The Warrior of Light's Fire, Ice, Lightning "Fang" magic attacks are named after the items that cast elemental magic that were added in the remakes. If you look closely when he attacks with them, you can see he's actually throwing an item into the air, not casting the spell himself.
If you look even closer, he's pulling the items from the pouch on his left hip.
The Warrior of Light's Victory Pose when confronting Garland and ending his EX Burst mirrors the original artwork of the Knight.
When you find the Bahamut summon in the Warrior's storyline in Dissidia 012, Bahamut says "Long has it been since men of courage have stood before me", the same thing he said when granting you your Prestige Class in the first game.
Garland's sword has five forms, and aside from the base greatsword, each form references one of the Four Fiends and their elemental attack that Chaos is able to use in the final battle of the original game — the whip is used when casting Tsunami (Kraken), the twin swords are used for Blaze (Marilith), the Lance is used for Tornado (Tiamat), and the axe is used for Earthquake (Lich). His Flare attack in 012 retains the base greatsword form, reflecting that Flare is Non-Elemental.
Garland is fought as the first and last boss of the Warrior's story, just as in Final Fantasy (okay, he transformed into Chaos for that last battle, but still).
When taunting the Warrior of Light, Garland's line "You will meet your end here, and I will live forever!" is a paraphrase of what Chaos says before the final battle.
When unlocking Garland through the PP Catalog, he will shout "I will twist you into a knot!', which was an actual threat used by Garland in the original Final Fantasy.
Firion's fighting style reflects the entire battle system and the different weapon types — swords, bows, lances, daggers, axes, staffs, shields, and barehanded. In fact, pretty much the only thing you can do in this game that you couldn't do in Firion's original game note that isn't only different because of the gameplay style is shoot your other weapons out of your bow.
Firion's knives are charged with electricity. Leila, the character who fought with knives in the game, joined the party with the Thunder spell.
Whenever Firion fires an arrow, the bow flips forward, the same animation for bows in the original game.
Firion's interactions with Shiva are an impossible-to-miss reference to his seduction by the Lamia Queen. The poor guy will Never Live It Down.
Firion has a trademark pose, appearing in the most well-known concept art of him as well as the original Famicom boxart of II—he holds his arm out, sword horizontal in front of his face. This appears twice in Dissidia — in a cutscene, from the same angle, right before he fights The Emperor, and as the very end of his match-start animation, before he sheaths the sword, though this one is harder to notice due to the angle of viewing being different than the art piece.
The Emperor's Shock and Awe spells refer to the fact that his only offense when fought in human form in the original game was a Thunder X spell.
The Onion Knight's swords take their appearance from the concept art of the Unnamed Warrior. His pose when finishing his Ninja EX Burst is, you guessed it, also from concept art.
Open up the other menus during his EX Burst — every other item, spell, and weapon you see is something from the original game.
Both his EX Bursts copy the style of battles in the original game, right down to him taking a step forward when his "turn" is up.
When using her EX Burst, and in the Onion Knight's EX Burst, the Cloud of Darkness poses in the same way as her original sprite was positioned. Particularly notable for her, since all other characters just use their "idle" poses when Onion Knight uses his EX Burst on them.
The Shadow Dragon's Black Fang and Binding Cold attacks are taken from the boss battle with Golbez. Twin Meteor (see directly below) is his Combination Attack with Fusoya.
If the inputs for Golbez's EX Burst are performed at very specific frames, his Shadow Dragon will shout (via text box) "Give your power to Meteor!" to which Golbez will reply with "Very well!" ("Iidesutomo!" in the Japanese version) in reference to his and Fusoya's battle against Zemus, as well as a popular meme in the Japanese FF community.
Golbez randomly says "Allow me to give you something" when using Gravity Force, and says "A gift!" when using Gravity System and Float System — when he met Cecil at Fabul, Golbez said "Allow me to give you something - a gift to remember our meeting by."
Golbez's Cosmic Ray is based on his cutscene attack where he knocks party members aside with lightning blasts from his hand.
When someone other than Cecil beats Golbez in Shade Impulse, he says "The flesh may rot, but the soul never perishes...", which is what Zemus said when Golbez and Fusoya killed him.
Kain's Spiral Blow and Sky Rave attacks are Band skills from The After Years.
Kain's EX Burst quote, "Let me ease your pain", is what he says when preparing to kill Cecil at Fabul. Well, to be specific, it's "let me ease your suffering", but same idea.
The pose Kain has when at the end of his successful EX Burst is the same pose he is seen holding on the game's original logo.
The Onion Knight asks Kain "Can you catch birds with that jump?", serving as two references — Kain's DS minigame where players had to swat away birds as he leapt into the air, and the Garuda from III, widely considered That One Boss unless you spammed the Dragoon's Jump attack.
When starting his EX Burst, Exdeath briefly adopts a pose similar to his second, monstrous tree form. Exdeath also has a hidden second voice clip for his EX Burst obtainable after he's reached Level 100 where he furiouslyshouts "TURTLE!" (or "KAME!" in Japanese) at random when initiating the attack — just as he does when the sage Ghido, a turtle, interferes with Exdeath's plans in FFV.
The name of his EX Burst in the original Dissidia (The laws of the universe mean nothing!) is taken from the text accompanying Neo Exdeath's use of Grand Cross (which Exdeath himself can use both as a standalone HP Attack and to close out his EX Burst if the player flubs the input), likely included as nod to that description's memetic popularity among the Japanese fandom.
"Ebony Robe", Exdeath's second alternate costume in 012, unmasks Exdeath to reveal the snarling demonic face of the horned humanoid entity seen at the front of the mass of bodies comprising Neo Exdeath.
Gilgamesh's weapon arsenal is made up of weapons he has or could have collected — the Excalibur, Excalipoor, Masamune, and Zantetsuken are his summon attacks in Final Fantasy VIII, the Chicken Knife was in his original game (and there's more to that) The player can only get the Brave Blade or the Chicken Knife; the other is permanently missable. Since apparently Bartz took the Brave Blade, that left the Chicken Knife behind and presumably Gilgamesh got ahold of it somehow, the Genji Katana of course refers to his trademark Genji equipment, and the Naginata and Battle Axe are weapons his sprites are holding.
The Genji Katana specifically takes its appearance from Auron's Genji Katana. A bit of Fridge Logic there, since we never see Gilgamesh visit Spira, but apparently he got there somewhere along the way.
His taunt when using Jump, "Fell for it!", is a joke on how Gilgamesh likes to pretend the party has beaten him during your various encounters throughout V, only to cast status buffs on himself and use a Jump attack.
The Data Install screen for the original Dissidia references the opening to FFV, showing Bartz running through the fields on his Chocobo.
The job cards of the Duel Colosseum and Labyrinth are based on the game's Job System, the latter having every job class from the game aside from the Game Boy Advance-exclusive jobs. The abilities are based off an ability the job teaches in V, and the images on the cards are based off of the appearance of the job in this game (more noticeable with jobs with inconsistent looks, like the Blue Mage and Chemist).
Aside from Flood and Thundara, all of Terra's attacks are spells she or Celes could learn naturally.
Terra's EX Mode bonus description reads that she "embraces the spirit of a magus" — in the original game, the Dualcast ability was attached to the Soul of Thamasa accessory.
At the end of the Onion Knight's story, Terra (who was forcibly transformed into an Esper and attacked him earlier in the story) is lying unconscious, and a concerned Onion Knight has Terra's situation explained to him by Golbez. Golbez tells him that Terra is afraid of what she is, and that she needs some time to come to terms with her situation. The whole setup is very similar to the visit to Zozo, after Terra transforms when speaking with the Frozen Esper. The leader of the playable party is approximated by the Onion Knight, and Golbez takes the place of Ramuh.
Terra's Crystal has a shape similar to a Magicite crystal.
In 012, Terra says she feels nostalgic looking at the snowfields, a reference to Narshe.
The unique accessory Terra wears when Kefka controls her is the Puppeteer's Wheel, a mistranslation of the Slave Crown she wore in the original game.
Her relationship with Vaan and Onion Knight in both games is a collective reference to Locke.
All of Kefka's attacks are attacks he uses in the final battle, though his Fire, Ice, Lightning spells are given wacky twists.
The pose Kefka takes on at the end of his (imperfect) EX Burst is the same one he had at the final battle of the original game.
Many of Kefka's one-liners from the original game made it in:
"Don't think you've won this!" and "Graaah! I'll remember this!" are from his defeat at Narshe.
When facing the Emperor, he says "You're less than worthless!", based on what he says when he kills Gestahl. His Extra-Crispy Firaga quote "You'll be well-done!" is taken from the same scene.
"You're lower than lower than dirt!" and "That hag isn't worth the dirt on the bottom of my boots!" paraphrase his taunt to the party, "You may as well be the dirt on the bottom of my boots! Or the dirt stuck to the bottom of that dirt!"
When Lightning tells him and the other Warriors of Chaos to step aside, Kefka replies "'Step aside' she says. Do we look like side steppers?" When he ran from his battles with Sabin, Sabin called out "Wait!", and Kefka's response was "'Wait' he says. Do I look like a waiter?"
When preparing to fight Vaan, he says "You're about to learn why 'oppose' rhymes with 'dispose'!", the same thing he said to encourage his troops when he attacked Narshe.
Pretty much all of his dialogue in the final storyline is taken from his pre-final battle speech in the original game.
When Kefka begins his EX Burst, three colored circles appear over him: blue at the top, yellow on the left, and red on the right. The Warring Triad, the gods he absorbed his power from, are in the same positions atop the Floating Continent — the blue-clothed Goddess was at the top, the red Demon was at the right, and the yellow-winged Fiend was at the left.
Kefka catches Kuja planning to sneak Zidane and his friends behind enemy lines and interrupts them, claiming it was Kuja's plan to lead them there and betray them all along. He pulled the exact same stunt on Celes and Locke in the Magitek Research Facility.
He pulls a similar stunt with Terra and the Onion Knight, telling them how Terra attacked the Onion Knight. The twist being that he's actually telling Terra this, as the Onion Knight already knows, and Terra lost her memory of the event.
The Data Install screen for Dissidia 012 references the opening to FFVI, showing Terra and two soldiers treking through the snow in Magitek Armors.
The camera angles in Cloud's confrontation with Sephiroth mirror many of their battles in other entries of the Compilation of Final Fantasy VII — see here◊ for a comparison.
The speed of the scene changes and the accompanying sound effects during the cutscene fight between Cloud and Sephiroth are similar to Advent Children, whenever Sephiroth's influence shows itself.
When Cloud returns to his world at the end of Dissidia, he's seen in a field of yellow flowers. This is the scenery used when he thinks of Aerith in Final Fantasy VII: Advent Children.
The "Allure of Honey" equipment set refers to the infamous Wall Market cross-dressing scene — the Sexy Colonge, Member's Card, Blonde Wig, and Silk Dress were the best items you could find for the subquest.
The gateway that Cloud confronts Sephiroth at in 012 is at Mount Gulg, a circular mountain in a field of snowy peaks — it's the Northern Crater! ... Okay, technically Mount Gulg is in the south, but the point is the same.
Sephiroth's "Oblivion" is the attack he begins his Kingdom Hearts II boss battle with. Shadow Flare's original graphics in the Japanese release of the first game also took their appearance from the Kingdom Hearts series, and his "Know your place" victory quote is likewise taken from his Kingdom Hearts II battle.
Hell's Gate is the attack Sephiroth famously used to kill Aerith. This was taken to its logical extreme in 012, where the A.I. is specifically programmed to use Hell's Gate on Aerith when she's called as an Assist to use Holy.
Two cross-company gags: Tifa has an attack called "Falcon Dive" and her Premium Heart gloves have the Kingdom Hearts logo on them.
Tifa begins her EX Burst by landing on the "back wall" and jumping off to kick her opponent, the same move she made when fighting Loz in Advent Children.
Aerith's pose when casting Cure is the same pose as when casting magic in the original game.
His encounter quote to Laguna in 012 ("This guy's like a bad dream") refers to how the Laguna flashbacks were perceived as dreams by the main party.
Ultimecia's quote "Reality is harsh, is it not?" is a reference to her speech at Deling City while possessing Edea. The reference was Lost in Translation, though, since the English speech differed greatly from the Japanese.
Her line when using Hell's Judgement ("Absolute denial! End of existence") is taken from her introduction in the final battle ("Time shall compress. All existence denied").
Ultimecia's Victory Pose and her EX Burst pose are the pose she takes before the final battle.
Laguna's lack of direction refers to the Running Gag in his original game that he could never find his way around.
He warns the Emperor when facing him "Don't fall for your own traps." This is the same warning Laguna gave Kiros and Ward in the Centra Excavation Site ("It'd be idiotic to fall for our own trap").
The name of Laguna's EX Burst (Look, the faeries are here!) references how Laguna and his party fought much more efficiently when Squall's party was helping them fight and thought that they were Faeries empowering them. Additionally, all of Laguna's weapons turn gold, referencing the Aura spell which made party members invulnerable.
All of Zidane's Trance skills from the original game appear as attacks.
His intro to Shantotto is "If I win, you owe me a date", a reference to his bet with Garnet that she owes him a date if he wins the Festival of the Hunt.
When Zidane rescues Squall from Garland and Ultimecia, he says "Do I need a reason to help someone?" This is his signature line from Final Fantasy IX, appearing during one of the opening title cards as well as in-game.
After Kuja kidnaps him, Zidane escapes from Pandaemonium, the same place Garland imprisoned him in.
Kuja's dialogue when someone other than Zidane confronts him in Shade Impulse ("I have nothing left to fear! But I refuse to die alone... You will all join me!") is what he says when defeated as Trance Kuja ("I won't have to be afraid anymore... but I'm not gonna die alone. You're all coming with me!").
Kuja's poem when Zidane confronts him is the same one he recited before attacking Alexandria.
Kuja's pose when using Ultima and ending his EX Burst is the same one he took when he destroyed Terra with Ultima.
Zidane and Kuja both reference their game's version of Garland when facing him. Garland responds in kind.
His entire fighting style, dodging and using a counterattack, is based on the abilities of his Caladbolg, which came with the "Evade and Counter" ability. Note that Tidus equipped the Caladbolg when entering EX Mode.
Tidus's exclusive weapons are Blitzballs that Wakka uses.
Tidus's story is narrated in a How We Got Here manner, the same way most of the original game was told as a flashback from the party at Zanarkand.
At one point, Tidus claims he feels the urge to yell and runs past Firion screaming like a lunatic. He pulls much the same stunt outside Kilika Temple. Without the running, though.
Jecht's Theme Naming with his attacks is the same theme the Final Aeon used for its attacks. Jecht Beam, Triumphant Grasp, and Ultimate Jecht Shot are all attacks the Final Aeon used.
One of his introductory quotes and a battle taunt is to tell his opponent not to cry, a remark he often directed at Tidus.
Yuna's pose when ending her EX Burst is the same pose she takes in a promotional render.
When using the Megaflare HP attack, Yuna spins her staff over her head. This reflects the gold wheel behind a fully summoned Bahamut that would spin to charge up Bahamut's Megaflare in X proper.
Her Mirror Match quote is to ask if the other Yuna is an imposter, referring to when LeBlanc stole her dressphere in Final Fantasy X-2 and disguised herself as Yuna.
The name of her ultimate weapon, Spira's Hope, is something Seymour called her.
When she gets lost without Jecht, Yuna whistles to see if Tidus will come find her, just like he told her to do.
The rivalry of the FFX characters with the Emperor, Yuna in particular, is one giant reference to Seymour.
The Grind Boots system in Dissidia could be a reference to the scene in X when Tidus and the other Guardians grind along cables from the airship to crash Seymour's wedding.
All of Shantotto's HP attacks are "Ancient Magic", a special set of powerful spells that give the target an elemental weakness. The order Shantotto's spells chain — Fire -> Water -> Thunder -> Earth -> Wind -> Ice — is the order you'd cast them in in an ideal scenario, because the next spell in the chain is effective against the last.
The AP needed to master Shantotto's Bravery attacks is in ascending order of the level you'd learn the spells in the original game.
When Shantotto loses, she turns into a doll, referring to an event battle where the player can duel Shantotto, but it turns out to be a doll she brought to life to fight in her place.
In the original Dissidia, when fighting Zidane, Shantotto asks if he is a Mithra due to his catlike appearance.
All of Prishe's attacks are attacks from her original game, and the Skillchains resulting from her Bravery combos are the same Skillchains you'd get in XI from doing a combo with the same attacks.
Prishe's EX Burst refers to the five Mothercrystals, items the player has to collect to defeat Promethia. The shard of crystal she flings to end the EX Burst is the Star of Tavnazia, a magicite crystal she flings at Promethia to destroy it.
Prishe's quotes when using Nullifying Dropkick and EX Revenge are shortened quotes from when she uses Nullifying Dropkick and Auroral Uppercut in the original game — "You can't stop the tide of mortal existence!" to "You can't stop it!" and "Time for a taste of knuckle sandwich a la Prishe!" to "Knuckle sandwich a la Prishe!"
Upon meeting the Warrior of Light, Prishe takes it upon herself to choose a name for him. Prishe often called the Player Character nicknames in XI.
Sentence, Enrage, Lunge, Circle of Judgment, Guilt, and Innocence are all attacks Gabranth uses in his original two battles.
Gabranth's line to Shantotto ("There is no future for the bystander. As there is naught he can defend") is based on what he says to Reddas: "Without power, what future can you claim? What good [is] a kingdom you cannot defend?"
Gabranth's calls of "Your life ends here!" and "By my sword!" are taken from his line when using Innocence ("Your life ends at my blade!").
Gabranth's victory quote "Even a stray has pride" is what he says when he attacks Vayne during the game's final set of boss battles.
Each of Vaan's weapons appears identical to how they looked in the original game — his base weapons are the weakest equipment types of their classes, and his EX Mode weapons are the strongest.
Vaan randomly calls out "I'm Basch!" when using his EX Burst, referring to his infamous scene of running around Bhujerba calling himself Basch.
Vaan asking Ultimecia, Shantotto, and Prishe of their ages in his pre-battle quotes are referencing Fran. Note that all these women are somewhat Younger Than They Look.
Vaan and other characters mention his dream to own an airship and be a Sky Pirate.
One of the Mognet chains of letters in 012 is about a helper girl from a shop who's missing. She got kidnapped by a group of Bangaas mouthing names like "Bal" and "Thier", but was later saved by a sky pirate. This is exactly what happened to Penelo in the original game.
All of Lightning's HP attacks are attacks either she or Odin use when she summons him. The button commands to input attacks in her EX Burst are the same commands used to attack in the original game.
Lightning's HP attacks scatter rose petals when they land. When Odin is summoned or transforms, rose petals are seen scattering as well.
The ability of Lightning's EX Mode to instantly Break opponents low on Bravery is based on the Lionheart/Ultima Weapon's Quick Stagger ability, which staggers opponents once their stagger gauge is 90% full.
Her EX ability to nullify wall rush damage is a reference to the zero gravity device she uses in XIII, a Grav-con Unit, to make long drops without injury.
The visual distortion that appears when using Army of One is the same graphic that Full ATB skills had originally.
Lightning's exclusive weapons reflect the weapon upgrade system of the original game — the Blazefire Saber is traded to buy the Flamberge, which is traded for the Omega Weapon; and the the Axis Blade trades for the Enkindler.
The name of Lightning's Manikin, Fleeting Flash, refers to her explanation of her choice of name: "Lightning. It flashes bright, then fades away."