Primal Scene

"Kitty: "Oh! Oh, Red!" Red: "Oh, Kitty!""

- That '70s Show

Someone, usually a child, is wandering in his or her house and walks into two people having sex. (Because nobody ever has a bedroom with a lock on the door in fiction.) Most of the time it's the parents. This can be a trigger for A) the parents to give that one discussion we all mention vaguely, B) the unfortunate soul to be Shell Shocked for a while, C) be very funny or some combination of the three.

Its psychological term is the Primal Scene, coined by none other than Freud.

Naturally, media always plays this as a traumatic experience, rather than the person just figuring it is natural, quickly realizing it, or just not understanding why mommy and daddy are playing leap-frog naked (and then after looking back on it all, will quickly apply Brain Bleach to forget about it).

And of course, all 'child' characters, no matter how old, don't understand sex. Characters identified to the audience as 'teenagers' will simply be horrified. This rule applies to almost every example, despite the fact that most children (even 8-9 year olds) will know what they interrupted in Real Life

And remember, if it hasn't happened to you, it's probably happened to someone you know, heaven forbid.

See Caught with Your Pants Down for the single-player version; for the reverse scenario with parents walking in on their adult child getting frisky, see Parents Walk in At the Worst Time. A subtrope of Interrupted Intimacy.

Anime and Manga
""Why do you need to take your pants off every time?""
 * In Revolutionary Girl Utena, Nanami comes across
 * In Fushigi Yuugi, Suboshi catches his boss Nakago having sex with his dragon and lover, Soi.
 * In one of the databooks for Love Hina, it reveals Motoko's fear of turtles is derived from walking in on Tsuruko and her husband.
 * In Kuragehime:.
 * In Yosuga no Sora:
 * In Berserk, Casca, whose mind was reduced to that of a child due to some unfortunate events, walks in on Luca, her temporary prostitute care-taker, and Jerome, her Love Interest customer.
 * In Happy Yarou Wedding, Yuuhi keeps trying to cover these up as "wrestling" but the five year old Shouta doesn't entirely buy it.
 * In Happy Yarou Wedding, Yuuhi keeps trying to cover these up as "wrestling" but the five year old Shouta doesn't entirely buy it.

"Asuha: "Why are you two naked? I'll get naked too!""
 * In the manga Ooku, the young Tsunayoshi has a breakdown after discovering.
 * In Lotte's Toy!, Astarotte witnessed her mother doing This and That with a member of her harem when she was five years old. Needless to say, she's hated men ever since.
 * Subverted and Played for Laughs when Lotte and Naoya deceive Elika by pretending to do This and That. Asuha walks in on this... and joins them.

Comics

 * In Watchmen, a young Walter Kovacs walks in on his prostitute mother servicing a client. Unlike most instances of this trope, this is not Played for Laughs and is shown to be very Harmful to Minors, the behaviour of the adults involved plays a part too.
 * It wasn't so much the exposure to sex that damaged to him, but the fact that his mother insulted and beat him up afterwards for bothering her at "work".
 * It's implied that the most important thing was that he thought the man was hurting her, not understanding what they were really doing. He was worried about his mother, and then she beat him when he came in to help her.
 * The shadow he sees on the wall (two upright people joined together) is repeated throughout the book: In the grafitti Rorschach looks at, in the shadows on Rorschach's mask, in the dream Dan has of him and Laurie, and . Finally,.
 * In Runaways, when Gert finds out her parents are actually super villains, she says "This is worse than the time I walked in on them doing it!"
 * Robert Crumb once tried to explain such a scene to his son as him and Aline (his wife) playing horse-riding. He didn't find an explanation though for why Aline had to be naked to do this.
 * In Kick-Ass, Dave walks in on his father and his new girlfriend doing it doggy-style on the living room couch.

Fan Fiction
"I remember my parent's honeymoon!"
 * Happens in this Naruto fanfic, with the predictable result/s.
 * In the (not for faint-hearted!) Pokémon fic Latias' Journey, the cast enjoys a quiet-before-the-storm party on the night before the final battle. Some of them go for more...involved celebrations than others. So anyway, Phanpy walks in on Uncle Brother Pikachu going at it with a Weavile. Traumatized, he runs to Aunt Corsola for help, and walks in on her right in the middle of Crawdaunt's massive orgy. You can probably imagine what happens next.
 * In the Order of the Stick fic the Oneiroi Series, parents intentionally have sex where their child can see them, leading to this situation often. On the other end, Tiasal has walked in on her (more modest) parents an unnamed amount of times and has even seen her grandparents going at it, and she's demonstrated a surprising amount of nonchalance about the whole thing.
 * Due to a series of spoileriffic circumstances in Luminosity, Elspeth ends up with almost all of her parents' memories. After a person asks a question about how much she can remember, she thinks of the wrong memory, and...


 * Played With in a recent chapter of this fanfic-- Kyon's sister walks in on him and his girlfriend having sex. Evidently this happens so often that it no longer fazes her. Also, Mikuru (who in this fic is Kyon and Haruhi's future kid) knows about it, and is a bit shocked, even though she knew it had to happen eventually.
 * Toyed with in the My Little Pony: Friendship Is Magic fanfic Progress. Princess Luna's embarrassed enough to flee to a castle labyrinth and blush bright red after walking in on her roommate and roommate's boyfriend, but as she's old enough to figure prominently in the local Creation Myth and more than old enough to be aware of sex (if only in the theoretical sense), she attributes this reaction to her old-fashioned views. Then she has a particularly surreal nightmare about walking in on Celestia with Luna's Acabus, suggesting the matter to be much more traumatic than Luna is willing to admit to herself.
 * In chapter 4 of the My Life as a Teenage Robot fic My Life as a Teenaged Von Neumann Device, Sheldon freaks out when he walks in on Jenny and Brad after they've just had sex...
 * Played for laughs in a later chapter, where Tuck freaks out after walking in on Mrs. Wakeman pleasuring herself in the bathtub. And later still, when Tiff Crust walks in on

Films

 * In Reality Bites, one of the characters tells that this once happened to her.
 * Averted in Poltergeist, as Carol Ann's request for a late-night glass of water takes place when her parents are only engaged in foreplay, not intercourse.
 * In Rain Man, Raymond walks in on Charlie and Suzanna making love, and as he doesn't understand what's going on, mimics their orgasmic moans until Charlie realises he's in the room and snaps angrily at him.
 * Occurs in The Rebound when Sandy's young son walks in on her and Aram having sex on the living room couch. Hilarity Ensues. Not much mental scarring though.
 * A very dark version occurs in Orphan, when Esther catches Kate and John having sex over the kitchen counter.

Literature

 * In The Da Vinci Code, a version of this is the reason why the female protagonist had a falling-out with her grandfather . Not just Fan Disservice since the participants were elderly, but also rather Satanic looking.
 * In Memory, Miles has a moment of surprise when he realizes his Aunt Alys (widowed since shortly before Miles's birth) has started sleeping with his former boss, ex-Spymaster Simon Illyan. When Alys's son Ivan finds out, he has reaction B, and the reader gets a nice dose of reaction C from the interplay.
 * Unlike most instances of this trope, Miles and Ivan are adults. Ivan's reaction has more to do with: a) the fact that this is his mother we're talking about, and b) the fact that both Simon and Alys have public reputations for being extremely prim and proper (well, for Simon it's more "respectable" than "prim"), and what they're doing together is... not.
 * Robin in The Tomorrow Series mentions this was how she last saw her parents.
 * Briefly discussed in Head Count by Ingrid Noll: when Maya is in counselling after, she makes up a dream about being a little bird that flies around and looks into people's windows. Her psychiatrist assumes that she must have walked in on her parents as a child.
 * Norman Mailer's The Castle in the Forest has none less than a young Adolf Hitler being traumatised after walking in on his parents having sex in the 69 position.
 * Parodied in the Girl Genius novel Agatha H. and the Airship City: Young Agatha was traumatized by walking in on her "construct" foster parents recharging themselves.

Live Action TV
"My emotional journey began at 5 years old when I walked in on my parents having sex in a position my father would later playfully describe as "the jackhammer"."
 * A 1973 episode of The New Dick Van Dyke Show had this. When CBS refused to air it, writer-director Carl Reiner quit the series in protest.
 * Formerly named for the scene in That '70s Show in which this happens to Eric, with his parents yelling the quote at the top of the page. Donna reveals that it also happened to her when she was a kid - which she can recall vividly even a decade or so later.
 * Used more than once too, as later in the series, Eric casually walks into the kitchen, where his parents are playing an "adult" version of Marco Polo (don't ask).
 * The age-flip occurs in the episode about Jackie's lodge, where at the end of the episode Kitty and Red walk in on Eric and Donna doing the horizontal tango on the kitchen table. The next scene shows Kitty and Red scrubbing the table furiously to cleanse it, eventually deciding that it would just be best to get a new table.
 * In an episode of Sex and the City, Brady sees Harry and Charlotte having sex. Charlotte freaks out and calls Miranda, panicking and convinced that she has damaged the boy for life. Miranda is amused and explains to Charlotte that being a toddler, he doesn't even know where his nose is, let alone what sex is.
 * J.D. explains his emotional problems thusly in Scrubs:

"Ross: Mon? Mon, are you okay? Monica: Remember that video I found of Mom and Dad? Ross: Yeah? Monica: Well I just caught the live show."
 * On Desperate Housewives, Gaby and Carlos are having blind sex (he is blind; she's wearing a blindfold). Gaby hears a sound, rips off the blindfold and, lo and behold, there is Juanita drinking from a juice box. They don't know how long Juanita has been there, either.
 * Dawson from Dawson's Creek was constantly walking in on his parents having sex, at least in the first season. He also once saw the "preview" to some reconciliatory sex between them, but managed to sneak out unnoticed before "the main attraction".
 * Monica from Friends first found a video tape of her parents having sex (complete with "Oh Jack" and "Oh Judy"). Then a few episodes later she was hiding from her parents in the bathroom when both walk in, and, well, this quote pretty much sums it up:

""Why is Daddy hurting Mommy? Wait, he's not hurting Mommy, he's loving Mommy.""
 * In a later episode, whe she recounts this, Chandler mentions that he once walked in on his parents and a man having a threesome.
 * The Drew Carey Show. His response to a psychiatrist:

"Years later, I realised I had walked in on my parents having sex, and was appropriately disgusted. Back then, I was just glad they'd managed to make up so we could be a family again."
 * Then there's the time he walked in on his brother and Mimi having sex. He had his kitchen bricked off and his couch sent out to be exorcised.
 * In an episode of Oliver Beene, Oliver walked in on his parents doing the deed, but they placated him by claiming to have been playing some sort of game. The narration notes:

"Titus: Your dad isn't dead. Erin: Yeah, I know. Otherwise, what I walked in on my mother doing to him would've been so sick!"
 * In Six Feet Under, Nate's daughter Maya sees him and Brenda having sex and starts jumping up and down.
 * In the first episode of Titus, a misunderstood message causes Erin to walk in on her parents.


 * An episode of Ready or Not revolved around sexuality, beginning with Amanda walking into her parents shagging it out.
 * Torchwood has the adult version when Gwen walks in on Jack and Ianto. In a hothouse. Hilarity Ensues.
 * On Modern Family, Phil and Claire's kids walk in on them having sex which traumatizes both Claire and the kids. Phil tries to deal with it humorously. The family have an uncomfortable talk about it.
 * King of Queens Doug and Carrie look after Deacon and Kelly's kids at their apartment while they're out of town. One of the kids walk in on Doug and Carrie having sex and draws a picture of it.
 * In Sugar Rush, Kim finds out about her mother's affair with their home decorator when she walks in on them having very loud sex in the living room.
 * Referenced in this scene from Eastbound and Down.
 * In Thirty Rock Nancy Dononvan has given at least two different excuses to her children when they walked in on her. She comments to Jack that they walk in a lot, but doesn't specify how much "a lot" is.
 * In Mad Men, Sally Draper sees Given that she's pretty precocious (despite being only 12 or 13, she's more aware than the average girl her age, and ), she doesn't seem to be particularly scarred—merely astonished and kinda disgusted.

Video Games

 * Kana from Kana: Little Sister once catches her brother Taka and his friend Yumi having sex. Aaaaaawkward.
 * Or the other way around, with Kana and Taka being caught by Yumi. Up to Eleven awkward?
 * A funny machinima made with The Sims 3 milks this trope for all it's worth.
 * In Psychonauts, it is revealed that as a kid, government agent Sasha Nein read his father's thoughts to see what his Missing Mom was like. It doesn't end well.
 * A pretty tragic example, seeing as he was just remembering the woman he loved and it causes Sasha to freak out so badly he runs away from home.
 * You Don't Know Jack: The Ride includes a question, based on the idea that Steven Seagal movies all have three syllables (Under Siege, Hard to Kill, et. al.) and asks the contestant(s) to identify the likely plot to a Seagal movie named Primal Scene (the correct answer, of course, being the outline of this trope). At the end of the round, players are treated to someone impersonating Seagal's voice and acting style and blandly exclaiming, "Oh no, mom and dad are wrestling!"

Web Comics

 * It happens (NSFW) in Sexy Losers (the strip is even titled "Primal Scene"), and being SL, it wasn't your garden-variety sex...
 * This strip from the Magical Girl Lyrical Nanoha Strike Out Fan Web Comic by Entropy Max.
 * Happened to Faye from Questionable Content.
 * Marten is apparently fine with his professional dominatrix mother describing her sessions with clients. But if she's talking about his dad...
 * Hilariously subverted in Niels when Kiddo walks in on this.
 * An early Kevin and Kell had Rudy walking in on the two titular characters doing some roleplaying.
 * Nip and Tuck: "My eyes are burning...", and apparently it wasn't the first time
 * Seems to have happened off-strip, but little Scarlett from Plus EV knows about the game that only mommies and daddies can play. See here.

Web Original
"Ness: Everything...I could hear...everything...they were thinking! Poo: Oh, the poor child."
 * In the flash film Nin10Doh! by 'Kirbopher', Ness walks past a porno theater. Being psychic, he is reduced to a quivering wreck on his bed.

Western Animation
"Lois: Now, you shouldn't be frightened, Stewie. What you saw was actually a very beautiful thing. Stewie: Evidently, madam, you and I differ greatly in our conception of beauty."
 * The Simpsons had it in a Flash Back to Bart's first words. He's walking down the hall and sees Homer and Marge fooling around, to which he says "¡AY CARAMBA!" For obvious reasons, Marge thought it better not to bring it up.
 * Also happens in "The Haw-Hawed Couple", when Bart and Lisa walked in on Homer and Marge 'Snuggling', despite the boombox playing the fake argument tape Homer and Marge made, leaving Bart traumatized.
 * Until he gets some perspective from Milhouse: "Trust me, Bart, it's better to walk in on both your parents instead of just one of them."
 * Family Guy - "The Son Also Draws":

"Jackie Gleason: Pow! Right in the kisser!"
 * There also the episode focusing on Lois's brother, Patrick, who as a child saw his mom having sex with Jackie Gleason. As a result he went crazy, was shipped off to a looney bin (at a young age no less), and developed a hatred for obese people. So much so he goes on a murder spree when Lois temporarily releases him ('course Peter's idiocy is also to blame).

"Peter: Opie's right there. Lois: I want him to look, Peter. (Opie runs away in terror)"
 * A variant is the one where Peter & Lois decide to have sex in his office.

"Kyle: Dude, it's a lady getting pooed on! Stan: Whoa, is it Cartman's mom? Cartman: Oh, very funny! Kyle: Hey, it IS Cartman's mom!"
 * Opie is severely mentally handicapped, which makes this all the more traumatizing.
 * Considering that a later episode shows Peter and Lois engaging in BDSM and another shows Stewie's "sexy parties", it may well have been something legitimately traumatizing.
 * King of the Hill had Hank walking in on his elderly mother and her new boyfriend having sex on his dinner table. He goes temporarily blind as a result.
 * Nearly happens in an episode of South Park, when Eric Cartman, who believes he is dead, hears his mother thanking the plumber and believes she is wailing in mourning over his death.
 * There were quite a few times when Cartman is exposed to his mother's oft-mentioned promiscuity, though usually through seemingly blank video tapes.
 * The most memorable example for Cartman doing this likely came from The Movie, when the boys are on the internet and stumble on a porn video (apparently filmed in Germany).


 * Invoked in the American Dad episode "I Am the Walrus"; Steve is trying to usurp Stan's role as the Alpha Male of the house, so Stan tricks Steve into walking in on him and Francine being intimate. After brutally averting Not What It Looks Like, he tells Steve that the fact that he mates and Steve doesn't proves he's still top dog.