Shapeshifter Default Form

A Shape Shifter (or a Master of Disguise or Master of Illusion) can look like anyone, and sometimes anything. But most such characters will have a regular form that they usually appear in.

This is either because they like that particular appearance, because they need to present themselves in a consistent (or more normal) appearance for the sake of others, or it's simply because that's what they and/or their species normally looks like. It usually depends on how their particular style of Shapeshifting works.

For more practical reasons, this is just easier to draw. Or it's implemented so that a single actor can be cast in the role.

The only time this might be a problem is when a shapeshifter is an assassin or otherwise working in espionage. Their enemies have seen the face of the shapeshifter, yet they remain using that same appearance in everything. This is rarely addressed; it is assumed to be part of the Willing Suspension of Disbelief.

There is also variations regarding the nature of shapeshifting within the fiction itself. There might be mass displacement or other limitations.

Of course, in the real world an individual has many options, either superficial (clothing, cosmetics and jewelry) or intensive (plastic surgery and tattoos), to appear as their "preferred self-image." It certainly isn't unlikely that a shapeshifter would have the same desires.

There are usually two types of Default Forms:

Type A: The default shape is simply the shapeshifter's actual appearance. This is often the case if the character is a member of a shapeshifting species or if the shapeshifting has some limitation, like how long the character can be transformed.

Type B: Their appearance is the form they like best. They may have a natural appearance that is completely alien or too bizarre (or just too expensive) to be practical for human interaction; such shifters often become humanlike in most cases. Oddly, few shapeshifters capable of this option seem to have the energy to go for their most powerful form as their Default.

Some shifters can use a combination of the two. Compare A Form You Are Comfortable With, Sleep Mode Size, Super Mode, Morphic Resonance, and (of course) This Was His True Form. Tends to go hand in hand with Coconut Superpowers.

Anime and Manga

 * Albireo Imma's artifact allows for shapeshifting to a wide variety of people, including Gateau Vanderburg, and Nagi Springfield. But the robed appearance is what he really looks like.
 * Due of Magical Girl Lyrical Nanoha, though as a very effective assassin, the only enemies who've seen her default form don't live long enough to squeal about it..
 * Shippo from Inuyasha is a Type A (He is a fox demon who just transforms via magic) while Naraku is a classic Type B example - Throughout the story, he is mostly seen in the form of a young man with long, curly dark hair which originally belonged to a young nobleman he once killed and impersonated. When the impersonating was done, however, he let a little of his demonic nature bleed through, like his red eyes. Later, after some major power-up, he uses a form with lots of spiky bone armor, tentacles and various misplaced eyes when confronting the heroes or doing other dastardly deeds, but is seen in his former, "normal" humanoid form when recovering or going about his daily life at his hideout. While the heroes have often theorized about what his possible Type A form could be like, it is ultimately revealed that he does not have any true form, or any true body for that matter, with the only thing that is truly his own being his soul, thus explaining why he just won't die no matter what the good guys do with him.
 * Mr 2 Bon Clay from One Piece can only use his most advanced techniques in his default form, because they require perfect knowledge of his body's strengths and limits.
 * Most users of Zoan fruits typically use the human form as their default form... because it is a default form from before they gained their powers, after all. Type A either way. Chopper is the only one pulling off a Type B, using his hybrid form as a default form. He even reverts to it when losing control of his powers for some reason.
 * Chopper's default form is probably his hybrid form now, actually. He is unique in that he was an animal who ate the Human fruit, rather than the other way around, and this was accompanied with an increase in intellect that, say, the members of CP 9 wouldn't have gotten.
 * The Mazoku of Slayers are Type B. That can appear to be anyone or anything they wish to, they just have 'default' human forms so that they can be recognized by people they want to be recognized by.
 * While Oolong and Puar of Dragon Ball can assume any shape they want, their default forms are a short, anthropomorphic pig and a strange creature that looks like a fusion between a cat and a bat respectively.
 * In Fullmetal Alchemist, Envy has both a Type A and Type B form. Its Type B form manifests as an androgynous teenager with hair done in long spikes. The Type A form depends on which continuum you reference.
 * In the manga and second anime.
 * In the first anime

Comic Books

 * Mystique of the X-Men. Interestingly done in X2, where Rebecca Romijn played Mystique in disguise -- sans makeup. From X-Men 3, it seemed like the X2 no-makeup appearance would be her normal human appearance, except with dark hair.
 * In X-Men: First Class, Mystique could almost be considered to be Type A and Type B. Her original form is the blue skin and red hair we all know and love, but she spends most of her time as Jennifer Lawrence, much like Rebecca Romijn sans makeup in X2. The fact that, like Clayface, she has to continually put effort into shifting, coupled with the final abandonment of her "regular human" disguise tips her into Type A by the movie's end.
 * Clayface from Batman. Batman: The Animated Series explained that shapeshifting is a acquired skill, or "muscle tensing," so he can't just constantly be in another form.
 * The Marvel Universe has the Skrull, who often hang around in their normal forms even when there's no real reason to do so.
 * Martian Manhunter from The DCU. The familiar alien "superhero" form in the comics is actually a slightly more human-like version of his true appearance, which is kind of playing with this trope.
 * Courier, a shapeshifter who most often appeared in the pages of Gambit's solo series, is an interesting twist on this. Courier's default form started off as a man, but after being melted (while impersonating a woman) and reconstituted by Mister Sinister, became a woman permanently.
 * When he's not fighting, flying, or impersonating more famous superheroes, Hulkling of the Young Avengers looks like an ordinary sixteen-year-old boy.
 * All the Endless in The Sandman can change their looks at will, but they all have default appearances they stick to when they're among other immortals. Morpheus usually looks tall, thin and pale, with messy dark hair, but he occasionally shows up in other forms appropriate to the person he's talking to -- for instance, when visiting the dream of a cat, he looks like a cat.
 * Or, when seen by the Martian Manhunter in the first volume, as Lord L'zoril, a giant flaming head. Considering that the Martians' weakness was fire, nightmares must have been common.
 * Death's favorite form is that of a perky goth girl. She even appeared (briefly) in this form in a story set in ancient Greece, when her nephew Orpheus visited her in her home (which initially appeared as a slightly cluttered late-20th century apartment). The sight disturbed Orpheus so much that she promptly changed herself and her home into a form he was more comfortable with.

Fan Works

 * In With Strings Attached, George's default form is sort of Type A: his 21-year-old body with any changes he might have made to himself, like a new hairstyle. However, since he has no time limit or stress in other forms, he will cheerfully stay other things as long as he feels like it.

Literature

 * Played against in Larry Niven's What Good is a Glass Dagger?, wherein.
 * In Octavia Butler's Wild Seed, the character Anyanwu takes on different identities when moving from place to place, and is able to change her race, gender, and even her species. In private or with someone who knows her secret, she reverts to the form of a beautiful, petite twenty-year-old African woman. This is the original body she had before her mutant abilities first developed.
 * All users of Andalite morphing technology in Animorphs have a default form which they must revert to if they wish to take on a new animal form. There is also a time limit to how long one can remain morphed; exceeding this time limit results in Shapeshifter Mode Lock that not even reapplication of the morphing tech can fix. Tobias falls victim to this early in the series, becoming trapped as a red-tailed hawk; later in the series he regains his ability to morph thanks to the Ellimist, but now has the hawk as his default form.
 * Given a twist in Tais Teng's SF short story "Gekleed in Twijfelachtig Vlees" ("Dressed in Doubtful Flesh"). Problem solver Percy d'Arezzo (y Mac Shimonoseki) is hired by a shapeshifter who has forgotten his true form. Percy proceeds to take litmus tests for a baffling gallery of shapeshifter species in an attempt to solve the problem by elimination.
 * In The Bartimaeus Trilogy, spirits are described as having both a Type A and a Type B form. All demons have a default form, but they generally do not assume it on the mortal plane because they look slightly repellent (hell, even some spirits prefer not to see each other’s true forms). Instead, most spirits generally refer back to a form most humans are comfortable with, which is usually the form they took when they were first summoned. Which doesn’t mean it can’t still be scary.
 * The Were Hunters in Sherrilyn Kenyon's Dark Hunter series can change into a specific animal.
 * In Robert E. Howard's Kull story "The Shadow Kingdom" the Master of Illusion Snakemen are really reptilian headed men.
 * Boggarts in Harry Potter are rumored to have a true form, except nobody knows what their true form actually looks like; the instant a Boggart is spotted, it immediately transforms itself into something else.
 * The only person who does know, is Alastor "Mad-Eye" Moody, as he was able to see inside a dresser one was hiding in, thanks to his magic eye. Sadly, he doesn't say what it looks like.
 * Tonks, a Metamorphmagus, is also a mild Type A example. It appears that she changes her hair dramatically for day to day wear, but rarely changes the shape of her face or her eyes, which is how Harry consistently identifies her.
 * In Consider Phlebas, Horza, a member of shape-shifting race of alien mercenaries, spies, and assassins averts this trope pretty hard. When he's picked up by a salvage ship after being left adrift in space, he immediately begins modeling his form on the hulking Jerkass captain (he had been in the form of an old man from his last assignment) anticipating the need to kill and replace the man down the line, which would be easier if he already had the body copied and then could just change his face when the time was right.
 * He does revert to a true form, but a disturbing dream sequence earlier in the novel suggests that he might not have even recognized that face in the mirror (he may have been a different member of the same race who lost himself in impersonating Horza for an assignment a long time ago
 * In Mistborn, the true form of the shapeshifting Kandra race is a big blob of tissue that essentially resembles a giant amoeba. They very rarely use this form, however, since in order to take the shape of someone or something a Kandra first has to ingest the one thing they can't turn into- a rigid skeleton. There's some crossover with type b, since although Kandra normally use the bones of whatever individual they're replicating, among themselves they use artificial skeletons called True Bodies that set a preferred shape for that Kandra, and are often fanfically inhuman.

Live-Action TV

 * Supernatural: The Trickster, although he's been shown to be able to assume other forms (Doctor Sexy, the guy he dropped in a wormhole) tends to stick with the one played by Richard Speight Jr. That form actually consisted of the entirety of his first appearance, sans wardrobe changes.
 * Star Trek: The Original Series episode ''Whom Gods Destroy". Lord Garth is a human being who learned the ability to shapechange. His default shape is his original (human) body.
 * The X-Files: the Alien Bounty Hunter first appeared in "Colony" in the form of a Russian pilot played by Brian Thompson. While he could take on any form, he most often seen in the appearance of the pilot. It wasn't until "The Unnatural" that his true form was revealed to be that of a Grey alien and that he was using his current human template as far back as 1947... long before the events of "Colony". It was further revealed that there may have been more than one ABH but that they all had the same 'default' appearance since Mulder saw a number of Greys after being abducted and they all bore the same human form.

Mythology

 * Older Than Feudalism: Most gods of Greek Mythology who can shapeshift (Zeus, I'm looking at you here) have a normal, everyday form. Of course, Zeus had a preferred form and a true form, so he was both A and B. He didn't appear in his true form to mortals, for reasons Semele discovered just before she burnt to death.

Tabletop Games

 * In Exalted, each Lunar has three "default" forms: their original human form, their totem animal, and their Divine Beast Transformation. When their Anima Banner reaches a certain level, they are restricted to these three forms.
 * The vast majority of shapeshifting creatures and classes in Dungeons and Dragons follow this trope, like the Dragons, Doppelgangers and Changeling. In the case of the changelings of Eberron, one of the three philosophy (the Reality Seekers) are based on this. They remain in their natural forms most of the time.
 * Tzeentch's Changeling subverts this hard, as it doesn't even remember what its original form looks like. Tzeentch knows, of course, but he's not telling...

Video Games

 * Druids in Warcraft, although some have been shown to have given in to feral instincts after staying in one form for too long.
 * Fire Emblem Has Manakeetes, who are basically humans with wings. They need special stones to access their dragon forms.
 * And don't forget Chameleon-class characters like Xane, who are true shape-shifters with a Type-A default.
 * In Sonic Heroes, after, he chooses to take on a larger, spikier, eviler-looking form based on his original form. When he's defeated though, he reverts to his very first form.
 * Doopliss in Paper Mario 2 has his default form he reverts to when defeated or not transformed into something else (which looks like a Bedsheet Ghost with party hat), as do possibly the Duplighosts in Paper Mario 1 and Mimi in Super Paper Mario.
 * Touhou 12's Extra boss Nue Houjuu is a Master of Illusion youkai who exploits the fear of her true form. Her true form is better described as a Japanese teenager with messy crow black hair and strange wings.
 * It's debatable whether Alex Mercer of Prototype would be considered a Type A or Type B form of this trope. He does use his appearance before being infected as a default form, however
 * James Heller, however, is a Type A.

Webcomics

 * April Fools' Day from Holiday Wars has a default form where he looks like a scruffy punk from the 80's.
 * Jymre from Hitmen for Destiny usually appears as human, but in his real form he is a weird-looking alien (see here).
 * For El Goonish Shive shapeshifters this seems to be the main way they're shown. The default forms are also said to be most powerful. Raven is shapeshifted most of the time, but returns to his real face when fighting and later uses an illusion for disguise when he expects to need all his power. There may be some debate as to which one is the actual default/normal form for Grace: human/squirrel with Cute Little Fangs is seen more often than the three-tailed spiked squirrel of death mode, as the traits of her strongest parent species are said to be inactive. They also include ability to mix in acquired forms as well, thus after being turned into a half-hedgecat she sometimes adds hedgehog spines to hybrid forms as well.

Western Animation

 * Ben 10. His Phlebotinum only allows him to change form for a set period of time, afterward he changes back into his normal form. In the future of "Ben 10,000," he unlocked the master code removing the timelimit, and he instead chose the really fast XLR 8 as his default form.
 * In Ben 10: Ultimate Alien episode "Ben 10,000 Returns",
 * In The Fairly Odd Parents, nearly all of the magical creatures have Type A Default Shapes.
 * Beast Boy from Teen Titans stays humanlike when not an animal.
 * Madame Rouge's default form can be described as The Baroness and The Vamp (might by a type B- it's never said if it's her true form or merely a preferred one).
 * On the other hand Beast Boy from Young Justice is a type B. He has a (green) human form but usually shape shifts to look like a human-monkey hybrid.
 * Master shapeshifter Amorpho from Danny Phantom is really a faceless ghost in a black trenchcoat/hat.
 * Pain and Panic Hades' minions from Hercules can assume any shape they wish they can also disguise their voices, their default forms are a fat pink demon and a skinny green demon respectively.
 * In Futurama, Alkazar courts Leela and other aliens by shapeshifting to resemble a male of their species. When Fry and Bender blow Alkazar's cover, Leela and his other wives beat him up until he reveals his true form: a 3-foot alien cricket.

Anime and Manga

 * Envy of Fullmetal Alchemist. His/her default form is rather conspicuous looking, with rather feminine attire and unusual hair that resembles the leaves of a palm tree. However he/she chooses to keep this form because he thinks it's cute. This is not his/her real form in either the anime or manga, but what is it incredibly different, as in the anime it's while in the manga it's what could best be called a, though
 * In Inuyasha, when we first hear about Naraku, it's like shapeshifting was going to be a significant part of his arsenal, and it was how he'd gotten the drop on Miroku's grandpa. However, within the series, his mask is always worn until he takes on the form of a certain feudal lord, impersonating him for that two-parter... and from then on, that's the face he always has, whatever he may be doing with the rest of his body. The idea of turning into one of the cast and kindly asking whoever has the jewel shards if he might hold them for a moment never seems to occur to him.
 * Probably because of the five main cast members, at least two could sense that he was a demon and at least one could tell they smelled different.
 * The Tower Guardians from Bizenghast are a combination of both types, since both their animal-like form and their human form are their real forms. They are put in with Type B because they spend the most time in whichever form they like best, with Edaniel liking his animal form and Edrear preferring his human form.
 * Alucard from Hellsing. He states multiple times throughout the series that "My form is of no concern to me", or anything along those lines. Basically, he doesn't care what he looks like, just that he needs an appearance.

Comic Books

 * Xavin, a Skrull in Runaways, was originally sexless, but when (s)he began a lesbian relationship, his/her female human form became the default. Though like all Skrulls, (s)he will revert to skrull form if rendered unconscious.
 * Karolina later determined that Xavin's "true" self was the female body s/he reverted to when they were being romantic, because that was the form Xavin took when s/he temporarily stopped focusing on her physical form while arguing with Karolina.
 * M'gann M'orzz, the DCU's Miss Martian. Her preferred default is the green-skinned redhead usually seen in the comics, with her true form being one of the monstrous White Martians.

Film

 * The Terminator had the lanky Robert Patrick police officer T-1000 or the supermodel Kristina Loken Terminatrix T-X. Their true appearance is a liquid metal blob and an endo-skeletal robot, respectively.
 * Catherine Weaver of The Sarah Connor Chronicles spends most of her time in a form played by Shirley Manson. She's also pretending to actually be the person who's form she's wearing, so she would retain that one.
 * The aliens (the ones in the silver jumpsuits) in Galaxy Quest were actually tentacled beasties, prompting an onlooker to exclaim "Oh, that's just WRONG!!" when one's tentacles become visible as she embraces and smooches a human crewmember. Their default forms were humans, with Vulcan-esque hair styles.
 * Jaclyn from Igor is usually seen in her "Dr. Schadenfreude's Girlfriend" guise, though she changes into other doctors' girlfriends, thanks to a set of shapeshifter pills.
 * In Star Trek VI: The Undiscovered Country, Kirk and McCoy are aided in escaping from a prison asteroid by a chameloid, whose default appearance is that of the lovely Iman. When Kirk questions whether that's her true form, she responds "I thought I would assume a pleasing shape."
 * Loki of the Marvel Cinematic Universe is revealed in Thor to be unknowingly using his illusion powers to create a glamour that hides his true form- a blue-skinned Frost Giant. Since Loki thinks of himself as Asgardian and hates his true species, he keeps the glamour on afterward.

Literature

 * In the Garrett P.I. novels, shapeshifters fall under type B. It's mentioned that one of the unnamed shifters takes on the looks of a soldier he fought with during the war, several decades before the current story and a few months before the entire group of shapeshifters pull a Face Heel Turn.
 * The Valar and Maiar of JRR Tolkien's Silmarillion (in particular Morgoth and Sauron) lose their ability to walk around as "unclothed spirits" if they invest too much energy in a form. In the latter case, they assumed human form, tall dark and terrible and after being wounded or killed off too many times, lost the ability to Shape Shifter into a pleasing appearance.
 * The titular djinni of The Bartimaeus Trilogy is a shapeshifter, but his preferred form is that of his former master, Ptolemy. He takes the form as a way of remembering his old friend, and as a mark of respect. It's also noted that his shapeshifting has a very strong Egyptian bent in general (Ptolemy was Egyptian, just to be clear). For example, if he becomes a cat, its a desert cat. If he needs to be an insect, it's a scarab beetle.
 * Other spirits also have a few regular fallback forms--Faquarl favors the form of a chef, for example.
 * The Gys-Voolbeerah of the Perry Rhodan universe were an interesting case of this due to having actually forgotten the original form of their species. As a result, an individual's 'default' form was generally what they felt comfortable with at the time, often inspired by past impersonations.
 * Sang-drax of the Death Gate Cycle usually appears as either an elf lord (when he wants to be charming) or a giant snake (when he wants to be Nightmare Fuel). Neither is his true form, but the snake is implied to be the closest he can get to it without breaking the brain of whoever he's talking to.
 * The aliens from Roswell High would be this type. Although, they do seem to have an automatic human shape as a kind of default adaptation.
 * The eponymous Eldritch Abomination from the Stephen King novel IT takes many forms within the course of the story (usually the worst fear of the person it's antagonizing at the time), but its favorite form is that of an Evil Clown with balloons called Pennywise.
 * In Paranormalcy, Lend's true form basically a water being, however his default form is a teenage boy, in order for him to go to school like a normal person.

Live-Action TV

 * Odo of Star Trek: Deep Space Nine. Makes sense as he is an authority figure, but on the other hand not skilled at imitating humanoid faces, so he created his own "face" (he based his other features on the appearance of the scientist who first studied him). His true appearance is a jello-like blob.
 * Later, the Changelings are shown to use the same rough imitation of a humanoid face as their Shapeshifter Default Form even though they can mimic humans perfectly when they want to. This is probably because they never really had a solid default form, since their only interactions were with each other and the Vorta, who were genetically engineered to see them as gods no matter what they looked like. When they met Odo, they used this form to make him feel comfortable and eventually adopted it, since it was the only distinctive, recognizable form they had when dealing with the outside world...like, say, fighting a war.
 * Odo is a bit odd in that he can flawlessly impersonate anything else, such as a dog or a bird, but can't get a humanoid face right. He would disagree that he can do animals well, though, in the same way that artificial faces that are too human-like to humans fall into the Uncanny Valley. In one episode they meet up with an Odo who had an additional 200 years of practice and he was far better capable of creating a more realistic face.
 * Q from Star Trek: The Next Generation. He has a default human form with no real reason given, and he experimented with using another form on his second appearance, but he has little reason to change his default human form, as he wants to be recognized. One assumes that the Q don't even have a physical form, the closest we ever see is a diamond flash of light.
 * John de Lancie's Q once recognized another Q (played by Corbin Bernsen) in human form as the particular Q the latter was, and further recognized the Q who took the name "Quinn" on Voyager as who he was. Given the Bernsen Q was recognized when de Lancie's Q was depowered it could be that he was familiar with the standard human form that Q took on.
 * Or maybe the Bernsen Q just tinkered in his brain until he recognized that particular human as a Q. They are (or claim to be) omnipotent, after all...
 * Likewise, the Allasomorphs in Next Generation hung around in humanlike forms while visiting the Enterprise; they are eventually revealed to be Energy Beings in their true forms.
 * In Heroes, Master of Illusion Candace is Type B when she's knocked out, and Type A when she's killed. Even though in the latter, another illusion that she'd cast disappeared. Good job, Internal Consistency guys.
 * Another character was capable of imitating other peoples' appearance; possibly that of anyone he came in contact with. We never got to learn how his ability worked or what he actually looked like before
 * Frobisher in the Doctor Who Expanded Universe. He's a shapeshifter, but is usually in the form of a large talking penguin simply because he likes it.
 * In the original V miniseries, the alien invaders took on human form to disguise their true reptilian nature (as well as their intentions to cannibalize the human race). Oddly, the aliens continued to maintain their human appearance long after the jig was up. (It's possible the human suits had some sort of protective factor against the environment, but it also conveniently kept half the cast from having to don expensive alien makeup before shooting.)

Tabletop RP Gs

 * In Eberron, the changeling philosophy of The Passer is based on this part of the trope: pick an identity from a common race and stick to it, never letting anyone find out your true race, and essentially turning your back on your kind to become a member of your new race.
 * Changelings in Rifts have a Type A default form, but since they are usually so hated they never use it when they can help it. Every Changeling NPC described in a Sourcebook has a "Favorite" form they use for an unofficial default when around friends.

Toys

 * Bionicle: Krahka. Her toy is actually a combination of all six Toa Metru toys, and is the final form she took in The Darkness Below. She has no known real form.
 * The Makuta, mainly because their real form is Pure Energy contained in armor.

Video Games

 * Decoy Octopus averts this slightly in Metal Gear Solid - and much more thoroughly in The Last Days of Foxhound. In MGS, he's only ever seen 'in disguise', and the only way you know what he 'actually' looks like, is from an old photo from his personal file. In TLDOF, he's also almost always in disguise - usually as one of the other characters - and when he's transferred to the spiritual realm, he shows up as an invisible man in a trench coat, remarking that he doesn't actually think of himself as looking like anything.
 * Or was he never there to begin with?.
 * Many dragons in Warcraft use a humanoid form (usually high elves) while interacting with mortal races. In World of Warcraft, players may meet a Bronze Dragon known as Chromie in her Gnome form in several locations, and it is not until the end of a high-level instance that she actually appears in dragon form, and even then only briefly. Krasus in the novel is a similar case, though he prefers his original form. Finally, the raid boss Nefarian is encountered several times in human form. In the real fight, he remains in his human form while setting a horde of dragonkin upon the raid before finally transforming into his real form.
 * Subverted with a minor character in City of Heroes, a shapeshifter working for the Malta group who is theorized to have forgotten what he originally looked like. (Of course, this was mostly so the developers could just use existing models to represent him.)
 * Mimi from Super Paper Mario has the default form of a green, blocky little girl. This is not her true form, which is some sort of horrible spider-monster-thing.
 * The protagonists of Mega Man ZX Advent are both Type A and a variant of Type B; their shapeshifting is linked to a Transformation Trinket, so their Type A form is what they are when they're not using it. The game itself, however, enforces the use of a specific powered form when entering cutscenes or speaking to NPCs.

Webcomics

 * Cassiel from Misfile usually uses her school-girl form on earth, even when it would make more sense to take a different form to avoid detection. The implication is that she is just too lazy or too unimaginative to come up with another one.

Western Animation

 * Nergal Junior from Billy & Mandy usually takes the shape of a short boy with a washed-out complexion and black hair; the form of the first kid he approached and asked for friendship, but rejected him, causing him to attack in rage. His true form, which is never shown onscreen, is apparently unimaginably horrifying, so much so that he is extremely sensitive and self-conscious about it.
 * However, in a later episode, he takes on a grotesque, monstrous form several times to scare people. With its bumpy black skin, tentacles and other features which were shown in partial shots of his true form, this is arguably the first appearance of his actual form onscreen.
 * The Zeta Project (A robot built for infiltration could don virtually any holographic disguise, but always went for a dark haired man in a purple trench coat.)
 * This is actually explored in the first episode; Ro takes him to a fitting room and helps Zeta create a 'default' appearance designed to minimize suspicion. Before that, his default form was a middle-aged man wearing grey, or as Ro put it "Joe Robot".
 * In Gargoyles, all members of The Fair Folk are shapeshifters, but each has one form they prefer. Their true forms, however, are so obscure that Word of God is even they don't know the true form of their species.
 * Bertrand from Danny Phantom is really a green blobby ghost, but he frequents in his human form the most.
 * Inque from Batman Beyond had a slightly human-like "combat form" that had a white blot on a featureless face and her hands were barbed whips or some other weapon. When in a peaceful mood she would take on human features, which is assumed to be an approximation of her human appearance before the mutation serum was used on her, as she still has an oily look. Otherwise she looked just like a blob of ink.
 * Beast Boy from Teen Titans spends most of his time in the form of a green teenage boy, unless he has some reason to be otherwise.
 * In the South Park episode "Cancelled", an alien greets the boys in the form of Stan's father. He explains that this is A Form You Are Comfortable With but they think that's stupid because its reminiscent of Contact. When Najix takes its true form, they scream and quickly ask it to go change into something else. They then spend a few moments going through possible forms (including Santa Claus, Saddam Hussein, Don King, and Frank Sinatra) until they decide on a taco that craps ice cream.