This is when a character not known for their sexual prowess acts differently enough (usually more cheerful or mellow) for other characters to notice and question it. They (and sometimes the audience) find out that it is because said character somehow got laid.
(Alternatively, they'll go through the Did You Get a New Haircut? routine.)
Compare to Virgin Vision, where another person can tell a character has had sex without any clues being given off, and Virginity Flag, where there is a blatantly obvious sign of the loss of virginity. See also Sex Dressed and Sexy Shirt Switch.
- Gundam 00: Chaste Hero Setsuna asks his teammate Lockon "what are Allelujah and Sumeragi doing next door?" in the CD drama.
- In Junjou Romantica, Miyagi teases his collegue Hiroki about this a few times, once just to watch him squirm.
- Bakemonogatari: Araragi is seen in what one might call an exuberant and joyful mood. It's difficult to confirm that anything really did happen the previous night, but he does seem awfully happy.
- Implied in Ergo Proxy. After a certain point in the plot Vincent and Re-l start acting a lot nicer to each other. This is never explained.
- School Days: While never asked, Taisuke has this expression in a certain episode. This being School Days, that's because the night before, he indeed had sex, or rather, forced himself on Kotonoha while she was shocked at knowing that Makoto chose Sekai for his Folk Dance partner. She coldly dismissed him the day after and Taisuke is none the wiser that what he had done is basically rape. Did we mention this anime is a Dysfunction Junction?
- Gravitation: Played with/inverted. The night after Shuichi first has sex with Yuki, he walks around with glowing eyes and an enormous smile, asks his best friend to ask him what happened last night, and then won't specify.
- Haruhi Suzumiya: In the tenth novel, when Kyon is acting more cheerful and upbeat than usual, Taniguchi mutters "What's with you? Don't tell me you and Suzumiya finally...no, never mind." Considering that he makes no secret of the fact that he assumes the two are dating, it's pretty clear he thought they had their first time when he wasn't paying attention. They didn't.
- During the first flashback arc in Cavalier of the Abyss, Jae Hyuk is seen passionately kissing Serin on top of a bed. The next morning he's incredibly cheerful, even commenting about how great the weather is in the middle of a thunderstorm, leading to his Living Weapon Diffor, who had a crush on him, to call him out on this.
- In Ouran Highschool Host Club, the hosts walk in on Tamaki and Haruhi while Tamaki is helping her with her fear of thunderstorms. At the moment, he's putting a blindfold and headphones on her to assure that she won't hear or see anything. Needless to say, they assume that it's something else.
- In Natsu e no Tobira, Jack and Linds end up finding out about Marion losing his virginity to Sara when they go to her house to see if he's around and... find their friend only in a towel there.
- Shimoneta: Zigzagged in chapter 10, when Ayame walks in on Tanukichi and Oboro in the girls' locker-room and sees Tanukichi has pinned Oboro on the floor. Then sees Oboro is breathing heavy and smiling with a faint blush from just having his first orgasm. Ayame doesn't say a word, but clearly thinks she's interruptingnote so she ducks back outside and slams the door behind her.
- In Astonishing X-Men, after Kitty Pryde and Peter "Colossus" Rasputin finally consummated their relationship, they go to the kitchen together in high spirits, only to be surprised by the presence of Kitty's Big Brother Mentor Wolverine. Logan simply looks back and forth between them and says "'Bout time." Logan has super smell among his Super Senses and almost certainly caught the whiff of afterglow.
- A Superman story from the 1970s, Who Took the Super out of Superman has Lois Lane visiting Clark Kent's apartment and cooking him a beef bourguignon dinner, before having a romantic night together. Lois goes into work at the Daily Planet the next morning and a coworker, Steve Lombard, notices her acting unusually. It's ultimately ambiguous whether or not Clark and Lois actually did sleep together. The Superman fandom has turned beef bourguignon into something of an in-joke. Occasionally, beef bourguignon will also appear as a Mythology Gag.
- In For Better or for Worse, when Elly's friend, Connie finds out her dog Sera had gotten out and had been with the Elly's dog, Farley, Elly tries to be optimistic and suggest that maybe nothing happened. Connie doubts that noting that this is the first time she's ever seen a dog "smile". Sure enough, Sera ends up having puppies.
- In a Code Geass fanfic In the End, Lelouch is in a really good mood after losing his virginity to C2.
- In Crazy Little Thing Called Odd by bottoms up, the students realise that Snape is in a ridiculously good mood every time Harry has had detention with him. They just don't realise why that is. Hilarity ensues.
- Athena Prime had a Knights of the Old Republic fanfic where HK-47 pulls this trope in regards to Revan and Carth.
HK-47: Extrapolation, Master: The commander meatbag exited your bunkroom with a smile on his face, and you are presently unclothed, your body temperature is higher than normal, and your facial read-out falls in the range termed as 'flushed.' Do you require some post-coital refreshment?
- In One Thing Leads to Another, Robin and Starfire come to the common room after their first time. Among their teammates, one is an empath, the other is a shapeshifter with an enhanced sense of smell. They are quick to do the math.
- Subverted in the Tengen Toppa Gurren Lagann fanfic The Spiral Path. Everyone assumes this with Rossiu and Kinon, but the author notes go out of their way to point out that there wasn't any sex.
- Happens frequently in Teen Wolf fics. Because in Canon, werewolves have a much better sense of smell than regular humans, most fans agree that they would presumably be able to tell that someone has recently had sex by scent alone.
- In the Homestuck fanfic Like Lovers Do Aradia manages to not only tell that Eridan and Feferi have pailed, but also to convey her smugness about it without saying anything in particular.
(at breakfast the morning after)Aradia: In a good mood, aren't we. Slept well?Aradia: That it is.Narration: In the meanwhile, Aradia just finishes washing her cup and goes upstairs without any other comment. And that’s pretty much it. You’re sure she knows, she just doesn’t give a damn about it.
- In chapter three of Bait and Switch (STO) Captain Kanril Eleya strolls onto the bridge after having a one night stand while ashore at Deep Space 9. Her first officer spots it immediately and gives her a look.
Tess Phohl: What do you mean, ‘what,’ Eleya? You walk in here looking like a grayth that just dined on prize alicorn and expect nobody to notice?
- Luna immediately figures this out, by picking up on Celestia's good mood and the spring in her step in TD the Alicorn Princess.
- In Empath: The Luckiest Smurf, Duncan McSmurf is able to tell through his sense of smell whether a fellow Smurf just had "the Smurfette dream."
- Doing It Right This Time: In Chapter 3, Ritsuko is looking ridiculously cheerful and sporting a huge hickey. Misato tries to work up the nerve to ask the obvious question... And then Maya walks into the room sporting a collar, which answers questions Misato didn't want to ask.
- In chapter 8 of Advice and Trust Rei manages to piece together that Shinji and Asuka were just having sex in a supply closet based on how they smelled, their lack of tension, and the fact that they arrived back at the classroom at the same time even though they left separately. By extension, she's able to figure out that they've been in a Secret Relationship for the past few months (something that nobody else noticed) even though she had less than a month of experience with recognizing social cues.
- A Crown of Stars: In chapter 44, when Daniel greets Shinji and Asuka he notes that they seem very pleased and asks if they got any sleep the last night. Shortly after Ching asks Asuka how good Shinji was. When Asuka asks if they are so obvious, Ching replies that they're practically glowing.
Daniel: And you two seem like you passed a very pleasant night. Get any sleep?
Asuka: (thinking) 'Oh Gott, is it written all over my face or something?'
- Victoria, in the Dragon Age: Inquisition fanfic All This Sh*t is Twice as Weird, knows that Mahanon is setting up his Grand Romantic Gesture for Cassandra. When she wakes in the morning and finds that his bed wasn't slept in, she figures out what happened; when he comes back to the room a little while later, she proceeds to razz him as only an honorary little sister can.
Victoria: (sing-song voice) Someone never came to be-ed...
- Alluded to in The Apprentice, the Student, and the Charlatan. Trixie's first appearance sees her teasing Twilight over apparently getting laid with Nova, due to the fact that she seems like she's in a lot better mood than usual that particular morning, not to mention the way she was looking at him, though it turns out it's just because it's the first proper night of sleep she's had in months.
- (In)famously in Gone with the Wind, when Scarlett wakes up singing after a night of semi-consensual sex with Rhett.
- Every Which Way But Loose: Slowly pieced together by the main character's sidekick. Initially, he thinks their literal Team Pet just mated.
- The Brazilian movie A Mulher Invisivel has a line that goes like "You're too happy. Are you screwing someone?". He... kinda is.
- In Ten Inch Hero Jen, who is a virgin, masturbates for the first time. Later:
- Priestly: Hey, Jen, did you do something different with your hair?Jen: No, why?Priestly: I don't know. You just look different.
- In Turner & Hooch, when the normally uptight Turner tells his workmate to relax, the workmate suddenly proclaims, "You humped the vet!"
- In Sliver: "You have been fucking your brains out!"
- In The Specials, Deadly Girl is a bit more upbeat than usual and Minute Man is looking a little more relaxed. Ms. Indestructable takes one look at them and blurts out "Did you two sleep together?!" Deadly Girl wryly asks if oral sex counts, then cheerfully announces "Doughnuts for everyone!"
- In the 1987 Dragnet movie, after rescuing a would-be Virgin Sacrifice, Friday consistently refers back to it whenever he mentions her name. Until the very end:
- Streebeck: [catches Friday yawning on the way into work] Long night last night partner? I thought the Christian Science Reading Room closed at ten.Friday: Not that it's any of your business, Mr. National Enquirer, but I had the pleasure of spending a quiet evening in the company of Connie Swail.Streebeck: Wait a minute. "Connie Swail?" Don't you mean "the virgin Connie Swail"?[Friday merely turns his head and looks at Streebeck with a smile, accompanied with a *BUM-BA-DUM-BUM!* ]
- A couple times in Mallrats, other characters comment that Brodie is "glowing" shortly after he had elevator sex.
- In Starfighters of Adumar, Wedge, the leader and responsible type of Red Flight, reconciles with his old love interest Iella Wesseri. The next morning he is exuberant, a little flighty, and joking readily, while his Wing Man, who normally is the one with all those traits but spent the night on the balcony watching for attackers, is grumpy. It's never said outright, but the scenes do imply that Wedge and Iella had sex, and Wes almost-but-doesn't-quite ask him.
- In Alex Sanchez's Rainbow Road: "You two sure are smiley today. Did you finally bone last night?"
- After a night with Morelli in Four to Score, Stephanie Plum has to deal with Connie, Lula, Vinnie, and Ranger all commenting on her suddenly active sex life as soon as she's in the same room with them (and she didn't tell any of them).
- Traci Harding's The Ancient Future Trilogy: "I know that walk. That's Teo's 'I just got laid' stride."
- Paul Robinson's Instrument of God: Supervisor 246 recounts his first time with a woman as another teenager shows up. "‘Look, I'd better go,' I said, and I tried to walk past him. Well, I guess her boyfriend could smell it on me, because he said, ‘Did you just fuck her?' I probably should have just lied, and said ‘no,' then left. ‘Yeah,' I said."
- In Tom Clancy's Clear and Present Danger, the FBI director's secretary starts a relationship with a drug lord's intelligence agent and when she goes to work the next day, her coworkers notice she has "a sparkle in her eye that could not be hidden."
- Clancy did something similar with Executive Orders: President Ryan's Secret Service detail can tell that he and his wife had sex the night before by the way the two are holding hands.
- Honor Harrington: After Honor sleeps with Paul Tankersely, her admiral notes that "dinner agreed with her".
- In The Pursuit Of Happyness, by Douglas Kennedy, Sara's brother Eric knows that she slept with Jack, the guy she met at Eric's party.
- In one of the Alien Nation books, Sykes tries to have sex with an alien, leaving him with bruises on his neck from her legs; the aliens become very "uninhibited". While humans generally don't know enough about Tenctonese physiology to figure out what happened to him, his coworker is an alien too. He rehearses lying to cover it up. The moment he enters the workplace, another alien says "did you copulate with a Tenctonese last night?" Sputtering, he tries to run off, with the alien shouting behind him "sexual ignorance is dangerous!" Meeting his coworker only leads to more awkwardness (as his coworker knows his alien girlfriend). An almost identical scene, following almost identical events the night before, occurs in the TV series.
- The Sound and the Fury is this trope played seriously. Caddy's loss of her virginity is an obsession within the Compson family, with each of the members having a different reaction to it. Her special needs brother Benjy can even smell that something's changed about her after her first time.
- The Tough Guide to Fantasyland tells you the signs to look for in one of your tour members and the correct etiquette for the situation.
- Song at Dawn: Everyone can tell that Dragonetz and Estela have had sex because their love ballads are suddenly much better.
- A more subtle example in The Lost Fleet. After the first time Victoria Rione seduces John Geary, both of them come to the Dauntless's bridge, where Captain Tanya Desjani takes one look at them and instantly figures it out, despite Geary trying to act normal, and Rione being a politician (i.e. can easily fake any expression). Desjani makes a suggestive comment and leaves the bridge. Dumbstruck, Geary mouths "How?" to Rione resulting in a "need to know" speech, which Geary interprets as Women's Mysteries.
- This scene becomes Hilarious in Hindsight a few books later when Desjani develops feelings for Geary herself.
- Buffy the Vampire Slayer: Xander does this to himself in the middle of a very weird night. The best part is that no one else figures it out.
Lorne: Jeez, keep your pants on! (Angel enters) Well, I see we're a little late with that advice.
- This happens a couple of times between Angel and Wesley. In a season 2 episode, Angel demonstrates his Super Senses by remarking that Wesley had sex with a bleached blonde the night before. In season 4 during his Angelus turn, he mentions in front of the whole gang that Wesley has been having sex with Lilah.
- Angel is on the receiving end after he has sex with fellow vampire Darla.
- In Just Shoot Me! Finch comes into work after sleeping with his supermodel girlfriend and somebody comments, "Wow, the only time I've seen you this happy is two years ago whe—you had sex, didn't you?"
- In another episode, Nina claims that Maya has sex every twelve months, which is how she knows to set the clocks back for Daylight Savings Time.
- In French series Lazy Company, Louise can tell almost instantly that formerly shy virgin Private Henry is not a virgin any more, because he is "a little taller, a little less honest".
Dr. Cox: Hey, Newbie, what's up?J.D.: Everything! Everything's up!Dr. Kelso: Rise and shine, sport!J.D.'s narration: What, did someone send out a flier?!Todd: Hey, J.D.! How's your penis?J.D.'s narration: All right, calm down, he says that to everyone.
- There's only one day of the year when Dr. Bob Kelso's in a good mood (the day after his wedding anniversary) so people only ask him for anything once a year. This actually turns out to be a subversion: his wife always spends the anniversary at "fat camp". Kelso, however, allows the myth to continue so people only ask him for things once a year.
- Another subversion where JD has trouble getting it up and walks into work thinking everyone is doing this when they're not:
- Another example is Turk, who demonstrates an uncanny ability to always know when two people have had sex. He deduces J.D. and Elliot's hook-up solely on how they exchanged nods at work. He then points out two male orderlies who he claims have started dating, and he's quickly proven right. In J.D.'s case, explained by the sex gongs they bought each other. Except, of course, when JD moves out and Turk still hears it...
Turk: "Yeah, buddy!"
- A great example is when Dr Cox starts dating pharmaceutical rep Julie (played by Heather Locklear) in season two. He goes from surly Cox to carrying Julie piggyback singing "Perry's gonna get some loving!" while she smacks his ass. He even winks at J.D.
- Turk learns about Denise's and Drew's relationship from Todd, who's apparent super-pervert skills allow him to detect any sex in the hospital, their position, and what clothes they are/aren't wearing.
- "Why won't you let him take off his pants?"
- In Frasier the incredibly uptight Niles was oddly chipper — when someone called him on this, he responded with I Have Just One Thing to Say: "I find that comment boorish and offensive and... impossible to deny!"
- Parodied in another episode, when Roz and Frasier end up sleeping together after a night at his apartment. The next morning, as a panicked Frasier tries to cover up what happened, Martin enters:
Martin: Mornin', Fras.Frasier: Morning, Dad.Martin: You see the paper yet?Frasier: Uh, no, I haven't.Martin: Big story about how Roz's purse spent the night on the coffee table.
- Parodied in another episode, when Roz and Frasier end up sleeping together after a night at his apartment. The next morning, as a panicked Frasier tries to cover up what happened, Martin enters:
- In season three of Glee after Will Schuester and Emma Pillsbury finally have sex (after the New Directions finally win at Nationals) Sue sees her the next day and quips "Why do you look different?"
- Friends: In "The One With Phoebe's Husband", Ross was dancing down the street and was called out on it by an old lady: "Well, somebody got some last night". He gleefully shouts back "twice!"
- In the pilot, Monica has just been with Paul the Wine Guy, and her co-worker calls her on why she's smiling all the time. As Rachel said earlier, "It looks like you slept with a hanger in your mouth!"
- In "The One After Ross Says Rachel" when Phoebe sees Chandler and Monica for the first time since their trip to London, where the two hooked up, she immediately yells out "You had sex!" to which the two start sputtering and trying to deny it. Phoebe says to Chandler, "Well, obviously not YOU. I meant Monica." Monica then denies it as well. In a rare subversion, Phoebe accepts this, saying "Man, this pregnancy's throwing me all off."
- An episode of Will & Grace had two characters do this to Grace, with one actually able to identify the other man with this too. Both cases are a simple "You had sex!"
- Karen takes this Up to Eleven. She's able to tell exactly what Grace has done with a man in a matter of seconds. Grace is understandably terrified of this power.
- In That '70s Show, the day after Eric and Donna have first made love, a weirded-out Donna appears from Jackie's point of view to have the words "I had sex" on her forehead. Eric, on the other hand, had the words "Guilty" written on his forehead when talking to Donna's father.
- In Night Court, the day after Christine gets charmed by a young artist she successfully defended, she shows up smiling as usual. Resident lecher Dan takes one look at her and declares "You bopped the kid!".
- In Who's the Boss?, Tony runs into Mona after he's had a "successful" date. Mona nonchalantly busts him.
Tony: [stunned] How could you tell?
- She also knows he didn't sleep with Angela, because she wasn't singing "Climb Every Mountain".
- "Endgame" has Tony doing this when McGee walks into the office extremely happy. Tony refers to it as "Pulling a Heston" in a reference to Planet of the Apes.
- Ziva does it to Tony once as well — gleefully. "It's okay to admit it, we're all adults here!" Of course, Fornell is behind her: "That's a subject I'd be willing to debate, Officer David."
- Life: Crews got the picture when he and Reese are on their way to the desert, and a song's playing on the radio, and Reese is humming along without realizing. Crews quips, "You were humming," Reese goes, "What? No I wasn't," and Crews goes, "When people hum without realizing, it usually means they're... happy." To which Reese replies, "I wasn't humming, and I'm not happy!"
- What really blows her cover is when their boss calls the hotel room the two are staying in, and immediately starts talking dirty over the phone having assumed they had separate rooms and that Reese would answer.
- Rather a sad example in Gilmore Girls. Lorelai comes home and sees Rory and the very married Dean stumble out of Rory's bedroom looking dishevelled and a little too happy. The anger and disppointment on Lorelai's face is heartbreaking.
- In season two of House the team has gathered in the middle of the night and wonder what is taking House so long. They know he left with Stacey, but Cameron is sure that they didn't have sex (while Foreman hopes they did, since it might put House in a better mood). Enter House, singing and smiling. Played with, as House was not happy about the sex itself (he hires prostitutes from time to time, so...), but because he still had feelings for Stacy.
- Spin City
- On Cheers, Woody Boyd and his fiancée lost their patience (and most likely their respective virginities) just one night before the wedding. Sam was the first to figure out why, of course.
"You're smiling the way I smile after I..."
- One episode of Stargate SG-1 features Carter and O'Neil riding an elevator with Carter humming the whole way, prompting an amusing exchange.
- It gets better: Word Of God says she was supposed to hum the MacGyver theme tune to surprise Richard Dean Anderson, but no one could remember it, and asking him would've spoiled the surprise.
- Then there's a scene in the episode "Crossroads" involving Teal'c, of all people. An old flame has come to the SGC to get help. They are shown kissing in her room. Cut to Teal'c leaving the room grinning from ear to ear as Daniel walks up.
- One episode of 7th Heaven features Annie and Lucy sharing knowing glances over (I think) ice cream after they'd both gotten some.
- In season two of Veronica Mars, immediately after Veronica sleeps with Duncan she bumps into Logan who says she looks different and asks if she's changed her hair. At home her father makes a similar comment and she wonders whether he's really such a good detective that he can tell she's had sex.
- Averted in Degrassi: The Next Generation: J.T. keeps bragging about his and Liberty's sex life, but Toby doesn't want to hear anything else about it. Then Liberty dumps pop all over J.T.
- Happens to C.C. and Niles in The Nanny. Niles enters singing and C.C., normally an Enemy to All Living Things, gets a scene where she sings and attracts a dove to her hand like a Disney princess.
- In another episode, Fran drunkenly stumbles into Max's room and ends up sleeping in his bed. The next morning, they panic and wonder if they had sex, but ultimately decide it didn't happen, as they each have a particular "tell." But then, just as the episode ends, they begin doing those very things.
- Played Straight in Bones, Season 2, Episode 14 'The Man in the Mansion.' Bones comes into work looking 'very happy,' and Angela instantly knows she's had sex with Sulley.
- Chief Johnson in The Closer gets very cheerful when she gets some.
- Though he really tries to hide it, Beckett can tell every time Castle has slept with Ellie Munroe.
- In the second episode of season five, Lanie can immediately tell that something is different about Beckett on her first day back to work, and eventually works out that it's because she's having regular sex. This causes Beckett a certain amount of fluster because she's trying to keep the fact that she and Castle have started a relationship secret from everyone.
- Happens offscreen on Party of Five. Nina was immediately able to tell that Julia was no longer a virgin.
- Community played with this trope in the episode Modern Warfare. Jeff and Britta have sex on their study group's table during a paintball tournament, and as they both walk to their study group the next day, they remind eachother "nothing's changed". Abed instantaneously picks up on the dynamic changed and makes note of it. No one notices.
- Ron Swanson from Parks and Recreation always dresses like Tiger Woods after a night of sexytimes.
- Subverted in Sliders where it is actually Wade's disheveled and decidedly un-chipper appearance and demeanor that cause Quinn to say "Did you get lucky or run over?" Neither; she'd been partying with vampires who were trying to change her.
- Barney does this in How I Met Your Mother. "Aww, man, you guys did it, didn't you?"
- After spending the whole film/web-series longing after Dr. Kelly in Battlestar Galactica: Blood & Chrome, Adama finally gets to do her after talking about her dead husband and how the war-machine lied about this death in order to boost enrollments. Shortly after he finds Coker playing on a piano and takes a swing of expensive wine with a wide smile on his face.
Coker: Just had to frak her, didn't you?
- In Taxi, after Latka got married to Simka, he ended up stranded in a broken down cab with a female cabbie in the freezing cold. She told him the only option was for them to have sex or freeze to death. After the ordeal, Latka went home hoping Simka wouldn't find out, but as soon as they hugged, Simka screamed, "YOU DID IT WITH ANOTHER WOMAN!"
- New Tricks: The boys have this reaction when Sasha enters the office with a spring in her step in "The Lottery Curse". Leads to a Side Bet about whether she had or not.
- Farscape: Chianna and Rhygel are forced to share a one-person "shelter tube" while the ship's atmosphere is vacuumed out, provoking the following exchange:
"I don't care what you call it, stop sticking it in me!"(Farting noise)"What was that?" (her a voice is several octaves higher than usual)"What did you just do?""I'm sorry, but I always fart helium when I...I mean, when I...""You're DISGUSTING!"
- Knights of the Old Republic II: Given that the result of getting enough light side points is a sort of healthy glow, Mira invokes this by commenting that she thought the player and whichever potential love interest he/she has a higher Influence with "hooked up a power coupling".
- Dragon Age II: All of the post romance banters but this one is particularly good.
Merrill: Are you happy?Anders: Beg your pardon?Merrill: S/he seems happy. Hawke, I mean. Are you?Anders: Yes. I suppose I am.Merrill: Good. You've spent much too much time being grumpy. It's a nice change.
- Hinted in Dragon Age: Inquisition by a pair of Orlesian courtiers hanging around in the main hall at Skyhold. After the Inquisitor and their romance partner of choice have cemented the pairing, these two can be overheard gossiping about things. Their exact commentary depends on who the Love Interest is.
- Outright stated if a male Inquisitor romances Dorian and has him and Cole in the party later. Cole remarks on how good it is to see Dorian smiling because of the Inquisitor.
- Faye's commentary in Questionable Content when watching Marten going home after being away longer than anticipated: "He is skipping. A bluebird just landed on his shoulder! Random pedestrians are joining him in a complicated dance routine!"
- Attempted again by Dale, though this time Faye is just annoyed at it.
- The Web Comic Wapsi Square does this here and here with (another) Monica.
- Policeguy does indeed break into song and dance with animals and rainbows.
- Hipbone gets one later on, resulting in surprisingly long-lasting benevolence. Eventually it wears off.
- Makes an appearance in this Least I Could Do strip.
- Subverted in a later strip where nobody can identify Rayne's "I just had sex with a midget hooker" face (though in their defense, said face looks like he's having a stroke or something).
- Several times in Dominic Deegan. Most notably, when Greg and Pam do it for the first time, Dominic figures it out because, as he points out, some people have a "glow" about them after their first time, but because Greg is a powerful White Mage, in his case, it's a little more literal.
- Narbonic: Mell and Artie come back from a mission to find Helen and Dave very disheveled and the lab a mess. When Artie asks about the mess, they claim a "series of lab accidents"; Mell just says "I can't believe you guys finally goinked."
- When Mell explains to Artie: "I mean, check him out, he's wearing the red shirt ... ." "The shirt is significant" "It's his best shirt, and it's always Thursday in the rotation. He moved it up to Monday. Plus he cleaned his glasses." "From this you deduced he's had sex?" "No, I knew he had sex 'cause he's smiling. I'm just trying to educate you"
- Twice with Hazel in Girls with Slingshots. The first time, she didn't actually get laid, but it's the same general reaction. The second time...
Jameson: Oh, thank god, you're finally getting laid!
- Out There: The insightful Miriam concludes that Sherry has broken her long dry spell upon observing the latter's visible discomfort with discussing the topic ; James makes a lucky guess based on a similar observation , and Clayton explains the most compelling reason she's unable to conceal what everybody else can see .
- Dan and Mab's Furry Adventures: Alexsi is very happy after her date with Pyroduck. This trope is all but confirmed here.
- Sabrina Online: Zig Zag always seems to know when Sabrina's been with her boyfriend. In Zig Zag's case it's not "Did you just have sex," but "You got laid! Good for you!"
- In Rhapsodies Kate's employees have noticed this... frequently... and it's getting on their nerves.
- In Gunnerkrigg Court, Parley and Smitty teleport in, blushing - Renard sniffs them and chuckles, to their chagrin.
- Magnificently set up in Ménage à 3 in this strip. The actual dialogue appears, in variant form, in the next strip, but the facial expressions in that last panel there say it all.
- Mordred says it (although not in so many words) in this Arthur, King of Time and Space strip.
- Joe says this to Danny in this Dumbing of Age strip, after the latter strolls into their dorm room practically singing. He's not that far off.
- S.S.D.D: It doesn't take much for Corporal Gray to figure out that not only Julian and Tessa (whom he's been subtly trying to set up) got laid last night, but also everyone else on the squad.
- In Judecca, the Hooker with a Heart of Gold Snow can see a morning-after glow from a mile away, to Nayko's infinite dismay:
- In 'Let's Drown Out WWF No Mercy', Gabriel Mortom has created a wrestler to imitate his friend and commentary partner, Ben 'Yahtzee' Croshaw, and have stated that everything about Wrestler!Yahtzee, sans the face, is accurate to the real one including a rather pompous entrance dance. According to him, Yahtzee does the exact same dance after he got laid.
- In Avatar: The Last Airbender, Azula makes an offhand comment about how Mai has been in a "strangely good mood lately." It is subtly implied that she has been sleeping with Zuko.
- Time Squad In "Ex Marks the Spot," Larry suddenly acts cheerful and more accommodating around Tuddrussel. Otto even questions why Larry is so cheerful. The sudden change in mood was handwaved as Larry finally giving up being snarky and being nicer, but given the suggestive imagery in Larry preparing Tuddrussell's meal (i.e., the gravy being pumped inside a turkey to the point of near bursting and a lone cherry sinking into the turkey), it had to be something more.
- In Family Guy Brian is able to instantly tell when Stewie had walked in on Peter and Lois having sex.
- In King of the Hill, Peggy remarks that Dale and Nancy's relationship is so passionless that they only have sex once a year, on Dale's birthday. However, in that particular episode the pair rediscovers their passion, and the next time Peggy sees Nancy she figures out that they did it — and panics. "Oh no, we forgot Dale's birthday!"