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Pointless trivia about Final Fantasy. Mostly VII, IX and X.

Final Fantasy X originally didn't begin as a Final Fantasy game at all. The initial concept was for an independent game called Seventeen, a science fiction game about a virus that kills people on their 18th birthday. The main character, a doctor/priestess, travels the world handing out vaccines for the disease under the employ of a pharmaceutical company/cult. It would later be revealed that the vaccines were actually causing the disease, and the company was using this to control the population. When the plot was reworked into a Final Fantasy game, the virus was changed to a monster, the pharmaceutical company was changed to a corrupt church and the doctor/priestess was changed to a summoner on a religious pilgrimage.

Tidus's Japanese name is Tida, which in the Ainu language means "sun". Yuna's name means "moon" and Wakka's name means "water". This is why Tidus and Yuna's Celestial Weapons are powered with the Sun Crest/Sigil and Moon Crest/Sigil respectively.

In beta versions, Tidus had dark/black hair, but it was changed to blond in the final product to emphasise his connection to the sun.

It's a point of contention among fans over whether Tidus should be pronounced "Tee-dus" or "Tie-dus". Given his original name is Tida, pronounced "Tee-da", "Tee-dus" is closer to the original pronunciation at least, and James Arnold Taylor, his English voice actor, has said he prefers that pronunciation. When Square Enix hired an English speaker to narrate a Japanese advert for the game, the narrator pronounced it as "Tee-dus", and Square Enix adopted that as the official pronunciation for future Final Fantasy games such as Dissidia. In Kingdom Hearts, Wakka pronounces it "Tee-dus", but in Kingdom Hearts II, Selphie pronounces it "Tie-dus". Those who argue for "Tie-dus" say that it sounds like "tide-us", as in "tides", and the character has a very strong thematic connection to water. Also, Yuna's name means "moon", and what's affected by the moon? The tides.

James Arnold Taylor gave the reason for the rather high-pitched, whiny voice he gives Tidus, especially early on, as that Tidus was presented to him as an angst-ridden, somewhat spoiled teenager who never had to do much but enjoy the cheers from the fans until he's thrown into a whole different world which changes him. This is why his "narrator" voice is more controlled.

An interview in an issue of Ultimania suggests that Final Fantasy VII is the distant future of Final Fantasy X's world, but likely on another planet.

Tidus was originally going to be revealed to be an Unsent, but Nomura watched The Sixth Sense (which has the same kind of twist) and realised the game might be seen as a ripoff of the movie, so he moved the reveal to Auron instead.

The game contains data for a "Buster Sword" weapon for Tidus, which can be put back into the game via hacking and does indeed resemble Cloud's Buster Sword from Final Fantasy VII. It's unknown whether this was actually intended to be in the final game or just put in as a joke by the developers during beta testing, but what's interesting is that when Tidus swings the Buster Sword, he swings it blunt edge first, just like Angeal (the original owner of the Buster Sword) in Crisis Core: Final Fantasy VII.

Kimahri's Celestial Weapon is named Longinus in Japan, the name given in Christian mythology to an unnamed Roman soldier who pierced Jesus's side with a spear while he was being crucified. In modern media, it's often used as the name for a legendary spear. For whatever reason (possibly wanting to avoid religious references), the English localisation team changed the name to Spirit Lance.

In Final Fantasy IX, the Nova Dragon enemy is a reference to the optional superboss Shinryu from Final Fantasy V. The name "Shinryu" can translate from Japanese as "Holy Dragon" or "New Dragon", and "Nova" is Latin for "New".

Final Fantasy IX was intended as a celebration of the franchise and a "return to roots" of sort for it, which is why it contains many, many references to earlier Final Fantasy games. Off the top of my head:

• Freya's weapon, Kain's Lance, refers to Kain Highwind, a Dragoon from FFIV.
• Mount Gulug is a reference to Gurgu Volcano from FFI (the katakana is "Gurugu" in both cases).
• The bells in Gizamaluke's Grotto are references to the Goddess Bell from FFII.
• When Garnet finds Ramuh, he asks her to assemble pieces of a story. The story he tells is actually about Josef, a minor character in FFII.
• The items Une's Mirror and Doga's Artifact are references to Unne and Dorga, characters in FFIII. When you have both in your inventory and examine the gramophone in Black Mage Village, it plays "Dorga and Unei's Theme" from that game.
• The Black Mages of Black Mage Village name their baby chocobo Bobby Corwen. The first syllables of both names make Boco, which was the name of Bartz's chocobo in FFV.
• Eiko's favourite Moogle is named Mog, the same name as the Moogle party member in FFVI.
• Madeen is a reference to Maduin from FFVI.
• The powered-up form being called Trance is also a reference to FFVI, though the initial English translation called it Morph.
• One of Amarant's attacks is called No Mercy, the same name as Seifer's Limit Break in FFVIII.
• Zidane's Trance skills are called Dyne, the name of Barret's brother in FFVII (this was added in translation - in Japan, the skills are called Urawaza, which roughly means "sneaky/underhanded tactics").
• Each character behaves like a class from the previous games (Zidane is a Thief, Vivi is a Black Mage, Garnet is a Summoner/White Mage hybrid leaning more towards the Summoner side, Steiner is a Knight, Quina is a Blue Mage, Eiko is a White Mage/Summoner leaning more towards the White Mage side, Freya is a Dragoon/Dragon Knight and Amarant is a Monk/Ninja hybrid). When you first have a full party in the game, it consists of Zidane, Steiner, Vivi and Garnet - in other words, Fighter, Thief, Black Mage and White Mage, the default party in FFI.
• Garnet's real name is Sara, referencing Princess Sarah from FFI. Her real mother's name is Jane, referencing Queen Jayne from the same game.
• Freya's skil Reis's Wind references Reis Duellar from Final Fantasy Tactics, whose skills revolved around dragons.
• Steiner's skill Shock has the same name as one of Leo's skills from FFVI, and his Climhazzard move shares a name with one of Cloud's Limit Breaks from FFVII.
• The Blood Sword is a reference to the same weapon from FFII, and functions in the same way.
• The elemental shrines and the guardians within are one huge throwback to FFI, specifically the Four Fiends and their temples. The fiends even share names, though Marilith is mistranslated as Maliris (this boss was called Kary in the first English translation of FFI due to space limitations).
• The boss Hilgigars is a reference to Hill Gigas, an enemy from FFI (called GIANT in the NES translation).
• The potions you find in order to attempt to change Regent Cid back to a human have quotes from someone called Matoya when examined in the inventory, referencing the witch Matoya from FFI.
• Summoners having horns is a reference to the Summoner class's debut in FFIV, where all Summoners had horns. This is given another nod in FFX, where the Ronso (for whom horns are kind of a big deal) promise to build a statue of Summoner Yuna, "with grand horn on head".
• Castle Alexandria's true identity is the summon Alexander, which first appeared in FFVI. 
• Kuja being motivated by fear of his own mortality is similar to Xande from FFIII.
• Garland's job being to ferry souls from a dying world to a living world is similar to Fusoya from FFIV.
• The two planets, Gaia and Terra, being blue and red respectively is a reference to the two moons in FFIV, the Red Moon and the True Moon.
• In Oeilvert, the talking faces describe various airships from history as technology evolved. They're actually describing and showing the Sky Warriors' Airship from FFI and the Dreadnought from FFII.
• The cry of the dwarves in Conde Petie, "Rally-ho!" is a corruption of the "Lali-ho!" cry that the dwarves in The Dwarves' Castle in FFIV use.
• Cloud's Buster Sword can be spotted on the wall of the weapon shop in Lindblum. Examining it will make Zidane comment "I remember a guy with spiky hair who carried something like this", referencing Cloud himself.
• In the play at the end, Zidane says "No cloud, no squall shall hinder us!", an obvious reference to Cloud Strife and Squall Leonhart, the protagonists of FFVII and FFVIII respectively.
• The same play has a character named Princess Cornelia, a reference to the city Coneria in FFI.
• The first FF also had a villain named Garland.
• The item Pumice, used to summon Ark, is named Fuyuuishi in Japanese, which translates as "floating stone". This is the same name as the Levistone item from FFI, also known as FLOATER in the NES version, which was used to summon the Sky Warriors' Airship. The Eidolon Ark resembles an airship, furthering the connection.