Not a Mask

Camilla: You, sir, should unmask.
Stranger: Indeed?
Cassilda: Indeed, it's time. We have all laid aside disguise but you.
Stranger: I wear no mask.

—The King in Yellow.

A horror trope which has become something of a Dead Horse Trope, as it's now almost always played for comedy. It involves a character seeing an ugly face and begin pulling at it, on the assumption that it's a mask. Of course, it's actually someone's face and the puller will typically be Horror Struck. Sometimes a purely comedic variation will occur with wigs if the joke is that a woman looks like a man. Also closely related to "I'm not pregnant, I'm just obese" jokes. Compare with Your Costume Needs Work and For Halloween I Am Going as Myself. Can be a result of the monster being Mistaken for An Imposter.

Examples of Not a Mask include:

Anime and Manga

Happens to the main character of Angel Densetsu where a new guidance conselor first scolds him for wearing a frightening mask and begins pulling on his face, and then accuses him of mutilating himself to scare people.
In Fullmetal Alchemist, most people assume that Alphonse Elric just really likes wearing armor, since he never even takes his helmet off. In fact, after Al lost his flesh-and-blood body, in order to keep him from dying completely, his soul was bound to the closest substitute in the immediate vicinity, meaning that empty suit of armor is his body.
- In the 2003 anime, there's an omake episode that has the premise that the characters are actually actors. One of the jokes involves the reveal that the freakish looking Gluttony is not an actor.
During the Water 7 arc in One Piece, a ban on masks is put into effect (since there was a carneval going on in a nearby town) after a failed assassination attempt on the mayor. An ugly looking woman out to board the sea train can be seen desperately tugging at her face in order to prove that it isn't a mask.

Comic Books

A very creepy example turns up in an EC story: For years, maybe two, maybe three, this dude has seen this gal with a fabulous figure and a wonderful personality at a Halloween party (and only at that party). Only thing is, she's always wearing this horrible wrinkly witch mask. Finally, he proposes to her, they go get married right after the party- still in their costumes. They consummate their marriage in a hotel, but the kicker is, she turned out the light before they undressed. He dreams that she's still wearing the mask; pulling it off, she wears the same mask underneath. He wakes up, turns on the light, and yep, there she is, wearing the mask. So he pulls it off and... off comes her skin. It was her real face.
The Joker sometimes likes to pretend he's wearing makeup, but that ain't makeup. Well, except...

Fan Works

Inverted in this Doctor Who Fan Fic, as the non-mask-wearing character in question is an attractive Human Alien.

Film

Quasimodo in Disney's adaptation of The Hunchback of Notre Dame. His deformed face is mistaken for a mask, as he is at the Festival of Fools, where everyone is wearing an ugly mask. When he wins, they try to pull off his "mask" , but recoil when they realize he really looks like that. He then has to run away while they throw vegetables at him.
- Actually, they're kind of accepting at first, with some persuasion from the guy running the festival. It's only after the soldiers throw vegetables at Quasi that everyone turns on him.
Used in the first Austin Powers movie, although it was perhaps more a case of Not a Wig.

"I'm sorry, Basil. I thought your mother was a man."

The Archbishop of Canterbury in Johnny English.

Literature

Played straight in Robert W. Chambers's The King in Yellow, a short story collection that inspired H.P. Lovecraft and was a precursor of the Cosmic Horror Story. The quote used at the top apparently comes from the titular play, of which we never get more than a few small excerpts, as it drives its readers insane (no actual performances are ever suggested). The King in Yellow character is implied to be some sort of Humanoid Abomination.
In Beastly Kyle goes to a Halloween party where he startes talking to a girl who asks to see him again but to do so she needs to know what he looks like and you know the rest.
Played straight in The Masque of the Red Death
- Parodied by Death in the Discworld novel The Light Fantastic, explaining why he appeared at a summoning ritual with a cocktail and a sausage-on-a-stick. "The party's nice, but I expect it'll all go downhill after midnight. It's when they think I'll be taking my mask off."
- Terry Pratchett played a similar situation (almost) straight in his short story Turntables of the Night, with the catch that it's from the perspective of a guest at the party (who may or may not be drunk.)
- Maskerade features Death appearing to a man while dressed in a bright red suit and an extremely cheap skull mask. The man demands that Death removes his mask, to which he complies. The man then asks him to remove his other mask...
- In I Shall Wear Midnight, Mrs. Proust sells stereotypically warty and hideous witch masks and gloves, and appears to be wearing a full set. Then Tiffany realizes that the masks she sells are copies of her own face.
The King in Yellow (see above) is also a straight example, from back before it was such a Dead Horse Trope.
Shel Silverstein's poem "Best Mask?"

They just had a contest for scariest mask,
And I was the wild and daring one
Who won the contest for scariest mask--
And (sob) I'm not even wearing one.

In Quozl, the Petting Zoo People aliens are wandering around Disneyland pretending to be people in suits. (The protagonist's sister had written them into her kids' TV show) Hilarity Ensues when the security guards confront them for being dressed up like characters from a rival company.

Live-Action TV

Used in the first episode of Torchwood. The fact that the guy looks like an alien wearing a normal janitor's jumpsuit plays with you.
The League of Gentlemen's Papa Lazarou is not normally wearing makeup.
In the Tales from the Crypt episode "Only Skin Deep", the guy finds out the woman a deranged Serial Killer who murders men and cuts off their faces for her "art" he hooked up with during a Halloween party isn't wearing a mask when he scratches her and draws blood.

Theatre

Cyrano De Bergerac: In Act I Scene I, Cyrano is described by one of his friends, Raguenau (making this Older Than Radio):

Above his Toby ruff
he carries a nose!—ah, good my lords, what a nose is his! When one sees it
one is fain to cry aloud, 'Nay! 'tis too much! He plays a joke on us!' Then
one laughs, says He will anon take it off. But no!—Monsieur de Bergerac
always keeps it on.

Video Games

This happens in Persona 4 in the first meeting with Teddie. While Teddie's head isn't a mask at first, it is detachable, to Yosuke's shock when Teddie takes it off to reveal his hollow body.
Fain of Lusternia. He used to be a handsome leader amongst the Elder Gods, but he partook of too much of the Soulless elixir and his trademark mask became fused to his face. His full title, incidentally, is "Fain of the Red Masque".
- Rendered even creepier by the fact he can still make expressions with it, the metal of the mask violently contorting to reflect his wrath.
Played for laughs in the second Professor Layton game. When the professor and Luke first run into Inspector Chelmey, who Don Paolo had impersonated in the previous game, Luke immediately assumes it's him again. He has to be pried off the victim, who has no idea why Luke is trying to pull his face off.

Web Animation

Strong Bad's mask is his face in Homestar Runner.
- This didn't stop him from trying to take it off once, safely concealed behind his enormous executive chair. (Which then tried to smother him in sweatpants. Long Story.)
In one video by College Humor, which is a parody of Scooby-Doo, Shaggy immediately suspects that a security guard is the culprit. He grabs for the guard's face and pulls it off, revealing...the inside of the guard's face.

Web Comics

Not a horror example, but in Fur Will Fly, when Brad first arrives in the Mirror Universe, he tries taking off Stewart's and Natalie's animal masks. Needless to say, it doesn't work.

Web Original

In the story "Tall Tales" in the Paradise setting, characters who began to see through the Weirdness Censor assume that the Funny Animals they see are humans wearing costumes. Of course, they are all attending a Furry Fandom convention at the time.
In this creepypasta for The Fear Mythos, this trope is applied to the Plague Doctor:

"He had a funny beak face," the child said. "I asked him. I asked him why he was wearing such a funny mask. He told me that he wasn't wearing no mask."

Western Animation

SpongeBob SquarePants once pulled Squidward's face off, thinking it to be a disguise. (Hint: It wasn't.)
- Same thing happened with Mrs. Puffs and the prison guards after SpongeBob and Patrick tried to sneak into prison disguised as guards.
Used at least twice in Scooby Doo, in Scooby Doo and the Cyber Chase and Scooby Doo on Zombie Island, the former with some enemies that originally were fake monsters, and the latter with one of the zombies.
- Another Scooby-Doo example is the Halloween 1976 episode, where Shaggy falsely thought Elwood Crane was wearing a mask.
Hanna-Barbera also did it with Loopy de Loop and Magilla Gorilla.
Used on The Simpsons at the end of "Who Shot Mr. Burns? Part 1":

Chief Wiggum: This isn't Mr. Burns' face at all! It's a mask! (pulls on his face) Oh wait, it is Burns. Heh -- his wrinkly skin lo -- looked like a mask.

- Also, Krusty to Homer in "Homer's Triple Bypass", pointing at his own face: "I got news for ya. This ain't makeup."
- Also inverted by Krusty. In "Bart the Fink", for a while Krusty went under the alias "Rory B. Bellows". The Rory persona looked like a "normal" Simpsons character, that is, with yellow skin, short brown hair and a normal nose. It turns out that it wasn't Krusty without his clown makeup, but Krusty with a disguise that covered his usual clown face... even his red nose was hidden under a fake yellow one!