophes that befall the world each and every game. To be honest, this can also explain why nobody remembers the events of other games, since they either descended into myth or the Gotterdammerung smashed humanity to bedrock (Meteor/Holy in FF 7 being the best example i can think of) Notably, in FFX-2, one character theorizes about using the planet's soul energy for power... which was the theme of the first half of FF 7. Different methods of using magic are cause either by evolving traditons and refinement, or from previous knowledge being lost the same way knowledge of the other games is.
 * Dissidia Final Fantasy appeared to actually confirm this in the first trailer, all but confirming that the abnormal events of bringing together heroes and villains from the first ten incarnations of the world in this game is essentially Chaos trying to stop the cycle between the twelfth and thirteenth incarnations, and Cosmos being forced to act abnormally to continue it. Speaking of which...
 * Further corroborated by the fact that Squall Leonheart seems to have descended from Leonheart of FF 2, and a book in FF 8 even seems to reference FF 2's storyline.
 * The vast differences in advancement of civilization (the early games have kingdoms and empires, whilst 7 and 8 have countries with corporations or modern civil governments as did Zanarkand-age 10, and 12 seems to be somewhere in the Renaissance) and technology (no tech except the very rare airships in everything up to 5, Magitek in 6, full tech in 7 and 8, back to medieval in 9, full tech in Zanarkand knocked back to dark ages by Sin in 10, and back to tech again in 12) can be explained by having the timeline of FF on a wave curve of advancement versus decay - when the curve is going up, civilization is advancing - populations are growing, countries modernize, tech advances, etc. - then it reaches a peak and hits a downward slope of decay - tech fades into uselessness or begins having Dark Tower-esque dysfunctions, modern civilizations degrade back into feudal system, and so on. (This is, of course, assuming the games were released in chronological order.)
 * Combining this with a slight re-interpretation of the "Trapped in the Time Loop"/Dissidia theory, we could also say that there is truly only one major villain in the FF universe - Garland, constantly being reincarnated:
 * FF1: The Fiends turn Garland into Chaos. The Light Warriors slay him, Time Loop, presumably there's some sort of temporal crash eventually. Garland's soul, empowered by becoming Chaos, haunts the earth.
 * FF2: Garland either reincarnates as Emperor Palamecia, or possesses him. Killed by Firion's group, attempts an immediate reincarnation (Light Emperor), but the quick action of some already-dead heroes prevents that.
 * FF3: The Imbalance. Whenever the forces of Light or Darkness get out of balance, Garland siezes the opportunity and manifests through them. He did it once before as an Incarnate of Light and was beaten, tries again this time around as Cloud of Darkness and fails again.
 * FF4: The Lunarians are presumably a peaceful species, Zemus being the only exception - we can chalk that up to Garland's influence. Drives Zemus into a hate-fed rage over many years, so powerful that when Zemus is killed Garland can harness that energy to forge himself a new body - poof, Zeromus.
 * FF5: Reincarnates as Enuo. Gains power, masters Void Magic... gets himself killed. Before he can attempt a new plan his soul gets bound to a tree, so he starts messing around with that and eventually merges with it, creating ExDeath. Manipulates events to get himself free, tries to go after more power with the Void... ends up overestimating his own abilities in this form and screws up, hence NeoExDeath. Killing him resets the cycle, back at square one.
 * FF6: Reincarnates as Kefka, but without knowledge of who he is or what his purpose is - perhaps a side effect of the NeoExDeath screwup. Goes through life fairly normally, though there are slight hints of his evil potential, as he signs up for the military and ends up becoming an officer. Volunteers for the Magitek project, which breaks his psychosis and partially revives the Garland personality, but now twisted with insanity. This time around he finally gets what he wants, and nigh well obliterates everything, but gets killed off before he can finish the job.
 * FF7: I'm partial to the Jenova is the Real Villain theory myself, and personally I think she makes more sense in this line of thought. Comes to earth, screws with the Cetra, gets sealed away rather than killed. Found and used for experiments, Sephiroth gets created, giving Jenova a perfect puppet. She mentally manipulates Sephy into doing all the stuff he does through the game. Decides to challenge the heroes herself finally at the end, first alone (Jenova Synthesis), then tag-team fused with Sephiroth (Bizarro - tell me I'm not the only one that sees the second head on Bizarro looks female, suggesting a woman hanging with her arms around Seph's neck and shoulders). When that fails Jenova/Garland is dead, sending the soul back to prepare for another reincarnation, but s/he gives Seph the rest of their power, hoping he can finish the job, and of course he doesn't. AC on the other hand was out of Garland's control - that was Seph/Seph's clones trying to do things on their own and failing miserably.
 * FF8: Garland decides to try the mind-control/possession route again. Notice how all the sorceresses go berserk after a while? That's Garland messing with their brains. Unfortunately his control isn't as precise this time around, especially after Ultimecia tries that crazy "Time Compression" trick. Let's not try that plan again.
 * FF9: Reincarnation isn't working. Mind control isn't working. Let's try Chessmaster. Garland (the FF1 one, not the one from this game, of course) decides to sit back and influence the world indirectly, rather than deliberately controlling things. Kuja, the rejected prototype? Let's encourage those feelings of overconfidence and, later, worthlessness and desperation. A magic crystal that controls life? Let's influence him to blow it up! When that fails to kill the heroes and obliterate the world, hey, Kuja just destroyed a Cosmic Keystone of life energy! Garland takes advantage of all that stray unused energy and incarnates again as Necron. Fails again.
 * FF10: This time Garland decides to combine reincarnation with a little bit of civil manipulation. Incarnates as Yu Yevon, who turns himself into Sin. His body can only be destroyed by a really powerful Aeon, and when it does he just possesses that and turns it into a new Sin, yay eternal reincarnation! Furthermore, let's convince the whole world it's their fault Sin's here, so the only way to get rid of it is to keep killing it, fueling the cycle. Then someone got tired of that plan and decided to make someone who wouldn't play by the rules. You think by now, you'd have expected something like that, Garland...
 * FF12: This is the one, at least for me, that doesn't seem to fit in this theory. Neither Vayne nor Venat really has the kind of mentality that most of the former FF villains had by endgame. Thoughts?
 * Garland/Chaos is Ivalice (the world, not the country). That's why so many major adventures happen there. Alternately, he just hasn't shown up yet, and when he does it will link all the previous ivalice stories.
 * No, neither Vayne nor Venat were really fitting with Chaos' ideals; the other Occuria are. Meaning that you are actually the bad guys. This seems to be a trend with Ivalice games.
 * Mayhaps Garland/Chaos has had little to do with Ivalice. Perhaps all the reincarnating in Final Fantasy X drained most of his power so he was only able to affect the events in XII very little, such as starting the war. Perhaps he had some sort of plan to regain power and so was manipulating things until the heroes killed Vayne Solidor/Vayne Novus/The Undying and brought peace.
 * So where does XIII stand on that then?
 * Well, maybe Pulse is the same planet from FFVII a long time after it went all natural, and Garland was the Maker that created the fal'Cie. Hell, the some of the fal'Cie apparently try to bring back the Maker which could've been Garland's plan to be resurrected again.
 * Jossed by Word of God, FFX takes place in the same universe as FFVII, but on another planet and at an earlier point in time, so earlier in fact, that the boy Shinra in X-2 is not just a Shout-Out, but the ancestor of all humans on Gaia after the Cetra.
 * Maybe not. Perhaps all the games don't take place on the same world but rather in the same universe. Additionally each game might not be in chronological order so the theory could still work.

Chaos is fighting in Dissidia to protect the twelfth incarnation of the world in Dissidia and Cosmos wants to destroy it so she can create the thirteenth incarnation
Cosmos is in fact the creator goddess in the fictional mythology of Final Fantasy XIII, while Chaos is very much the god of the first twelve worlds. The crystals are key because they are required to create the thirteenth world, but this can only happen by destroying the previous one, being Ivalice of Final Fantasy XII.
 * Jossed by duodecim, since Cosmos lost the war (though it was already implied in the original Dissidia)

All Final Fantasy games take place in the same universe, but on different worlds.
A statement by series creator Hironobu Sakaguchi confirms that the descendants of Shinra from Final Fantasy X-2 eventually developed space travel, left Spira, and colonized Gaia, the world of Final Fantasy VII, becoming the ancestors of the humans who.

All Final Fantasy games take place in Final Fantasy I's Stable Time Loop.
Each time the world is reset, the geography changes and 2000 years of history play out differently. The Four Fiends and the Big Bad are reincarnated in different forms, and the heroes never discover the time gate, instead destroying the latest incarnation of the Temple of Chaos and unwittingly dooming their continuity. This, naturally, puts The Final Fantasy at the very end of the series. And turns the rest of the series into a Shoot the Shaggy Dog story.

Cid Highwind is a descendant of FFIV's Kain.
Let us count the similarities: blonde hair, uses polearms, last name Highwind... at the end of FFIV, Cecil and Rosa live happily ever, while Kain and Rydia strike out on their own... or do they? Add in the fact that they have a space-travel-capable ship, and it's entirely possible that they got together and emigrated to a new world, hoping to start a new life (and a family) there.
 * Jossed by After Years.

Gilgamesh is the true master behind everything that's taken place in the entire series.
That's why he isn't in Dissidia: he's busy pulling the strings of all the characters behind the scenes.
 * B-but he WAS a Summon in Dissidia...
 * And he's in the sequel...

Final Fantasy - universe was originally created without any magic and the majority of people didn't have magical powers before Final Fantasy seven
FF world didn't have the magic to begin with, but its creator held all the magic within himself/herself. He/She created powerful, magic-wielding avatars called Espers that were able to teach magic to certain men or women who had the "magic gene" and needed it to save the world. Ability to wield magic was bestowed upon few, selected people.

However, between Final Fantasy VI and Final Fantasy VII'', something went wrong. People who had the "magic gene" married each other, maybe even formed societies, and the gene spread like a cancer, becoming essential part of the people's DNA. This allowed anyone to train themselves as mages/summoners/etc if they wanted to do so.
 * This mystifies me as FF III, FF IV, and FF V held summons, maybe they all left the normal world for fear of their use and that adds to the events of FF VI, then they return as summons and teach magic (as Espers) which ANYONE can use. . I think this would become the new Materia for FF VII

Kupo is a swear word.
All the moogles are really foul-mouthed and know they can get away with Cluster F-Bombing everyone they meet because it sounds cute to them.

When all the Hum(ans)e, Bangaa, Veira, Mithra, annoying hobbits from FFXI, yeti, etc leave the room the moogles belittle them for their lack of pom-poms.

Moogles are dicks.

Kupo actually means "Shit" In polish.

Chocobos evolved from Yoshies.
Hey, if chickens evolved from dinosaurs...

Balthier is Immortal
As shown in the ending of Final Fantasy XII, he's the Leading Man, and he can never die. This is explains why he's in Final Fantasy Tactics, thousands of years into the future, because he never died. He even mentions that he misses Airships, since that era is without them. At the end of the game, Ramza and everybody might have died, but Balthier definitely lived. Fran's immortal too, but she's hiding someplace. A corollary of this is a proof that Vaan is actually imaginary since he shows up in Final Fantasy Tactics A2, which takes place in a dream storybook Ivalice.
 * Except that Word of God says Final Fantasy Tactics A2 takes place in the real (real as a fictional video game setting can be) Ivalice.
 * Also...

Balthier is a Time Lord.
What. Someone had to say it.

The True Origin of Tonberries...
...is that they were spawned by an unholy union between Kermit the Frog, and Satan. We can only assume that quite a bit of alcohol was involved.

All the games are dying dreams of the main characters.
Why else would they be named Final Fantasy?
 * Artifact Title because the original game was supposed to be Hironobu Sakaguchi's last game. It could also refer to the fact that the Warriors of Light in the first game end a Stable Time Loop, making it the final iteration of a fantasy. This could, by extension, be applied to some of the other games. Final Fantasy VIII also features a Stable Time Loop (sort of) and Final Fantasy X features the final pilgrimage to defeat Sin.
 * There is one theory for FFVIII. Who will dare to come up with a theory for every game?

The Crystals are actually Huge Materia.
Crystals are actually nothing more then highly condensed Mako, and thats also why they can teach abilitys via class changes.
 * Possibly Jossed by Final Fantasy IV: The After Years, where it's established that the crystals are magical terraforming agents sent by The Creator; its extremely doubtful that Materia, no matter how big, could actively make a planet more earthlike by mere presence with no active user.
 * Though that's only true for the FFIV Universe. The Crystals play different roles and have separate makers in each version.
 * Its heavily implied to also be true in I and V, given that the effects of the loss of the crystals in both of those games is entirely consistent with the loss of Cosmic Keystone terraforming agents. "The wind stops, the sea is wild, the Earth begins to rot", etc. Even if they weren't sent by The Creator, they're still terraforming agents that operate independent of human users, whereas most Materia is inert and inactive without users after leaving the Lifestream. Plus, since materia is a product of the lifestream, not the lifestream itself, the fact that loss of a Crystal has major environmental effects shows that they're much more important, cosmologically, than materia; for a similar effect using materia, you'd have to destroy the Lifestream itself.

The Blue Planet is Pern
In FF1, it's pretty obviously post-apocalyptic in that there's a space station in orbit that can be reached by a teleporter from a space-age skyscraper. And one of the dragons tells you there was once a time when humans and dragons lived together. FF4 confirms that the Crystals are terraforming devices placed by a Precursor, and FF9 confirms that Black Mages are automatons designed as weapons. Here's what went down.

Late in Pern's history, medical and military science achieved "soft" SF levels; phasers, medical tricorders, etc. The only caveat was that the correct device needed be used for the correct ailment; a detoxifier wouldn't close a wound, neither would an ocular surgical laser purge poison, or an energy-suture heal blindness. Military robots were constructed, though primarily used commercially as security forces, with only a select few being equipped with superpowered weapons. Power sources were all The Pernian human race launched a massive military satellite, codenamed "Sky Fortress", to do away with this "thread" bullshit once and for all. They destroyed the Red Star, resulting in the unholy mother of all Threadfalls. Dragons and humans both were subsequently driven to near-extinction. In-development bioweapons, part of "Project Eidolon", broke free, some of them truly horrific in nature, such as "Lich", a project to extend human lifespan with nanotechnology that instead ended in Body Horror. The robots became self-aware, concealing their nature from other creatures with dark robes and ridiculous hats. Because of the highly destructive and mysterious nature of their equipment, and their dark robes, they became known as "Black Wizards". A cult also sprung up around the healing tech; the "priests" became known as "White Wizards". Later on, some humans learned how to operate equipment from defunct Black Wizards, furthering the confusion. In any case, this is the reason spells are bought the way they are. The reason some individuals, IE Terra or most of the FF4 cast, can cast spells naturally is due to descent from an Esper or Eidolon.

Every game takes place in an alternate universe version of the same world.

 * And some of the characters are recurring.
 * Cloud is Lightning
 * Yuffie is Rikku
 * Cid Highwind is Cid Highwind

tl;dr Final Fantasy is really Final Softsciencefiction; all the magic is sufficiently advanced technology and all the weird critters are bioengineering projects that went wrong or were left half-finished.

All of the games are actually a look at the thoughts of one man.
Came up with this recently. All of the games aren't actual events happening in different universes; they are all the thoughts of the storymaker who made up these fantasies. His first work was a simple "save the world" plot, but as he progressed through his life he added more and more elements into his stories. The main series are his main tales, the spinoffs are his other works.

Either Final Fantasy XV or XVI will go the Mega Man 9 route

 * What I mean, is that it will be a downloadable 2D game to please the old school fans. It will have 16-Bit graphics, PS 1-style FM Vs, and the occasional voice acting.
 * With the 25th Anniversury of the franchise being next year, I'm sure they'll have something for us. Maybe not a game in the main series, but a spin-off following the classic style.
 * Wasn't the game "The four heroes of light" supposed to be that ?

Every game is a retelling of the same story
Like The Legend of Zelda theory that every game in the franchise is the same story being retold by a different person, there is one legend of a group of heroes going on a quest to save the world from a great evil, probably involving crystals and chocobos and moogles etc., passed down through the ages, adapted and distilled and so on.
 * Final Fantasy I is the most stripped-down, bare-bones version of the story, probably its initial inception in medieval times or a summary on Wikipedia.
 * Final Fantasy VII is told circa the 80's, between schoolkids or written down in novel form.
 * Dissidia is fan-fiction. Even moreso than it is now.

Every game takes place in the same universe, but…
While some instances are on the same planet (thinking of II and IV with their many connections), the fact that it's told as a legend means that nothing is reliable. So for instance, the map we see in just like a map of our world in the Medieval times : strongly incorrect. All inconsistencies can be explained the same way : being legends, time has changed them beyond recognition.

There are actually two species of Moogle.
One species, featured heavily in Final Fantasy XII, have a more detailed, animalistic face and clothing and are the base species of Moogle/moguri. The more cartoonish, teddy-bear-faced mogs/moogles/Moguri with no clothes (easily seen in Kingdom Hearts) are related or arose by parallel evolution, and should more properly be called naked mole-bats.

Gilgamesh is secretly Bender in disguise, with some amnesia.

 * First of all, this is Self-explanatory since his appearance in Final Fantasy XII, but John Dimaggio's absence as of Final Fantasy Dissidia perplexes me. Now, onto business - the main reason he's here in the first place because Ex Death was the one to summon him first as an indestructible henchman. One bump in the continuum later, Bender loses his memories on his way, and Ex Death dubs him something or other. (To be continued)

David Bowie is Chaos.
If you look at several of the villains of the Final Fantasy games, you may notice at least a passing resemblance to David Bowie (see Emporer Mateus, Kefka, and Kuja). Even Ultimecia looks a fair deal like Bowie in a good amount of makeup. Combined with the fact that Chaos could be every villain, logically David Bowie and Chaos are, in fact, the same being. As a side note, also consider that David Bowie is the shapeshifting sovereign of all villainy.

The FF-Verse is split into two distinct continuities which both begin from Final Fantasy I.
Final Fantasy I sets everything up. It's a world where magic is predominant over technology, but it is clear that technology was dominant earlier in the world's history. From there:
 * In the first continuity, once the Stable Time Loop is resolved, someone finds the airship that the Warriors of Light discovered and uses it to finally get to the northern continent, where he finds Lufenia and discovers more technology that they used. From there, technology became predominant, leading to Final Fantasy VI, which led to Final Fantasy X, which led to Final Fantasy VIII, Final Fantasy VII, which led to Final Fantasy XIII, where Pulse is the Planet from FFVII and Fal'cie are the Lifestream after having millions of years to change and eventually take on multiple physical forms, which later became independent beings that formed factions, one that built Cocoon and another that stayed on Pulse. Since the events of FFVII, Materia have returned to the Lifestream and manifested in XIII as the Crystarium and l'Cie sigils.
 * In the other continuity, the airship is destroyed or stops working before anyone finds it and the story continues with magic as the dominant force. This leads to FFII, to III, IV, V, IX, and XII. XI and XIV are not canon due their being Multiplayer nature.