The Goddess Media from American Gods by Neil Gaiman was like this in her true form. As the humanoid manifestation of The Media, when she wasn't possessing characters on television, she was described as looking like the sickeningly sweet hostess in one of those morning shows filmed in a fake living room.
Kiina in the Novelization of BIONICLE: The Legend Reborn. In the animated movie, she's a Genki Girl, even though the prequel book depicted her as a mean and argumentative person who got into bar brawls, barely had any friends, and would have loved nothing more than to leave the planet. In TLR, when the appearance of Mata Nui presents an opportunity to do so, she adopts a friendly and cheerful persona to get close to him, fearing that if Mata Nui knew what life on her planet was like, he'd give up all hope and never try to help them.
Erzebet Bizecka of Alisa Libby's Blood Confession is Unstable. She's a charming and beautiful young lady who's doing an excellent job at leading her country out of difficult times. Not to mention how kind she is to her servants. Of course, that's just a plot to get them into her dungeon where she kills them and bathes in their blood to preserve her youth and beauty.
The Other Mother from Coraline at first appears to be a very sweet, friendly counterpart to Coraline's real mother. As it turns out she is the Big Bad and it was all a facade to get Coraline to stay with her.
Kaitlyn Werhner from the short story "Dark Red Mind". If you were to see her smile at you with those piercing blue eyes, run. Not that it would help you any.
It's possible to read Agnes Wickfield in David Copperfield as this, considering her life with an increasingly alcoholic, depressed father and an increasingly lecherous Uriah Heep, yet she never loses her smiling willingness to help others. As well, Miss Mowcher is classically Depressed (though she was originally written as The Grotesque, Dickens switched gears and made her a tragic figure who shields herself behind laughs, even at her own expense.)
Lilith de Tempscire from Discworld is a Transferred Stepford Smiler. In Lilith's mind, life should be just like a storybook. As the witch in charge, politically, in the city of Genua, she likes things to be the way people expect them to be—i.e., cooks should be fat and jolly and bustle a great deal, innkeepers should have big red faces, toymakers should whistle and sing the whole day long and tell amusing stories to children, etc. And woe betide anyone who doesn't live up to Lilith's expectations; she makes certain that they suffer for it. To quote the book Witches Abroad, "Lilith held up a mirror to Life, and chopped off the bits of Life that didn't fit."
The first appearance of Ysabell, in The Light Fantastic, is when with a fixed manic smile on her face, she explains what it is to be Death's adopted daughter — stuck, never dying, in the house of Death forever, having been fifteen for nearly fifty years in a place where Time does not apply, with no mortal human beings to talk to — well, not for very long, anyway — and (with a long sharp blade in her hands) explaining how nice it would be if Rincewind stayed for a little while longer...note It is possible that this is another underlying reason why Death chooses to take Mort as an apprentice in a later novel — to restore Ysabell to the world in a halfway sane state.
Joplaya in Earth's Children appears to be cheerful and carefree much of the time, but has a more melancholy side she keeps hidden. Her flirting with Jondalar is often laughed off as jokes with no deeper meaning and she goes along with this, but the narrative makes it clear that she's actually serious and feels despondent that Jondalar has never picked up on this. This worsens after Jondalar returns to his homeland with his fiancee Ayla; although Joplaya puts on a brave face in public and sincerely insists she's happy for Jondalar, she's secretly crushed (Ayla - who is skilled at reading body language - picks up on this and feels sorry for Joplaya).
Fellow Man by Norwegian author Olav Duun has Tale, the wife of sociopathic and Manipulative Bastard Didrik. She copes with her nasty husband and keeps appearances up by smiling. She borders on Stepford Snarker as well. She lampshades it early on:
I am glad I have my grin. In this house, you either grin, or weep.
Carrie, a classic case of Depressed, is actually a deconstruction in Finding Snowflakes as she smiles more to hide the pain from herself than others.
The narrator of the German novel "Für jede Lösung ein Problem" (eng. "A problem for every solution")suffers from clinical depression and plans to kill herself. Despite that, she happily attends family parties and meets her friends as if nothing was wrong, she even confirms her attendance at events set after her suicide. Everyone is noticeably shocked when they read her farewell letters as they didn't see it coming at all.
Mrs. Coulter in The Golden Compass. She puts on a friendly, trustworthy front when in reality she's one of the leaders of an organization that kidnaps young children and surgically removes their souls.
Amy Elliot-Dunne in Gone Girl; she projects a shiny-happy picture of domestic bliss and wifely perfection, but she's secretly The Sociopath who's spent her life putting on false faces and personas in order to both get her way and interact easier with others, notably men who had an obvious "type" in women. This stems from an emotionally neglectful childhood in which her parents compared her both to the numerous miscarried fetuses who came before her and the flawless version of her they created for their best-selling children's book series; this led her to develop antisocial personality disorder along with a deep-seated desire to be loved for the person she truly is (which is, among other things, petty, manipulative, vindictive, and ruthless.) She thought she had found this love in her husband Nick Dunne until she realized that he had been putting up just as much of a front as her. He pretended to be a charming, lovable, "salt of the earth" version of himself while she pretended to be what she calls "Cool Girl" — a woman who conforms to her man's personality and tastes so he'll think she's perfect and non-threatening. Her resentment of Nick's true personality, along with his adultery and forcing her to move to the Midwest, is what drives her to kick off the novel.
Petunia Dursley is a fine example of the sort who initially seems to be her mask. Deathly Hallows suggests that her mask developed as the means to deal with her jealousy over her younger, "perfect" sister Lily getting magic and not herself.
Dolores Umbridge. Part of the reason this character is so effective is that she wraps her sadism and violence in an unnerving Stepford mask straight from her introduction in Order of the Phoenix.
Luna Lovegood is Depressed played straight. She's an Iron Woobie who is bullied viciously for her eccentric personality, and she didn't have any friends until she was a teenager. But despite this pain, she is still happy and cheerful...on the outside. She drops hints occasionally, in a purposefully serene, conversational manner, and this makes the other characters feel uncomfortable. There's a good glimpse of what's going on behind the scenes in the 7th book when Harry discovers a mural that she painted in her room, depicting all her friends, Harry included.
Ryoko Asakura from Haruhi Suzumiya is the Unstable type. Being the most popular girl in her class due to her beauty and kindness, she keeps a cute, caring and friendly appearance, even when she is about to stab you with a combat knife, or when dying. Since she is an Artificial Human, unable to empathize with humans, it is very likely that it is just a fixed masquerade.
Miss America in Haunted (2005) constantly behaves as though she is on camera, working so hard to maintain her flawless facade that naturally her breaking point is just as epic as those of the others.
Part of the reason Will Navidson moved his family into the titular house in House of Leaves was to get closer to his family, including his Stepford Smiler wife, Karen Green.
Akeno Himejima of High School D×D is rarely seen not smiling or giggling, most of the time maintaining a cheerful and flirtatious disposition. However, she probably has the worst Dark and Troubled Past among the members of Rias' Peerage (which is saying a lot) due to losing her mother and blaming her father for not protecting her, and Issei is pretty shocked when she breaks down crying as she tells him of it.
The Hunger Games: Katniss eventually realizes that Effie Trinket's shallowness is a defense mechanism which is her way of coping with her role in the Games.
Felicity in The Idea Of Perfection by Kate Grenville is obsessed with appearance, to the point of avoiding frowning or smiling out of fear of developing wrinkles. More-or-less Empty, since there's nothing of substance underneath her immaculately groomed and beautiful appearance, and contrasting brilliantly with the much more flawed, but likable protagonists, who, along with the flaws, also have goals, interests, and drives, and who actually get things done in the end.
In Death: Allika Straffo from Innocent In Death is either Depressed or Unstable. That's because she knows her daughter Rayleen Straffo killed her baby brother Trevor. She tries to act like everything's fine and okay because she's afraid of Rayleen and what she might do.
Annie Wilkes in Stephen King's Misery. She is a cunning, brutal, and dangerously disturbed woman who hides her psychosis behind a cheery facade and kind smile, making her Unstable.
According to Catarina, Mary has two types of smiles. First is the genuine, affectionate smile reserved almost solely for Catarina herself. Second, there is the "social" smile that she uses as a mask. At one point, Catarina notices the change but does not put two-and-two together that it's because Mary noticed that Geordo was up to something with Catarina.
Mary, who had been smiling at me just a second ago, now suddenly had the smile she usually reserved for social affairs on her face.
In the original Fortune Lover scenario, Keith's womanizing tendencies belie a lonely heart, broken by years of verbal and/or physical abuse from his half-siblings, and then Catarina. Of course, in the work's timeline, Catarina has a major change in personality and makes everyone's lives better.
Elin from Of Fear and Faith is a genuinely happy person for the most part, but she hides severe and traumatizing personal scars behind her cheerful smile and refuses to show anyone else that she's in pain.
William Sleator's Others See Us has Annelise, who is well loved by everyone, including her cousin Jared, until he gains telepathy and realizes she's a Stepford Smiler of the worst sort. At one point he visits her mental landscape, it's an infinite sun-parched desert with her face as the huge sun, and the only other feature is a gigantic mirror, reflecting her face.
The original Pollyanna is Depressed. She maintains her sunny disposition in front of people but she is sad about losing her father and breaks down when she becomes crippled. She gets better though.
Early on in Redeeming Love, Angel acts like her cushy life as the city’s highest-end prostitute is all she could ever want, flippantly laughing off the hero’s suggestions that she might want to escape it—when in fact she has no control over her own life, is deeply lonely, and loathes every minute of her work. As the novel progresses and she is taken out of her “comfort zone", it becomes obvious that she’s really a deeply bitter and cynical Broken Bird.
On the heroic side, Leitha from David Eddings' The Redemption of Althalus. She pretends to be cheerful and witty, but is secretly neurotic, insecure, and self-hating.
E. T. A. Hoffmann's Olimpia from The Sandman (1816) is very much a literary ancestress. Nathanael becomes besotted with her because she has a more "positive" attitude than his fiancee Clara, e. g. to his efforts at poetry. She is an automaton, constructed to be pleasant and thus unable to talk back or criticize.
In The Secrets of Drearcliff Grange School, "Perky" Palgraive smiles all the time, no matter what the provocation (and several of the prefects consider it a challenge to wipe the smile off her face). This is because she's a Meat Puppet for a Puppeteer Parasite that hasn't entirely got the hang of fine motor control or the nicer points of human interaction.
Kira in The Ship Who Killed swings between wildly enthusiastic displays of happiness and explosive rage, covering her profound grief at her husband's death and her own Death Seeker tendencies.
Young Tia puts on the face of a Cheerful Child when around other people. Before she was paralyzed she worried that otherwise either her parents would withhold time with her as punishment or the Department of Child Disservices would take her away and make her go to school and interact with other children. Afterwards, she just didn't want them to worry. As a brainship, she's professional but a bit more willing to share how she really feels.
Especially in The Ship Errant, Carialle insists that she's cured of her old trauma and downplays her anxiety and panic attacks to present herself as cheerful and enthusiastic about the mission.
C. S. Lewis' short story "The Shoddy Lands" (PDF link here) also has its protagonist experience a telepathic vision of a Stepford Smiler's mental landscape. Or... well, it's a misogynistic idea of what CS Lewis imagines a woman's mind is like, very dull and materialistic and unappealing to him, with a vague dread to it, that has the protagonist despising her as shallow.
The over-enthusiasticprincess Amelia from Slayers, if one looks deeper, is Depressed; as a daughter of a prestigious and powerful royal family, she is subjected to horrific violence and carnage as her family battles over the line of succession to the throne. Her Missing Mom was murdered, in-series she sees one of her uncles and her cousin get killed attempting a coup, her sister has long since run away, and her father (the current heir apparent) is a go-to target for assassins. It's summed up well enough in the Light Novel she's introduced in:
"But you know," [Amelia] added, still sporting that strange smile, "I really don't like that you can't trust people in your own family around here." It could've been my (Lina's) imagination, but just then I sensed a great sadness in Amelia behind that bubbly facade. There was definitely more to that girl than met the eye.
So, I Can't Play H!: Initially, it seems Ilia has it all: she's a popular teen idol and a babe, who doubles as a spokesperson for the Merlot Life Insurance company. That is, until Ilia's manager reveals that people used to make fun of her, because Ilia's semi-flat-chested. Plus, her lisp and her natural accent slurred her speech so badly, hardly anyone could understand her. It's left her with an extremely poor self-image. So as long as the spell holds, Ilia brims with confidence, but if it anyone sees, or hears, what she's really like, she runs away in tears.
The titular character of Stargirl, of all people has a tendency to become depressed when she's sad. She is normally an upbeat Blithe Spirit.
Stoner's wife, Edith, in "Stoner" by John Williams, goes through a phase of embodying this trope perfectly.
The Storm (Arav Dagli): Throughout the years she's been married to him, the wife puts on a facade of happiness and lies to herself that she's content with her distant husband. As a result, her smile feels fake; she plasters it on herself every morning and never finds it to look quite right.
Shallan Davar of The Stormlight Archive is revealed in Words of Radiance as a combination of Depressed and Unstable. Due to her Dark and Troubled Past, she must use Lightweaving to repress her true feelings in order to function. Arguably a Deconstruction, as Shallan's feigned chirpiness is not portrayed entirely as a bad thing; in one defining moment, Kaladin is humbled and awed by the fact that even though she has been through as much crap as he has, she can still bring herself to smile instead of becoming a Perpetual Frowner like him.
Yoko Nakajima, the main character of The Twelve Kingdoms, starts out the series as a junior version of this in regards to her home and social life; she reveals later the fear that there was truly nothing inside.
Jennifer North in Valley of the Dolls tends to be this. Harry Bellamy says of her "That smile is glued on." She's unfailingly warm and friendly to everyone and sincerely cares about others' problems while hiding a life full of shame, lies, bitter disappointments, and, finally, breast cancer. Most of the truth is not revealed until long after her suicide.
Countess Rostov from War and Peace is very much like this except when she's talking with her daughters. Pierre Bezukhov's wife Helene would be a subversion in that she goes from having no role in society except being beautiful (and smiling a lot) to one of the eminent hostesses on the Moscow and St. Petersburg scene after getting married.
Angela Wexler has given up her dreams and ambitions to fulfill her social-climbing mother's wishes, making her Depressed with a bit of Unstability, as she vents her frustration by setting bombs, including one aimed at herself.
Flora Baumbach is purely Depressed who smiles constantly to hide the pain from her husband leaving her and her daughter dying.
Glinda from Wicked is essentially this. As such a high and mighty political figure she must keep a happy facade. Made even worse when her best friend, who happens to be the person she loves, is killed. She must act as if she hates her and tell pitiful lies about her. It's debatable if the musical or book version has it worse.
The Irish short story "An Beann Og" (The Young Woman) follows a mother of two who politely smiles at anyone she sees and greets them kindly. She seems perfectly happy as she gets herself tidied up for her husband coming home for dinner but the last line of the story says she feels a small tremble of despair at the thought of her husband.
Male Examples
Todd Bowden from Stephen King's "Apt Pupil" maintains the image of a cheery all-American golden boy even while he's blackmailing the neighborhood Nazi-in-hiding into telling gruesome concentration camp stories. It's all downhill from there.
The Belgariad/The Malloreon: Silk, AKA Prince Kheldar, is asked why he's always laughing at life. His answer: "I've taken a good, long look at the world, and I concluded that if I didn't laugh, I'd probably have to cry."
Telemachon from Black Legion is mostly the Depressed kind. To the outsiders, including emotion-reading Khayon, he's your typical Emperor's Child — indulgent, full of contempt, and with no standards. Inside, however, he's Desperately Looking for a Purpose in Life and has a soul of a poet. When Abaddon proposes him to join the Legion, he promptly jumps ship.
In the Darkest Powers novel The Summoning has Simon Bae, who for his introduction in the first book seems like a totally normal, cheerful kid who just so happens to be locked up with his older brother in a group home for mentally unstable kids. No matter how gloomy and angry his brother Derek is, Simon always remains upbeat and positive, until Derek snaps at him for doing nothing to help find their missing father. This is the first thing that breaks Simon’s happy mask, and he admits that having to pretend to be content all the time when he really wants nothing more than to run away and find his dad is killing him inside.
And again in The Reckoning, when he takes Chloe on a date, only to discover that his suspicions about her actually having feelings for Derek and not for him are true. He admits to having ignored it so he could just keep trying, but upon finding it out for real, his smile once again breaks and he actually leaves Chloe behind in the forest to go be alone for a while.
Could Derek count as well? He wasn’t exactly smiling, per se, but it’s implied that he tried to hide his own feelings about Simon and Chloe’s going on a date and act like nothing was wrong...
Discworld serial killer Carcer is deceptively cheerful and innocent-looking, with his smile putting people off guard...until they look in his eyes and see the monster behind the mask. But of course then you've taken your eyes off his hands, and at least one of them is holding a knife by now. He's the kind of guy who would murder a man for a loaf of bread and then stand over the corpse saying 'Who, me, guvnor?' and almost convincing you.
Durarara!!: Kida is not naturally that cheerful; it's a front he puts up for Mikado's sake.
In Endo and Kobayashi Live! The Latest on Tsundere Villainess Lieselotte, Lieselotte noticed this of her fiance Crown Prince Siegwald before she entered the academy. Not that Siegwald has any mental issues, but his station demands it.
In contrast to his grinning mouth, Siegwald’s eyes had an unreadable blankness to them. They conveyed neither good nor bad. Who could say how much emotion he’d suppressed to achieve such tranquility? When Lieselotte had first asked herself this, she’d wept.
Guy Montag from Fahrenheit 451 has a forced smile gripping his face at all times, even when he goes to sleep. It takes him some time to realize that his "happiness" is not real and actually masks deep unhappiness.
Bryce from Flipped comes off as Empty to Juli's family, but is really Depressed and hides how repressed he is exceedingly well.
David Foster Wallace's short story "Girl with Curious Hair" is narrated by a mixture of Empty and Unstable. One of the narrator's "punkrocker friends" tries to emotionally engage with him while high on acid and is deeply disturbed upon realizing that there is nothing behind the mask.
Skylar St. Clair of Gives Light is Depressed. He has plenty to angst over (a dead mother, vocal cords that don't work, a father who seems to have walked out on him, a social worker who might take him from the only family he's got left, and his sexuality), but never dwells on it for long. Though he would have you think he's The Pollyanna, it becomes increasingly obvious that he's faking it.
Xenophilius Lovegood tries to conceal Depression in Harry Potter and the Deathly Hallows when Harry, Ron, and Hermione come to his house. He pretends that everything is well and good and that Luna herself is only out getting ingredients for soup when he's actually been afraid because the Death Eaters have Luna and have threatened to kill her unless he captures Harry Potter for them, which is just the thing he's attempting to do.
Albus Dumbledore, best shown in Harry Potter and the Philosopher's Stone when he lies about seeing himself holding a pair of socks in the Mirror of Erised (an artifact which reveals a person's deepest desire).
Itsuki Koizumi from Haruhi Suzumiyaalways keeps a constant smile and a cheerful attitude. Granted, he's still mostly sane and calm, but his Stepfordness always creeps Kyon out to no end. But when his smile disappears... you better start fearing the worst! He actually expresses an open jealousy towards Mikuru and all the other members of the SOS brigade, because he has to keep a facade of his true personality to fit Haruhi's expectations of his, while the rest do not (aside of Mikuru's Obfuscating Helplessness). At points in the novels it's made pretty clear that Itsuki's finding it difficult to keep smiling, such as in volume 9 he's been unable to sleep well for a lengthy period of time due to constant closed space activity, appearing exhausted and using a rather forced version of the usual grin, which falls off if he isn't concentrating. What is he really thinking? Who knows, it's the one thing he doesn't really talk about. Probably.
To add fire to the fuel, in the eleventh novel, he cheerfully prepares to fight (and probably kill, it wasn't made clear afterwards) the novel's Big Bad. Note the word cheerfully.
"The Love Song of J. Alfred Prufrock" by T. S. Eliot: J. Alfred Prufrock attends parties and formal events to try to be accepted by his peer group but ultimately feels dead inside, and that he has never done anything significant with his life.
In Luke Skywalker and the Shadows of Mindor, Luke is subjected to a terrible vision of what it's like to live through the heat death of the universe; when he comes out of it he's... different. He becomes nihilistic and depressed, believing that love and friendship are just tools people use to manipulate each other, and that it's pointless to save anyone. However, he's still Luke Skywalker, and he makes the conscious decision to act exactly like he did back when he still thought life had value and meaning, in the hopes of Becoming the Mask, longing to believe the happy lies again. Eventually he does get out of that mindset.
The narrator of Langston Hughes' poem "Minstrel Man" is Depressed.
The Lord Ruler thinks he has claimed laughter and joy for himself. I'm disinclined to let him.
Count Leedway in The Mug and Spoon is so cheerful and fond of practical jokes that his army friends nickname him Jolly Joe and think he takes nothing seriously. It turns out that thanks to his parents driving the family into debt, he is destitute and constantly fears that some new tax might ruin him completely.
Shion of No. 6 is hinted at being this. He smiles constantly and is generally very cheerful and sweet but he's also hinted to have a suppressed Yandere side to him. Beware the Nice Ones indeed.
Frank Chalmers in Red Mars is somewhere between Depressed and Empty. Coming from a poor family, he's almost entirely consumed by his ambition to succeed. At one point he looks at his life and realizes that all of it is a facade created to impress his superiors, and that he doesn't really have a self.
A Spanish-language poetry, Reír llorando (To laugh crying, in case you needed more hints), is about a man who has everything he could want, but still feels empty and depressed, visit a doctor, who tells him to go see a famous comic named Garrick to cheer up. Then the man reveals he is Garrick and asks for another remedy.
Natsuki Subaru from Re:Zero starts to become one of these as the series goes on. Possibly even started out as one from the beginning. As the series goes on it becomes clear that his happy-go-lucky attitude is covering up severe self-doubt and depression from trying to save his friends only to see them die over and over again and regret with how he spent his old life on Earth.
The title character in Edward Arlington Robinson's poem "Richard Cory" is a male Stepford Smiler, a rich, elegant, successful man who is envied by everyone around him. His secret unhappiness isn't revealed until the last lines: "And Richard Cory, one calm summer's night / Went home and put a bullet through his head."
As a child, Safehold Prince Daivyn Daykyn of Corsiande experienced the loss of his father and older brother and spent just over a year as a hostage in a Gilded Cage alongside his older sister, aware that his life hung on a thread. Once he's rescued he doesn't seem overly affected by it, as scenes of him show a Cheerful Child. This continues into adulthood, where Daivyn is almost infectiously upbeat, but those closest to him note the little moments of melancholy he hides from the world at large. One character wonders if it's simply the scars of that old trauma, however faded, while his fiancee concludes it's actually Daivyn trying to reduce how much he's associated with his father, Prince Hektor, who was known as a crafty, conniving power-monger. The only thing his fiancee can't work out is whether or not Daivyn is doing this consciously.
Harold Lauder from The Stand becomes Unstable after he finds Fran's diary and goes crazy. He then starts smiling to hide the fact that he hates pretty much everyone, including himself. Another character later notes that when Harold is not smiling, he looks insane.
Certain chapters and episodes of Student Council's Discretion imply that Ken's happy-go-lucky persona is a defence mechanism to keep him from a severe emotional trauma from back in junior high, and not his actual personality.
Many of the characters in Tangerine fit this trope. The three most glaring examples are Joey, Erik, and Paul. Erik is probably the king of this trope.
The genuine people in this book are found by exiting suburbia (achieved by the middle school getting sucked into hell a sinkhole and the kids being spread out) and rubbing elbows with tangerine farmers like Luis Cruz, and other "real" people.
Aaron Armstrong being this is the whole point of "Three Tools of Death" by G.K.Chesterton. Discussed In-Universe by Father Brown: "Why couldn’t they let him weep a little, like his fathers before him? His plans stiffened, his views grew cold; behind that merry mask was the empty mind of the atheist." He committed suicide.
In Evgeny Zamyatin's dystopian tale We, the totalitarian government works towards making its subjects as machine-like as possible: perfectly scheduled and mapped lives, synchronized movements of multiple people, and lack of names in favor of numbers. This agenda is ultimately crowned by "The Great Operation" in which the human brain is irradiated by rays, that completely and irreparably strip a person of his imagination. One of the effects (aside from turning a human being into an obedient and ever-happy shell of a man) is a perpetual grin on the subject's face, as he now thinks "smiling is a natural expression of human face". In the end, D-503, the protagonist, is subjected to the Operation.
X-Wing Series: Ton Phanan, though you don't really get to see it until late. He's a Deadly Doctor, a Deadpan Snarker, caustic and funny and able to put aside the sarcasm in the right moments. He also feels that the cybernetics he started to get after almost being killed couldn't replace his future, which died.
Mixed Gender Examples
In A Christmas Carol's Bad Future sequence, both Cratchit parents are shown trying to be cheerful following Tiny Tim's death, with Mrs. Cratchit claiming that her eyes are only watering because it hurts them to sew by candlelight, and Bob warmly describing the green gravesite he's chosen for Tim. But finally Bob can't contain his grief and breaks down in tears, crying "My little, little child! My little child!" They reach a moment of genuine, if bittersweet happiness by the end of the scene, as the whole family promises to always remember Tim and to emulate his patience and kindness.
The Elder Empire: Nearly everyone at Candle Bay Imperial Prison, from prisoners to staff. At first, the smiling receptionist is kind of funny, as she is always perfectly professional and Calder always frustrated. Then he sees what's been going on in the prison, and realizes she literally has no choice but to smile.
Arguably the entire tree-dwelling Kindar culture in Zilpha Keatley Snyder's Green-Sky Trilogy. The descendants of a group who decided that humanity's past misdeeds were best forgotten, they consider negative emotions (lumped under the heading of "unjoyfulness") inappropriate and best kept suppressed.
Dee and James from The Hearts We Sold both qualify. Dee is the more obvious example, putting on a happy face whenever she visits home to avoid inciting further abuse from her father, but we later find out that a lot of James' silliness and adventurousness stems from the fact that he has a brain tumor.
Vincent and Carrie Raymond in Geoph Essex's Lovely Assistant are astonishingly warm and cheerful Beautiful People, though their plans to summon a galaxy-sized monster and destroy the world places them squarely as Unstable. Jenny even thinks about the Stepford effect by name. Jenny's friend Keith Heckler is also described with a constant smile and a completely amoral personality, even though he is one of the good guys, and when things get ''really'' serious, he does occasionally drop the smile.
Heckler didn't seem too bothered, though it seemed likely that Heckler had hunted down and killed his conscience in some tribal rite of passage when he'd smoked his first cigarette at thirteen. If any moral core remained, it was huddled in a dark corner of the attic in his mind, running a near-toothless comb through tangled thinning hair, rocking back and forth and mumbling eerie sing-song lyrics to forgotten nursery rhymes. That thought alone made Heckler's perpetually cheerful grin seem downright petrifying.
Nineteen Eighty-Four It is advisable to wear a look of quiet optimism when facing a telescreen, among fellow party members, anyone who might be a snitch or agent of the Thought Police, or just everywhere really. Indeed, an inappropriate expression at the wrong moment could constitute Facecrime, and facial tics and full-blown tourettes are apparently fatal.
The main cast of Jodi Picoult's Nineteen Minutes (Barring Peter, Jordan, and possibly Patrick)
Josie is Depressed, pretending to be the perfect Golden girl whilst simultaneously having to put up with an abusive boyfriend, neglectful mother, and niggling suspicion that if she stops smiling for even a second, everyone will realise she's nothing special.
Matt is Unstable, pretending at first to be the perfect boyfriend until he turns out to be an abusive jerk.
Alex has to act perfect 24/7 for the sake of her job whilst the strain tears her apart.
Lacy has to deal with the fact that one of her children turned out to be a druggie whilst the other (Peter) went on a killing spree.
Lewis (Lacy's husband) has to deal with the above whilst being a happiness economist (Meaning it's his job to work out the mathematical value of happiness)
Selena gets off relatively easy, only having to deal with racist idiots.
Then there is Cersei Lannister, who tries to run said court. Becomes especially evident in A Feast for Crows, when she becomes a point-of-view character.
In a somewhat unusual example there's Asha Greyjoy. Asha has managed to become a leader in a culture that completely believes in an extremely manly approach as being the right way to do things while thinking that all women should Stay in the Kitchen. As a result of this she is secretly afraid that any slip-up, mistake or failure will lead to her being forcibly removed from the position of authority she has fought to achieve, and she overcompensates and practices a tough girl catchphrase in an attempt to prevent anyone from even trying to do that.
Theon Greyjoy. Everyone comments on how he is always smiling or snarking, as if he hadn't a care in the world or knows something nobody else does. And, almost everyone is to some extent creeped out by it because he keeps it up even when it's grossly inappropriate and often downright morbid. Sure enough, he's got issues even he didn't knew he had, as a result of spending half his life in a situation where everyone maintained a polite fiction of him being a "guest" and ward when he was really a hostage to keep his father in line. In other words, all through his childhood and teenage years his life was constantly being implicitly threatened, and could be forfeit at any time if his notoriously stubborn and ambitious father attempted another rebellion against the crown, and he was supposed to pretend he didn't know all that. All things considered, it's probably not too surprising he turned out to be a complete basketcase.
Littlefinger seemingly has a particularly empty one. Sansa Stark, who has a pretty bad judge of character at the start of the series, notices that his eyes don't smile when his mouth does. It's not clear exactly what he is under it, but having the blood of thousands on his hands hasn't chipped his mask.
Varys too has a case of this. Like Littlefinger, it's implied to be more than just a mask to wear in public...
Daenerys Targaryen, during her wedding to Drogo. Despite her discomfort at the situation she's in, Viserys forces her to smile so her husband will notice her. She ends up smiling so hard her mouth aches, while shedding Tears of Fear.
In Soon I Will Be Invincible, the Champions are a cracking facade of glossy superheroism concealing bulimia, pain killer addiction, and the usual shenanigans. Twisted later when the apparent Bulimia and pain killer addictions turn out to be food allergies and life-sustaining medications in keeping with the "mundane lives of superheroes" theme.
Audrey Armat and her father Emilio in the mystery novel The Total Zone.
) also has its protagonist experience a telepathic vision of a Stepford Smiler's mental landscape. Or... well, it's a misogynistic idea of what CS Lewis imagines a woman's mind is like, very dull and materialistic and unappealing to him, with a vague dread to it, that has the protagonist despising her as shallow.