But you don't know Karen by night."
Get Alice home to her significant other, however, and well — the blouse is going to be on the floor, the skirt in the hall, her hair all over the place... and the rest is too NSFW even to describe. As strait-laced as Alice may be in public, none of that carries over into her private life — and vice versa.
- In a way Nyamo-sensei of Azumanga Daioh. While she's generally straight-laced and down-to-earth in contrast to Yukari, the one who you'd expect to have a wild social life, Yukari makes a comment about her Nyamo "not being alone" in a previous summer, and Relaxo Vision or not, the hilarious incident where she gets drunk and gives The Talk implies she's fairly experienced.
- Code Geass: Nina Einstein and the infamous table scene. Nunnally actually wheeled in on this, but fortunately she was already blind and (hopefully) too young to properly...interpret any of the sounds she might have heard.
- In the manga Crimson Spell the protagonist Valdrigr is under a curse that causes him to turn into a rampaging demon. The trope kicks in when the Halvir, wizard Vald has recruited to help break the curse, decides that the best method of quelling the demon's rampages is to have sex with him - after the first few instances, it becomes clear that demon-Vald is increasingly less interested in violence and more interested in getting it on with Havi.
- Golden Boy:
- Naoko, the second episode's Girl of the Week, seems to play the part as the daughter of the mayoral candidate whom Kintaro has joined the campaign staff of. In truth, she is a Covert Pervert who attempts to seduce Kintaro at every turn in both public and private.
- Reiko, the fifth episode's Girl of the Week, seems to be a Yamato Nadeshiko given that she hails from a traditional family. However, she harbors a secret wild side in that she is a Biker Babe who literally gets off with her motorcycle as she thinks that no man could not satisfy her. Kintaro catches her in the act in the episode's Cold Open, and later on when he follows her into an abandoned building and puts two and two together, she drops the façade and proceeds to give him a show by pleasuring herself on her motorcycle while completely naked.
- In the ecchi manga My Balls, the main character's primary love interest Minayo is a sweet, kindly young woman who works at a daycare center. When she gets drunk, however, she goes into what the protagonist describes as "full-blown nympho mode". Unfortunately, said protagonist can't have sex for a month or the demon sealed inside his balls (hence the name of the manga) will be released and cause The End of the World as We Know It. Minayo happens to be an alcoholic, and Hilarity Ensues.
- Paprika: Straight-laced Chiba becomes a lot more flirty and extroverted when she turns into Paprika.
- Paranoia Agent has an episode that plays with this. Harumi Chono is a quiet, conservative, mild-mannered school teacher by day, but at night her other personality takes over—Maria, a popular prostitute. When Harumi gets engaged, she starts trying to desperately get rid of Maria before her wedding day, which causes Maria to fight back.
- Sprite: Between Two Worlds, wherein Manami, a severely repressed and meek college student turns into Nami, an outrageously uninhibited flirt whenever she's put into any situation that is too much for her to handle. The catalyst is her cousin Toru, who convinced Manami to be more confident around him when they were young by convincing her she was really Nami.
- A Hentai Manga take on this: WereSlut (unfortunate name created from whole cloth by Eros Comix, the US distributor) is about a shy college student named Kimiko who takes a magic beauty pill to make her attractive enough to win her childhood friend (read: she takes off her glasses). It works, but, due to the magic pill being past its expiration date, it keeps kicking in whenever she gets aroused. After the first time, though, it also kills all her inhibitions.
- The Firesign Theatre's "Forward Into the Past" sketch, which parodies old-time radio, announces a show called "Captain Equinox". The main character is described this way:
By day, Adolf Tree, a mild-mannered college professor!By night, Kiki, a mini-skirted habitué of Hollywood's starstruck Sunset Strip!But twice a year he's...CAPTAIN EQUINOX!
- Aurora was like this in Alpha Flight's early years, exaggerated by her Split Personality. One persona was Jeannie-Marie: strict, stuffy schoolmarm teaching at the same girls' school she was raised in. And then there was Aurora: sultry, adventure-loving, free-spirited partier.
- While it never came up in the comics, writer Mark Waid's character notes for the Fantastic Four speculate Susan Storm was like this as a young woman to cope with the stress of having to raise her little brother.
- In Quantum and Woody, Amy Fishbein appears to be a prim and proper white-collar professional, but she starts dropping Anvilicious innuendos and undressing herself as soon as she's alone with Woody.
- More than one My Little Pony: Friendship Is Magic fanfic has portrayed Fluttershy like this.
- A Pleasant Surprise paints her as being quite assertive and forthcoming with her sexuality to the point of outright seducing the protagonist.
- Blissful Dream is another such story. Here, Fluttershy is shown as being sexually dominant over her lover.
- Advice from Pinkie Pie puts Fluttershy in a BDSM relationship — as the dominant one — with Rainbow Dash ("Now, my little pony… you're going to love me."), while in My Little Slave, she initiates a rape-dungeon roleplay that lasts for 29 chapters before the reader finds out the truth.
- Morning Glory downplays it, as she's embarrassed afterward even in private, but she didn't need the Apples' "honeymoon cider" after all to go wild with Big Mac — she left it for Applejack and Rainbow Dash's unwitting use.
- Always the Quiet Ones: The Rainbooms come to a horrifying conclusion that Fluttershy might be a Serial Killer. Turns out in private, she is in a bondage relationship with Rainbow Dash.
- Celestia, Luna, and Cadance all show this to varying degrees in Diaries of a Madman.
- In A Pikachu in Love, Pikachu is worried that this is what Ash and Co. will think if they catch him sneaking off at night to meet Pichi, and doesn't want them drilling him for questions on the matter. That still doesn't stop Misty from finding out, though she doesn't press the matter and keeps it a secret from the others even after the ending.
- Rapunzel in The Secret Life of Punzie started committing minor acts of rebellion in-secret due to being sick of being the A+ good girl, starting with getting a tattoo. Eventually it culminated in Rapunzel becoming the star dancer in a lesbian strip-club.
- The title character of the Sexploitation film Angel (1984) and its sequels in The Angel Trilogy. The tagline for the original movie was "High School Honor Student By Day. Hollywood Hooker By Night".
- The movie Belle de Jour is about a seemingly average housewife who's a prostitute in secret. But here this trope is inverted: as she is a housewife, she can actually do this job only by day instead of by night. (This is where the name of the film comes from.)
- Somewhat subverted in the film Blind Date where Walter's sister-in-law tells him not to let the date get drunk as she goes wild. This information is relayed to him via his brother who adds lots of leering to the information. Cue the man getting his date, Nadia, drunk, to find that she goes wild in a drunk-driving, crash-the-car, ruin-the-evening way.
- This is a source of some confusion in the film Desperately Seeking Susan.
- Flashdance: Zigzagged. Alex spends her days visiting a retired ballerina and working as a welder while dancing at a cabaret at night in font of a lusty male audience and the same is implied to be true for her friends. However, the girls seem to focus more on the art of the dancing than the sleazier parts, and it's technically a second aspect of their professional lives.
- In Guilty of Romance, Mitsuko is a professor at a university during the day and a prostitute by night.
- Jawbreaker: The lie Courtney wants to use to explain how Liz was murdered was that she was killed by one of her many lovers, who just got a little too rough one night. Since School Idol Liz's reputation was spotless, Julie says no one is going to believe it. Courtney argues that is precisely the reason why.
Courtney: They'll believe it, because it's their worst nightmare. Elizabeth Purr, the very picture of teenage perfection, obliterated by perversion?
- Looking For Mr Goodbar is a very dark example. Diane Keaton plays a teacher of deaf children from a conservative Irish-Catholic upbringing who starts out having an affair with a married college professor, then starts cruising seedy bars for one-night stands that grow progressively more degrading and dangerous, culminating in her getting raped, beaten, and stabbed to death by a troubled Vietnam vet.
- Lost Girls and Love Hotels: Margaret is just an ordinary English teacher during the day. During the night, she's getting drunk or having sex in love hotels with men.
- My Super Ex-Girlfriend: Vaughn thinks Jenny is this on first seeing her, saying that though she looks like a librarian on the outside, inside there's a wild side. He's more right than he knows. As her Super Hero alter ego G-Girl, she's revealed to be a very enthusiastic lover she accidentally injures Matt and destroys his bed with her Super-Strength.
- In Sideways, former soap star Jack woos a fawning, plus-sized waitress while at dinner, who comes across as Adorkable meeting a celebrity crush. It turns out she has a quite freaky side, not only engaging in anal sex with Jack hours after meeting him, she and her husband then have a long, wild sex session over her husband catching her and Jack in the act.
- Slumberland: The scantily-clad salsa dancer Flip dances with is, in the real world, a nun who's having these dreams while she'd fallen asleep while praying inside a church.
- The red-headed librarian from Tomcats looks like a plain, uptight young lady. She (and her grandma!) are also into S&M.
- A relatively tame version occurs in Good Omens. Sweet little old lady and part-time medium Madame Tracy also offers appointments for "strict discipline and intimate massage every evening except Thursdays", and there are hints that she goes a little further than that on Thursdays.
- Erika Kohut in The Piano Teacher by Elfriede Jelinek is a very unhappy example. Her oppressive mother has totally managed to suppress her natural sexuality, so she tries to make up for it by secretly and obsessively pursuing weird, unhealthy perversions, though she can still barely feel anything. When she gets into an affair with her student, he soon gets freaked out by her tastes.
- In Saving Zoë, Teresa is a pretty preppy girl who acts and sings. By night, she hangs out with drug dealers and porno producers. The same could be said about Zoe, who seems like a perfect bubbly girl but smokes drugs and has sex when her parents don't know. This tendency leads to Zoe's death.
- The essence of The Strange Case of Dr. Jekyll and Mr. Hyde. Jekyll is an upstanding citizen by day, but he becomes Mister Hyde by night in order to live out his immoral, sadistic fantasies without being recognized.
- The Torchwood novel SkyPoint takes this to extremes; a very prim and proper little old lady, who is actually an S&M prostitute.
- Almost every Cairheinan noblewoman in The Wheel of Time is heavily implied to fit this trope. Though during some festivals they will run around almost nude on the streets, especially during the Feast of Light (during which normal prohibitions against inter-class kissing (and other things) are lifted), leading to a large number of commoners having bragging contests about who made out with the most important noblewoman.
- ONLY during the Feast of Lights, after which any such incident is ignored by all parties. With Cairhien being partially based on Versailles France, this roughly corresponds to Mardi Gras.
- Angel (or rather, his evil side Angelus) hints that cute geek girl Fred is like this.
"Ah, Fred. You look all fresh and sweet, but I hear you at night in your room with Gunn. The things you say. I'm lying there, listening, hands under the covers... I can't help myself. It's so... gripping.
- The Murders: Kate is a reserved and professional detective who it turns out often has BDSM sex with Pete when off duty.
- The Victim of the Week in the Murdoch Mysteries two-parter "Stroll on the Wild Side" is a quiet librarian, but the autopsy reveals she has a rose tattoo on her ankle, which is not something a respectable woman in 1900s Toronto would be expected to have. It turns out she's been picking up men in a seedy tavern, apparently just to add some excitement to her life.
- On the Buses long-suffering Olive would love to be Naughty By Night, but her miserable husband Arthur would rather sleep. Actually, he'd probably rather do his taxes...
- Subverted on Person of Interest where a PoI is a dedicated workaholic doctor but seems to spend her nights going to night clubs and picking up men. However, a more detailed investigation reveals that she is actually stalking the man who raped her sister and caused the sister to commit suicide. The doctor is simply building up her resolve to murder the man.
- Reno 911!. Deputy Weigel and her boyfriend Craig both appear to be socially-awkward nerds, but what we see of their sex life is quite... adventurous. Subverted in that Craig turns out to be a serial killer.
- Sheila from Shameless (US). By day she's a sweet agoraphobic and germaphobic housewife. But at night she is very very into pegging filthy alcoholic Frank.
- Effy from Skins: innocent schoolgirl by day, Fille Fatale by night.
- Twin Peaks — Laura Palmer is a normal high school girl by day, but a prostitute at night, among other things. Or, as she says in The Movie, "Night time is my time."
- The Umbrella Academy: Sloane's very sweet and slightly shy in public. While with Luther though she has no compunction about having sex with him on the ceiling by use of her gravity powers.
- The Good Charlotte song Like it's her Birthday has this as the main theme — the Protagonist thinks his Girlfriend's cheating on him when she lies about where she's going, so he follows her and...
"Tonight I kinda get the feeling my girl is up to something
Something that is no good
She said she only had a meeting but she is dressed for something
Something that is no good
Now I'm not saying that she's cheating, but seeing is believing.
Can't believe it, what I'm seeing when I stepped inside."
- Halestorm: The song "Mz Hyde" is all about how the singer revels in this trope.
In the daylight
I'm your sweetheart
Your goody-two-shoes prude is a work of art
But you don't know me
And soon you won't forget
Bad as can be, yeah you know I'm not so innocent.
- "Gangnam Style" by PSY describes this as the singer's ideal girl. The translated lyrics:
A girl who is warm and humanly by day
A classy girl who knows how to enjoy the freedom of a cup of coffee
A girl whose heart gets hotter when night comes
A girl with that kind of twist
- The viewpoint character of Amy Rigby's "Wait Til I Get You Home" is shy — but she knows what she wants:
You make me so happy
But there's all these people around
So wait til I get you home
And the walls come down...
- Usher's song "Yeah!" includes the assertion "We want a lady in the street, but a freak in the bed".
- The song "Miss Byrd" from Closer Than Ever is about a secretary exulting in how no one who sees her would think that she's anything but "that dull Miss Byrd," yet she has secret trysts with her superintendent.
- Fantine in Les Misérables is fired from her factory job when she is discovered to have a child, and her fellow workers claim that she is a prostitute. However, she had only ever had one lover, who had abandoned her, and it is only after she is fired that she has to become a prostitute.
- The play Miss Julie fits this with regard to personality, but replace "librarian" with "aristocrat".
- Parodied in The Music Man: The town gossips manage to convince the Professor that Marian the Librarian is Naughty By Night primarily because she reads "racy" books by "Chaucer...Rabelais...Balzac" and was kind enough to befriend the town outcast. She's not, but he falls in love with her anyway.
- Possibly Litchi from BlazBlue. Despite her incredibly skimpy battle clothes, her personality is fairly conservative. However, supplement materials and a couple of gag endings say that when she gets drunk she gets rather...insistent.
- Jet Force Gemini: Running a mine in Rith Essa with his brothers isn't the only job Fishface has, it's only the one he has publicly. Later in the game, he can be found working as an emcee in Ichor's exclusive Big Bug Fun Club, where Juno and Vela can talk to him to request a song from a selected list.
- Leisure Suit Larry 7: Love for Sail! got this one, cranked up to 20, with Hot Librarian Victorian Principles.
- You Don't Know Jack Movies parodied this one for one of the Question 18 segues:
Question 18: Honor student by day... stripper by night!
- Nekoko from Yume Miru Kusuri though this is more of drug effect.
- Veronica from Daughter for Dessert is a respectable businesswoman by day, but sometimes, she is willing to get sexual in a dark alley with a guy she just met.
- Double Homework:
- Ms. Walsh is prim and proper in the classroom, but she is seen dancing sensually at nightclubs, and has cybersex with strangers on the internet.
- Lampshaded regarding Johanna and Tamara by Tamara herself:
Tamara: You’re a freak. I’m a freak. Johanna’s a freak.
- CollegeHumor: In "The Six Girls You'll Date in College", there's 'The One Who Goes to Church', who's easily impressed by the Nice Guy Audience Surrogate, and (with her modest attire and seemingly naive nature) seems out of place at the frat party where she meets him, but in the bedroom, she is not the naive virgin she appears to be, and is apparently heavily into bondage.
- The illustration for SCP-2076 shows an instance of SCP-2076 trying to use its infohazardous effect to convince the reader to have a secret life in the Furry Fandom like the clean-cut police officer pictured.
During the Sunday, he is Officer John.During Hanukkah, he is Spix's Macaw.Join the animalesque cross-dressers.
- In Futurama, a prim bureaucrat is utterly turned on after hours by Fry's horrifyingly slobby lifestyle.