I couldn't miss the chance to practice my drawing!
Disguises are a key plot element in several Final Fantasy titles. Unlike an alternate outfit, a disguise is not under the player's control. Rather, disguises appear frequently in a given story to convey an element of stealth or surprise.
There are two open instances of disguise. Gutsco the Rogue exposes himself as the dark beast Salamander under the influence of the Fire Crystal. Garuda infiltrates Saronia as the chancellor "Gigameth", corrupting its king and inciting a war. The king, however, breaks free when Prince Alus intervenes. Gigameth almost succeeds in forcing the King of Saronia to murder his own son, but in breaking free, the king resolves to sacrifice himself, believing that Alus is of greater worth.
It is mentioned Edward Chris von Muir "disguised himself as a bard to avoid attention". This would imply he was not a bard to begin with, but it is likely that because Damcyan is a country of bards, he has been educated in the ways of a bard, which would explain his skillset.
At an unknown point in time prior to the opening, Cagnazzo killed the King of Baron and assumed his likeness as a disguise. None suspect anything amiss until years later, when "the king" develops a lust for crystals. It is not known who initially discovers Cagnazzo's deception, only that several people suspect as much. He reveals himself when Cecil returns to Baron Castle as a Paladin.
Cagnazzo takes on a subordinate in Baigan, who also disguises himself as a human. His ruse is debunked by Palom and Porom, who note that his acting is as "subtle as a crutch". It is unknown whether Baigan was human or a monster to begin with.
One may bear witness to a dancer in Fabul who appears to be a woman, but throws off a disguise to reveal that he is a man. Similarly, if Cecil as a Dark Knight visits the inn at Mysidia, a dancer will hypnotize him, then turn him into a pig and run off as an old crone.
The Eblan Four are masters of disguise, and so exemplify the essence of ancient ninja. Each uses the art of disguise to infiltrate his or her assigned mission field. Gekkou masquerades as a monk in Fabul; Zangetsu poses as a dwarf in the underworld; Izayoi becomes a guard trainee in Troia Castle; and Tsukinowa goes undercover as an apprentice mage in Mysidia.
Being a dark warlock born an enchanted tree in the Great Forest of Moore, Exdeath can disguise himself as all manner of wood, once even hiding as a splinter in Krile's hand. When the party visits the Great Sage Ghido, Exdeath separates from Krile to return to his human form and spar with Ghido.
Exdeath's Demons of the Rift also disguise themselves in varied attempts to trap the heroes. Halicarnassus is but an example of this, posing as a damsel-in-distress prior to facing off with the party.
Celes impersonates the opera singer Maria, the object of Setzer's desire, at the emcee's request to prevent abduction of the latter. Though Ultros throws a wrench into the party's plan to save Maria, Setzer still manages to nab Celes in her stead, but Celes turns the tables on him and uses her doppelganger status to enlist his aid. Both Locke amd Setzer marvel at how beautiful she looks.
Edgar changes his appearance and assumes the name Gerad to conceal his identity as king of Figaro to persuade the Crimson Robbers, who were previously detained in the castle's prison, to reveal the secret path to it.
By the time the party reaches the Cargo Ship, each has disguised himself/herself as a Shinra soldier. Even Red XIII joins in, attempting to stand on his hind legs near the crow's nest of the ship. Barret wears a sailor suit, where Cloud might comment that he "looks like a bear wearing a marshmallow". The ladies of the party find this amusing, even suggesting that Barret keep the suit for nightwear.
The inhabitants of present-day Nibelheim are Shinra staff disguised as townspeople.
In Junon after the Meteor is summoned, Cait Sith disguises himself as a reporter in the conference room and incapacitates Scarlet. If Yuffie was obtained she also disguises herself as a news reporter and rejoins with the group.
Jenova would seem the ultimate master of disguise, as it is able to project any being it wishes to.
Princess Garnet wears a White Mage robe to disguise herself while attempting to run away from Alexandria Castle. During the same sequence, Tantalus Theater Troupe members, including Zidane, pose as Knights of Pluto in the attempt to kidnap Garnet, only to have her flip it into the escape plan. Afterward, Garnet pretends to be a regular peasant girl and takes the alias "Dagger" to conceal her true identity. In truth, however, Garnet is a summoner named Sarah from Madain Sari, orphaned while she and her mother were caught in a violent storm, and later adopted by the Alexandrian royal house when the real Garnet passed due to illness.
In the opening event, Leblanc uses the Songstress dressphere to disguise herself as Yuna. Meanwhile, Yuna wears a moogle costume as a disguise during Leblanc's concert in Luca. In Chapter 2, the Gullwings infiltrate Chateau Leblanc disguised in Leblanc Syndicate goon uniforms.
Gabranth (given name Noah fon Ronsenburg) is an identical twin with Basch fon Ronsenburg, and was able to impersonate the latter during negotiations at Nalbina Fortress while Basch and his detachment tried to reach King Raminas to stop them. This sets Gabranth up to frame Basch for Raminas's assassination.
It is unknown how Princess Ashe staged her own death, but she also poses as Dalmascan resistance fighter "Amalia", who joins the party in the Garamsythe Waterway and is captured after the battle with Firemane.
Larsa Ferrinas Solidor opens his role in the story under the name "Lamont", primarily to blend in with the locals as he investigates the activity in Bhujerba's Lhusu Mines. His cover is quickly blown by the party.
A radio onboard the Strahl can record the voice of any who so much as come near the ship, whereupon the speaker can impersonate any captured voice via synthesis.
Barthandelus is fal'Cie who is a a master of illusions. He governs Cocoon under the guise of Galenth Dysley, and once masquerades as Serah Farron when he travels to Oerba to meet with Lightning's party. Lightning and Snow see through his disguise as the "Serah" they meet acts nothing like the Serah they know.
In Yusnaan, Lightning poses as a savior-playing actress during the Song of the Savior stage play to secure a way into Patron's Palace, as the Augur's Quarter where the play takes place has a tall enough statue that can be used as an entry point into the palace.
Yda Hext of Ala Mhigo died in a war before the beginning of the events in Final Fantasy XIV. Her little sister Lyse Hext disguises as Yda and continues fighting to liberate her homeland and working with the Scions of the Seventh Dawn where Yda was a member of.
Although not an actual disguise, Ardyn when confronting several Lucian Royal Guards at the Magitek research facility hallucinated the various members as being Somnus Lucis Caelum. Similarly, while not a true disguise, Bahamut conjured an illusion of Ardyn's long-deceased lover Aera Nox Fleuret to torture him into accepting his destiny of being slain by the chosen king, which Ardyn realized.
Gladiolus briefly disguises himself as a Hunter hired to quell a daemon infestation within the power plant at Lestallum. He anonymously cooperates with Noctis while donning full thermal gear, although Noctis recognizes his voice.
Ardyn Izunia can create illusions and make himself and others appear as someone else. His entire appearance could be seen as a disguise, as black markings at times appear on his face, showing how he is corrupted by the Starscourge, something he conceals unless he deliberately wants to show others his true nature.
The Astral Shiva after being "killed" upon awakening took the form of a human woman named "Gentiana," who acted as the caretaker for Lunafreya Nox Fleuret.
In Final Fantasy XV: Episode Ardyn, Ardyn takes on the appearance of Mars Sapientia, an Insomnian border patrol officer, to sneak into the city undeterred. It is implied that he eliminated the real Mars via his daemonification abilities. Although the disguise is not shown during gameplay, dialogue and certain cutscenes indicate that he maintains the disguise up to and including when he confronts Regis Lucis Caelum at the Citadel.
In Final Fantasy XV: Episode Ignis, Ardyn appears in the guise of Gladiolus Amicitia, but Ravus Nox Fleuret sees through the ruse when "Gladiolus" ignores the wounded Noctis and Ignis, and walks straight up to him instead.
Ardyn switches places with Prompto Argentum on the train through Niflheim. In Chapter 11, Prompto says lines he has never uttered before, and moves slightly differently than before, the way he stands up and his swagger walk being the most noticeable. Similarly, "Ardyn's" statements when Noctis pursues him on the train have him behaving in a way unlike how Ardyn normally acts, such as running away and saying "dude, are you seriously trying to kill me?" When Noctis catches up with the duo atop the train, he finds "Ardyn" holding "Prompto" at gunpoint with Prompto's gun. When he attacks "Ardyn", who falls off the train, it is revealed this person was Prompto. The real Ardyn knocks Noctis out to make his escape after taunting him for having been "in the dark".
In Zegnautus Keep, Ardyn disguised himself as Noctis and approached the wounded Ravus, who was delighted to see "his king" and tried to bequeath the Sword of the Father to him. "Noctis" manifested the Sword of the Father, as Ardyn already had it, and killed Ravus with it.
The Order of the Northern Sky kidnaps Princess Ovelia disguised as knights of the Order of the Southern Sky to frame Druksmald Goltanna. In truth, Dycedarg Beoulve is behind the kidnapping, hiring Delita Heiral to carry it out, though he is unaware Delita is a double-agent for Goltanna.
A Glabados Devout lookalike of Cidolfus Orlandeau dresses as him and is willfully slain by Delita Heiral to fake Orlandeau's death.
Unbeknownst to Sumo, Julius disguises himself as a common Red Mage and gets himself lost in the Cave of Marsh, waiting for an adventurer to help him defeat the Twinhead Hydra at its core. As Sumo next escorts Fuji to meet with Bogard, Julius waits to abduct her knowing full well that she is the key to the power of Mana. Sumo's quest then becomes to rescue Fuji for a large part of the story.