Casual Kink

"Buffy (about Riley's lunch selection): ... A Twinkie! That's his lunch? Oh, he is so gonna be punished.

Willow (pouting about currently being single): Everyone's getting spanked but me."

- Buffy the Vampire Slayer, "The I In Team"

Sometimes sexualities such as sadomasochism and fetishism come into play simply as a kinky counterpart of Bi the Way: The character just happens to be into BDSM (or similar). That is, any variant of Bondage (as in tying each other up with ropes or handcuffs), Dominance-games, and/or Sado-Masochism (as in spanking and such). The origin of the name is a merging of the old terms Bondage & Discipline, Dominance & Submission, and Sadism & Masochism. No big deal is made out of it, at least not by the main characters. This can be a good excuse to play with gender roles and power dynamics, an excuse to get the Heteronormative Crusaders all riled up, or simply a way to put a character in an unexpected situation or let a conversation take an unexpected turn.

While usually about individual characters, this trope can also be a characteristic of a Free Love Future or similar world. In these cases, the fact that kinky sexuality is so normal that no one thinks twice about it in this world is often used as a way of pointing out how different that world is from our own.

People playing with Casual Kink do it Safe Sane and Consensual, and are likely to have a Safe Word. People who see a little bit of what they are doing, without getting the whole picture, might sometimes make the classic Abuse Mistake.

Casual Kink is one way to portray (or show interest in) a Fetish.

Compare and contrast the tropes where kinkiness is used to indicate that a character is cool or a bad person.

Anime and Manga

 * Pokémon: Trip's Servine apparently doesn't mind Ash's Snivy whipping him until it collapsed. Granted, Servine was under the effects of Attract, but other Pokemon usually snap out of the effects after an attack.
 * It's now a Me Me to call Trip's Servine a masochist.
 * In the Diamond and Pearl seasons of the same show, Gardenia was strangely fond of taking the brunt of various Grass-type Pokemon's attacks.
 * Ruby from Rosario Plus Vampire seems to enjoy being the submissive person between her and Tsukune, the latter of whom doesn't really have an interest. Ruby not only enjoys pain, but reminds Tsukune repeatedly that she does in often double entendre.
 * Nabari no Ou: Gau's masochistic tendencies are played for laughs in an omake strip, and Raikou is later implied to be a sadist during the Alya Arc.

Comic Books

 * Dilbert once chatted with a woman calling herself Mistress Cruella. Afterward he looked quite startled. What she said to him was, of course, left to the reader's imagination.
 * Pondus has a lot of this. Often used as a tool to create awkward situations (Jocke and Camilla walking in on Jocke's mother and stepfather doing a scene), but sometimes just for cuteness (Pondus wife bringing home her nurse uniform from the hospital in return for him taping her favorite Soap Opera).
 * In the first album of Lucifer, Casual Kink and Bondage Is Bad are both expressed as attitudes held by characters: Jill hold a little speach about how she's not into BDSM herself but doesn't mind it as long as it's consensual - while Elaine write a story within the story where her way of establishing the bad guy as bad is to state that he fantasizes about three creepy things, one of them being tied up women. (The other two are money and selling drugs. It should be noted that since this is in the first issue, Elaine is still an immature 12-years-old inexperienced psychic.)
 * When Deadpool finds his business unexpectedly booming, he hires an assistant to keep his schedule straight. She also helps design several new costumes for him. When she shows the sketches, Deadpool asks why some of the costumes have high heels. She responds "I'm kinky".

Fanfic

 * There are a number of very popular and widely read All Human BDSM Twilight fanfics including Master of the Universe by Snowqueens Icedragon, which has over 56000 reviews (!) on fanfiction.net alone (The full uncensored version on twilighted.net has over 23000 reviews.) The Dom Edward/Sub Bella seems to be a genre in itself of Twilight fic - there are numerous examples, but this is the most popular.
 * Several Neon Genesis Evangelion fics support the idea that in the (unlikely) event where Asuka and Shinji pair up, they will inevitably involve themselves into BDSM with Asuka as the slave and Shinji as the master. Completely foregoing the fact that Asuka would never, EVER, do such a thing.
 * Power Plays takes it one step further: Hikari, sweet and innocent Hikari is into BDSM as well, with the same arrangement. Both pairs go at it 24/7 and neither use safe words... And then we haven't even mentioned that Misato practically forced Shinji to be Asuka's master by watching their relationship and every time it looked like things are going steady, Misato dropped a not-so-innocent remark to trick Shinji into thinking Asuka is only playing with him. Her excuse when Asuka ratted her out was that she wanted them to take their relationship seriously, ie. they shouldn't even start it if they're going to break up later (she was speaking from experience but that's still no excuse for forcing two fourteen year-olds into BDSM).
 * In some of I Carly's more lemony fics, Sam and Freddie take their Belligerent Sexual Tension friendship and exaggerate it to having Freddie be a sadomasochist to explain why he's fallen in love with a girl who repeatedly and constantly abuses and degrades him.

Film
"Sara McDowel: Listen, if I say that sort of thing again, tie me up and gag me.
 * LA Story.

Roland Mackey: [her ex-husband] We tried that once, but you started laughing."


 * Exit to Eden takes place on an island where BDSM and Fetishism is the everyday norm. And it's hardly even a real part of the story, more like a exotic background for an ordinary detective story.
 * In Preaching to The Perverted, the main character is sent by a Heteronormative Crusader to infiltrate a BDSM club. As he gets to know the people there, he finds out that they are just ordinary people with an unusual sexuality, not any better or worse than anyone else.
 * While most of Secretary averts this trope quite hard, it does pop up twice. In the middle of the movie, Lee is listening to a tape about coming out as a dominant or submissive, assuring the listener that BDSM is a capacity for a wider range of experience. More importantly,
 * There is a quick instance in the movie Forgetting Sarah Marshall where the main character, in an attempt to forget his ex-girlfriend starts having sex with lots of different women, one of whom is a fairly quiet girl who wouldn't stop saying "hi" to him. He asks if she could stop because it was getting a bit weird. Without missing a beat, she tells him, "You can gag me." As he's left surprised, she explains that she brought a gag with her and some handcuffs too, then asks, "Do you want to gag me?" He finally replies, "Actually, I kind of want to now."

Literature
"‘Fitz,’ Anji hissed. ‘Are you telling me you really don’t mind trotting around starkers in a collar and lead?’
 * The Slave World novels sometimes casually mention BDSM play done in Britain's timeline. In the Alternate Timeline, where the Roman empire never really fell and the story takes place in a England that was never an Empire, much of the everyday social life is kinky Fetish Fuel - not only to many readers, but also to visitors from the first timeline.
 * The Dresden Files plays this straight several times with Molly Carpenter. Her kinks are referenced several times in the series and are usually just as quickly forgotten. Possibly justified in that the books are supposed to be Harry's case files, and he considers these to be Too Much Information.
 * Perhaps surprisingly for a guy who started traveling with the Doctor a few years before the Summer of Love, the Eighth Doctor Adventures' Fitz Kreiner doesn't stop at casually coming out to the reader, he also makes what seems like a semi-sincere crack implying this trope:

He grinned. ‘Are you kidding?’"

Live Action TV

 * In the Masters of Horror episode Homecoming, the phone rings while the main characters are having a BDSM session. He answers the phone, but she keep whipping him a bit just to embarrass him in front of ther important political figure he's talking with.
 * Buffy the Vampire Slayer has several mentions, including the Page Quote. The same episode featured some dialogue by Anya that strongly implied that she and Xander were practising (mild) BDSM. Nobody ever seemed to mind the idea itself, just the fact that she was talking about her sex life with other people at all was treated as awkward. But on the other hand, the Riley/Faith sex scene in "Who Are You?", and the dialogue around it, strongly implies that BDSM, or any sexual role play, is a way for emotional cripples to evade true intimacy. Joyce and Giles played with handcuffs in "Band Candy" (far Too Much Information for Buffy). Willow mentioned wanting to be spanked on "The I in Team", and Anya in the same episode saying, "Yes, we've enjoyed spanking." Buffy mentioned "a favor" with outfits to Riley in "Family", and Faith said that safe words were for wusses on "Consequences" (technically the last one is not BDSM, since it's not safe, sane or consensual).
 * Averted with the Buffy/Spike relationship which involves rough sex, handcuffs, biting (by Buffy, not Spike) and Making Love in All The Wrong Places, yet despite the fact that Buffy participates fully she always feels ashamed and tries to hide what they're doing from the other Scoobies.
 * Blair and Chuck's relationship on Gossip Girl involved handcuffs, frequent references to punishment, roleplaying, and the other uses bidding paddles can be put to.
 * Phoebe and Mike in Friends are hinted to be into it; indeed, at one point, Phoebe finds a pair of fluffy handcuffs and complains "these would never be able to cuff a man to a water pipe - they're much too flimsy."
 * Chandler also once dated a dominatrix, who left him handcuffed to a chair because she had to go to a meeting, with hilarity ensuing.
 * In Desperate Housewives, where Rex was the only really sympathetic character in the whole show (which is probably why they killed him off), and his conservative wife's reaction to his kink was portrayed negatively.
 * It's not strictly that. She was willing to go along with it because she loved him, but when she thought he'd bragged she reacted negatively.
 * Implied in a Getting Crap Past the Radar kind of way with Brigadier Bambera and Sir Ancelyn in the Doctor Who story "Battlefield". Unless you think there's some other interpretation to be put on him asking if she's single the day after their first meeting involved her beating him up and manacling him.
 * The Charmed episode "The Wendigo" reveals that Phoebe just happens to have a pair of handcuffs lying around... and refuses to admit where she got them.
 * NCIS. Perky Goth Abby makes frequent casual references to handcuffs, straitjackets, sleeping in coffins, etc, even when talking to apparently straight-laced nerd McGee, making you wonder about just how kinky their relationship got.
 * Ziva frequently implies she's interested in bondage.
 * In House, Chase is into bondage, and while he's occasionally ribbed about it, no one thinks he's a weirdo for it.
 * But still spoiled in an episode where the husband has an attack while going into rough stuff with his wife. It turns out his wife, for no reason that is stated clearly, has been poisoning him with a gold-based compound.
 * In CSI with the character of Lady Heather, a highly intelligent, articulate, and urbane dominatrix who was briefly one of Grissom's love interests. For the most part, she was portrayed as a generally good, decent person.
 * But then CSI spoils it by having every other victim or criminal of the week be into rough sex.
 * Female protagonist Beckett in Castle is shown to be interested in BDSM, immediately identifying a specially-made pair of handcuffs and the shop which it probably came from. Castle's safe word is "apples".
 * In Sugar Rush, the main character tried spanking, which was portrayed as normal, though the person who suggested it turned out to be unfaithful.
 * In Coupling Jeff and his girl-friend are shown to engage in bondage in one episode where it is played for Hilarity Ensues rather than for moral disapproval.
 * A really jaw-dropping example in the Star Trek Deep Space Nine episode "Let He Who Is Without Sin...", in which it's casually dropped that Worf's and Jadzia's (happy, consensual) sexplay has been known to lead to broken ribs. Some way past Safe Sane and Consensual if you're human, although knowing Klingons... (Indeed, Klingons see a broken collarbone on their wedding night as a blessing on the union.) Not to mention how easily broken ribs can be repaired in the series.
 * Jade from Victorious just happens to enjoy pain and likes seeing her boyfriend getting smacked around by Cat, and isn't afraid to offhandedly mention that.
 * Fiona on Burn Notice has been known to invoke this, mainly to mess with Michael's head. In one instance, she picked up a pair of handcuffs (intended for use in one of Michael's plans) and asked him, "Where have you been keeping these?" Poor Mike nearly lost his grip on his power drill.

Video Games

 * In World of Warcraft, your goblin female character sometimes say: "I'm a free spirit. I don't like to be tied down. Wait, you meant literally? Oh, I'm totally into that!". Characters of certain other race-gender combos also say things that can be interpreted in a similar direction, but they are less obvious about it.

Web Animation

 * Salad Fingers is big on this - the main character himself is a rust fetishist, looking for rusty spoons to caress. As surreal as these stories are, his fetishism serves to make him seem less alien and inhuman.

Web Comics

 * Collar 6 is set in an Alternate History where BDSM became commonplace and it's perfectly acceptable, for example, to walk in a public park in latex with your collared personal slave on a leash.

Web Original

 * The Nostalgia Critic has no problem admitting he'd be happy for the Chicago women to kill him, as long as they were playing The Cellblock Tango.
 * One of the healers in Guts and Sass: An Anti-Epic, Litin, is an empowered, self-confident masochist. He likes to get beat up, in and out of sex, and no one makes a big deal about it.
 * One of the few things Spoony likes about Final Fantasy VIII is Quistis, who he finds attractive. When Squall seems to ignore her, Spoony exclaims "She's 18 years old and whips people! I have to go to Tijuana and pay for women like that to pay attention to me!"

Western Animation
"Dan: "Ahh, so clean you could eat off me." (meaningful look)
 * Family Guy -- Peter might not be very "good" or "heroic" most of the time, but the sex he has with Lois is almost always presented as a mutually loving and kinky relationship; they're even seen discussing their day-to-day lives moments before they suit up and Lois cheerfully informs Peter that "the Safe Word is banana".
 * Callie of Ugly Americans...but what did you expect from the literal spawn of Satan?
 * The eponymous character of Dan Vs hints rather un-subtly in one episode that he'd like his friend Chris to eat off of him. This is passed off as nothing and dropped for the remainder of the episode.

Chris: "I'm not going to do that."

Dan: "I'm just saying you could..!"

Chris: "Well, I'm not going to."

Dan: FINE! (slams fist and pouts)"