Can't Have Sex Ever

"Let me explain the lore here, okay? They suffer, they fight. That's business as usual. They get groiny with each other, the world as we know it falls apart."

- Cordelia from Angel, about Buffy and Angel's relationship.

"So you have to decide between a life without sex, or a gruesome death? Tough call."

- Phillip J. Fry, Futurama

Alice and Bob are in love. However, thanks to a Curse, Curse Escape Clause, Applied Phlebotinum, Clingy Costume, or some other kind of mystical reason, or practical reason, the two of them Can't Have Sex Ever. Often this tends to forbid sex between the cursed character and ONLY the one they love -- they could probably boink anyone they don't care about -- though it's not uncommon (particularly in the case of the more practical versions) for the cursed character to not be able to have sex with anyone without something bad happening. This is not No Sex Allowed, which is an example of nobody at all being allowed to get down and dirty. Bob and Alice may or may not still try to see each other, sex be damned, but as a general rule this leads to the end of the relationship. This is a guaranteed source of Unresolved Sexual Tension that can never end, not to mention Celibate Hero.

Some couples will try to break the curse, find a cure for the disease or try to otherwise circumvent whatever is keeping them from consummating the relationship, but due to Rule of Drama, Finagle's Law and Status Quo Is God, Failure Is the Only Option in many such cases.

This happens a lot to Horny Devils. See also Nature Adores a Virgin and Courtly Love. Often leads to But I Would Really Enjoy It.

Contrast with Asexuality, which is more like Don't Want Sex, Ever.

Anime & Manga

 * Chobits uses this as a source of drama: penetrative intercourse with Chii will activate her reset mechanism and erase all her memories, destroying her feelings of love in the process.
 * The manga version, anyway. In the anime, it's more vague, but apparently "only the one who is just for me can ever come inside."
 * As pointed out in this strip, other options are not mentioned
 * ... at least not on-panel. Considering how much of a horndog Hideki really is, it's only reasonable to assume that the though already crossed his mind, and will most likely explore them with Chii off-panel
 * Being fair to Hideki, though, it's a good sign of how he's grown over the series, as it means he's not so bothered by his virginity anymore, and that he's mature enough to know that sex isn't worth losing his relationship with Chi.
 * Alice 19th: Not sex, but close. Mayura, jealous over Alice and Kyo's relationship, curses Kyo so that if he ever hears a word of love from Alice he will die.
 * My Balls: The premise is that a guy had a superpowerful demon sealed in his right testicle, so he has to avoid having sex or ejaculating in any way for a month, or she will be released and destroy the world. This is the cue for every hottie in Hell to come banging on his door.
 * In Yuria 100 Shiki, Yuria is a Sex Bot programmed to become the unquestioning love-slave of the first person to insert the proper hardware, something she'd prefer not to happen. The alternative is no sex at all. She's a Sex Bot programmed to have sex...
 * Vaguely used in Black Bird.
 * Fruits Basket: Many members of the Sohma family transform into animals from the Chinese Zodiac if they come into contact with someone of the opposite sex, though the series is never more specific than 'hugging'.
 * Shigure mentions this in the explanation to Tohru, saying that since hugs cause the transformations, sex is very awkward. It's also worth noting that as Kagura demonstrates, other Zodiac members don't cause a transformation.
 * Turns out Shigure actually has personal experience in the matter.
 * At one point, Black Haru comments to Tohru that it's possible to do it without actually embracing, though Yuki and Kyo quickly shut him up before he can go into any specific details.
 * Over the course of the series, it's gathered that it is very specifically embracing or hugging another person. Kissing is fine (we see that) and so assumedly sex is fine as long as there's no... uh... lets just leave it at that.
 * Played straight in Mai-Otome, thanks to the limitations of their Applied Phlebotinum. Akane and Kazuya come this close to averting the trope after eloping, but they keep being interrupted at inconvenient moments, culminating in him getting dragged back to his home country and her getting arrested. Finally, someone arranges a way for them to stay together, but then flat out tells them that this trope still applies.
 * Okusama wa Joshikosei plays this one for laughs. The male lead legally marries his student but her father forbids the act with a written contract until she graduates.
 * Oku-sama wa Mahou Shoujo (don't confuse it with the former) features a character who would lose her powers when she kisses. This may be a case of G-Rated Sex, though the series never says that sex would do it.
 * Ninja Scroll's Kagero, a female ninja, is so permeated with poison, that her very touch is deadly. A demon by the name of Tessai finds his stone body fatally weakened after attempting to rape her.
 * Basilisk's Kagero is similar (Basilisk being based on the novel The Kouga Ninja Scrolls, which is among the works Ninja Scroll drew inspiration from).
 * In Bizenghast, Edrear has an irremovable exoskeleton, which means he can't have sex. Word of God is that it is supposed to deter slash fiction between Dinah and Edrear (didn't work), but he does shed every three months.
 * M. Alice LeGrow is adorably naïve if she expected such a ploy to actually work.
 * While they couldn't mention anything explicit given the age of their target audience, Cyborg Guy's relationship with his girlfriend is visibly strained by the fact that the only flesh and blood part left of him is his head.
 * While they couldn't mention anything explicit given the age of their target audience, Cyborg Guy's relationship with his girlfriend is visibly strained by the fact that the only flesh and blood part left of him is his head.

Comics
""Oh, you cannot imagine how annoyed he is.""
 * The Sandman: Dream and Nada.
 * Legion of Super-Heroes: Wildfire doesn't actually have a body, having been turned into an Energy Being by a Freak Lab Accident. This puts severe stress on his romance with fellow Legionnaire Dawnstar. Eventually he learns to create a solid body... but it's still made of energy, and Dawnstar gets burned trying to touch him. This is the point where he tells her to just go.
 * Superman, or at least certain interpretations of him. Check out the infamous Larry Niven essay "Man of Steel, Woman of Kleenex".
 * Brody expands upon this topic in Mallrats, to Stan Lee's amusement.
 * However, Superman is currently married to Lois in the comics; they share a bed and they've been shown after sex multiple times. The most likely explanation is that Superman has some control over the force of his ejaculation.
 * TV series Smallville actually addressed this issue. Clark and Lana only slept together when Clark was depowered or when Lana was empowered (temporarily). In a much later episode, Clark explains that his Kryptonian "training" from the AI reconstruction of his father included learning "control" when Chloe expressed concern regarding Clark's romantic involvement with her cousin.
 * Often fanonically Handwaved out by explaining his powers off as telekinesis.
 * This was very likely the reason he had to lose his powers to be with Lois in Superman II.
 * In some versions, like Lois and Clark, this trope isn't a problem at all; but even so, he and Lois are shown to be unable to have children because he is, technically, not human
 * X Men comics have many mutants have a mutation that makes sex impossible. Examples include Rogue and Wither, who respectively hurt or kill whatever living things they touch. Their partners would effectively need full body condoms.
 * Wither's case reeks of Idiot Ball as his power only affects organic matter and there are more than enough inorganic characters -- one of whom had a crush on him. Instead, he chose to pine for a wholly organic girl who was dating someone else. This didn't end well.
 * In Rogue's case, the problem wasn't insurmountable: there have always been characters immune to Rogue's absorption power (e. g. the Avengers' Wonder Man in her debut story) and also quite a few who could protect themselves through their own powers (e. g. Magneto in the Age of Apocalypse) or through a machine (e. g. the apparatus Joseph built as a Christmas present). Another way out was exposing Rogue to the powers of mutants (e. g. Leech) or machines (e. g. the one used in the "love grotto" story in UXM #350) or mystical devices (e. g. the Siege Perilous) that can strip mutants of their powers, at least temporarily. In any case, with some help from Professor X and Danger Rogue finally learned to control her absorption power and now can have sex if she wants.
 * The Thing has had several lovers since his transformation (The main ones being Alicia Masters and Debbie Green) and this has been addressed a few times. The (overall) interpretation is that he can't have sex because he lacks genitalia, and Stan Lee himself has said that he never really thought about how the Thing could have sex being a giant rock-covered dude and didn't really consider it important in the first place.
 * In The DCU, Heatstroke and Coldsnap are lovers who are members of the villain team the Masters of Disaster. Their motivation for committing crimes is to earn enough money to find a cure for their 'condition' that prevent them from touching.
 * Jackie Estacado had this problem ever since he turned 21 and acquired his powers (and takes his frustration out on mob goons using Darklings and actually dropping a rabid one down in a Mafia Boss's pants) until they went autopilot and humped an unconscious Sara Pezzini. Usually bearers of the Darkness are male and when a baby boy is born the current owner drops dead. Luckily for Jackie, Sara gave birth to a girl
 * There is a loophole, that Darkness bearers can create constructs for this purpose. However It Got Worse when it was revealed that
 * Played for laughs in The Awesome Slapstick, when protagonist Steve Harmon is thrilled that high school beauty Barb Halsey loves his alter-ego, Slapstick. His Black and Nerdy friend Mike then points out that his Slapstick form lacks the requisite equipment...
 * Done with Fin Fang Foom in Nextwave.


 * In the last issue of Crystar Crystal Warrior, with his dying breath, the evil wizard Zardeth punishes Moltar and Lavour for betraying him by restoring Moltar's humanity, but leaving Lavour still a woman made of living magma. And this just after Lavour had finally realized that she genuinely loved him. Fortunately, Lava Is Boiling Kool-Aid, so they don't have to avoid each other entirely, but they can never touch.
 * Seems to be the case with Princess Kavatah in Megalex, at least as of Volume 1. A noble general tries to touch her romantically, and he bursts into flame. She believes it to be a curse.

Film
"Ilia: I have sworn an oath of celibacy.
 * Irena Gallier and Oliver Yates from Cat People. Irena is a werecat, and she and her brother can only sleep with each other without transforming into deadly panthers. However, both of them give in to their urges during the course of the film.
 * Frank and Lonette from Cool World, because 'noids' and 'doodles' (humans and toons) can't have sex without disastrous consequences.
 * The 2008 Incredible Hulk movie had Bruce and Betty almost start, at which point his wrist-mounted pulse-reader starts beeping. Bruce stops Betty, explaining that he can't get excited or else he'll Hulk out; she responds, in a disappointed tone of voice, "Not even a little?"
 * And yet one never heard Bruce Banner say "You wouldn't like me when I'm horny."
 * In Star Trek the Motion Picture, Ilia and Decker Can't Have Sex Ever, because Ilia is a Deltan, and sex with a Deltan is so intense that humans just can't handle it.
 * In the novelization, it's claimed that Deltans form a permanent mild-meld with their partners, so Decker and Ilia would wind up as a two-person Hive Mind. Most humans find this idea terrifying. Moreover, Deltans constantly produce pheromones that make everyone want to sleep with them even if they know better. So Deltans serving in Starfleet have to take an oath of celibacy.
 * MAD Magazine's take on it:

Kirk: With that chrome-dome of yours, I don't think it's necessary!"


 * In Bent, the main characters are a gay couple in a concentration camp. They are incapable of touching each other, standing within a foot of each other, or even looking at each other. What they can do, however is have incredibly emotional and vivid verbal sex.

Literature
": How could I argue with you, when you could kill me just by spitting in my face?"
 * Partial trope in The One Who Waited, Alice and the Boogeyman can technically never have sex, except
 * Debatable: Either the It is left to the interpretation of the reader.
 * In Piers Anthony's Apprentice Adept series. Stile's wife has been prophesied to have one child by her second husband. So as long as they don't consummate their marriage, Stile remains safe from death.
 * Cal Leandros is so afraid of impregnating the human he loves (he doesn't trust birth control at all) with his half-evil-fairy sperm that he will only boink other species that he's biologically incompatible with.
 * Thomas in The Dresden Files books can no longer even touch his beloved Justine - or even a scarf she made by hand - without being burned, because they truly love each other, and true love is holy water to White Court vampires like him. He's free to do anything he wants with anyone he doesn't care about and in fact drains the life force his demonic side needs through acts of lust.
 * It's even more difficult for Justine, whose protection against the White Court lasts only if her last sexual encounter was with her true love, i.e. Thomas. She loses protection if she gets with anyone else.
 * Georgina Kincaid of the Succubus books is a Horny Devil who can't date anyone she likes without sucking his life force.
 * This is a frequent problem in Anne McCaffrey's "The Ship Who..." series, where the protagonists are very handicapped humans who operate as the "brain" of a ship. They can't get physical when they are an immobilized body in a column. Averted halfway through the series, when one brain deals with the problem by commissioning a remote-controlled full-sensory human body, opening up the same possibility for other brains.
 * Also mentioned in the books is that one of the reasons the administrators will reassign brain-brawn pairs if they click too well is that there have been a few cases where a brawn has decided enough is enough and to crack the column to get at the chewy center inside (for this very reason, brawns are absolutely not supposed to have the access codes to the column, but sometimes obsession finds a way).
 * Confessors from the Sword of Truth can have sex, just not with anyone they actually like, because they accidentally release their power while love making, and it would essentially destroy their lover. This causes much drama for Richard and Kahlan in the first book. Once this is resolved, they have another problem because of some prophecy that she'll give birth to a male Confessor (who are Always Chaotic Evil).
 * Edward and Bella can't have sex in Twilight because he would crush her and/or suck her blood.
 * To be more exact, Edward refuses to have sex with Bella before marriage due to his old fashioned values.
 * Subverted in Spider Robinson's Callahans Crosstime Saloon series. Michael Finn, a humanoid alien cyborg, believes he can never have sex because (like Superman in the above example) his superhuman abilities would cause him to accidentally injure or kill whoever he has sex with. One of the other characters points out that he can still administer oral sex, and be given hand jobs.
 * Discworld wizards can't have sex because there is a risk that the resulting child could be a sourceror, a magician powerful enough to destroy the world by accident. They don't seem to have heard of non-procreative sex.
 * Judging by Moving Pictures, at least, the idea seems to be to never ever tell them anything about sex so that they have no idea how it works. If they don't know how to have sex, they won't, and no sourcerors will show up!
 * Good luck hiding that from the wizards raised in rural environments, especially Archchancellor Ridcully.
 * It's actually worse than not having discovered non-procreative sex; a sorcerer will only be born if they're the eighth son of an eight son. So in theory, there's lots of sex that can be had before they have to stop, and some wizard could never have a problem. This is mentioned in some of the early books, so there's a good chance it's the kind of canon that can be safely ignored.
 * Mostly, though, wizards don't have sex because they usually find magic more interesting. They're nerds, after all...
 * This is then possibly averted in Making Money, where it's revealed several necromancy students only want to be necromancers because they get the official skull ring which they claim is a 'babe magnet'. Technically it's only marriage that's forbidden. There's presumably only a problem if all eight children are with the same woman.
 * Ah, 'Postmortem Communications'.
 * In Unseen Academicals it is mentioned that Professor Macarona, at Unseen University on exchange, has apparently left a trail of angry husbands and at least one angry wife in other cities he's visited. Not his wife, you understand.
 * In the first book, Rincewind is describes as looking like an "apprentice enchanter who had run away from his master out of defiance, boredom, fear and a lingering taste for heterosexuality." Make of that what you will.
 * In The Light Fantastic Rincewind knows what orgasms are - he's had a few. Sometimes in company. His first use of real magic is compared to a good orgasm, and most wizards can use magic when they want.
 * Played on a villain in Exiles at the Well of Souls, when the sexually-perverse and licentious Antor Trelig is transformed into a Makiem, a frog-like alien race. Makiem don't copulate at all, they just release gametes into the water once a year without any physical contact. Karma's a bitch, eh?
 * In Isaac Asimov's novel The Gods Themselves, it is emphasized a few times that Earthborn and Moonborn people suffer from a slight sexual incompatibility due to Earth people's tendency to subconsciously move as in normal Earth-gravity during moments of abandon--an Earthman would be very likely to injure his partner in the lower gravity of the Moon.
 * The titular Catgirl of The Nine Lives of Chloe King technically can have sex, but her claws pop out when she's aroused, and they apparently have some sort of venom on them, so it's not recommendable for her partner. Apparently,
 * It's indicated to be a curse on the Mai. In the end of the books, the curse is broken. The TV series never made it that far.
 * Cal from Peeps has a sexually-transmitted parasite that gives most people who pick it up vampiric traits, something he didn't figure out until his ex-girlfriends went crazy.
 * The hitek, a near-future offshoot of humanity from Man After Man, are unlikely to survive having sex, as their bodies are so crippled by the accumulation of genetic defects that they need constant life-support to function. A hitek couple in the book require the approval of their physicians to even make the attempt,
 * In Louise Burton's Hidden Grotto novels (House of Dark Delights, Bound by Moonlight), there are two characters in love who may never touch - Elic, a dusios (type of sex-changing inccubus), and Lili, a succubus. They find ways around not having sex with each other...
 * The Narrator and Marianne Engel in The Gargoyle, mostly because
 * This trope heavily figures in The Sun Also Rises by Ernest Hemingway. Jake Barnes is very much in love with Brett Ashley. She even reciprocates! However certain practical (and metaphorically mental) issues preclude any consummation.
 * In the last book of the Emigrants tetralogy Karl Oskar and Kristina can no longer have sex since they have no reliable birth control and if Kristina gets pregnant again it will lead to her death.
 * Neal Shusterman's Scorpion Shards features an otherwise-Ordinary High School Student who is cursed to somehow suck the soul out of any girl he kisses. It also makes every girl he meets fall madly in love with him, but that's not much comfort.
 * In The Vampire Chronicles, once you're a vampire, you can't have actual sex. However, everything else practically becomes a substitute. Even the pattern on a carpet can bring rapturous pleasure to one's enhanced senses.
 * In a Polish vampire trilogy Nocarz, this can happen to a vampire couple if one of them gets neutralised . The victims not only lose their vampiric traits, but also react with deadly allergy to any physical contact with a normal vampire (it's implied this effect will pass with time). Knowing this, Vesper assigns his human friend to provide medical first aid to the neutralised vampires, as any other member of the team would kill them with barely a touch.


 * After gets neutralised, Vesper imagines her having a normal life,  . It's implied that it will work out in the future, unlike the rest of his hare-brained plan.
 * There's a cat character in Clare Bell's Clan Ground series who's like this. He's half Unnamed, and as most of the Unnamed are dumb, brutish, unintelligent cats, he fears passing on his Unnamed genes to any potential offspring. So, he leaves the clan during breeding time each year.
 * Every time Laurent and Thérèse try to have sex after they get married (or even try to sleep for that matter) in Therese Raquin, they are haunted by memories of Thérèse's first husband Camille.
 * From Warrior Cats: Medicine cats, although it's forbidden for Medicine cats to have mates and have kits some did anyway Like Yellowfang and Leafpool.
 * In Tales of Kolmar, Kantri have incredibly high internal temperatures. A human once helps one of the Kantri deliver a baby, has to reach in and turn it, and the flesh on the human's arms is so burned it comes off in rags. Humans and Kantri are not sexually compatible. The very idea that they could be is seen as absurd; there is a prophecy of human-Kantri children spelling the end of the world as we know it, but someone outright says that there might as well be a prophecy warning them to beware of a bull and a butterfly. So when the Lord of the Kantri falls in love with a human woman, they can't consummate..

Live-Action TV

 * Buffy the Vampire Slayer: Angel had one night with Buffy, which enabled his Curse Escape Clause and led to his infamous Face Heel Turn as Angelus. Angel has moved on to boink other women he doesn't love, but he can never close the deal again..
 * Played with on Angel with Cordelia and her beau, the Groosalugg. She has reason to believe that having sex will lead to her losing her precognitive powers; after spending time bemoaning, her response is to find a magical prophylactic so that won't happen.
 * Angel eventually has the characters work out that Angel's curse isn't the No Sex Allowed curse they originally thought but is, in fact, this trope played straight. In series 1, When Wesley and Cordelia discuss the idea of Angel and Rebecca Lowell having a relationship, Wesley points out the curse's requirement is "perfect happiness" and also points out how rare that criterum actually is. In series 2, Angel can get away with having sex with Darla, who he has complicated emotional ties to, because he experienced "perfect despair" with her. In series 5, Angel doesn't lose his soul by having sex with Eve because he doesn't trust her and they were under a mystical compulsion. Wesley reiterates that "perfect happiness" is very rare and most relationships are formed from "acceptable happiness" instead which is why Angel can have sex with Nina without his soul being endangered. As a result, the only people Angel Can't Have Sex Ever with are the women he regards as his true loves (and the ones he truly wanted to be with): Buffy and Cordelia.
 * Every pairing in Lexx suffered from this. Afflicted characters included a dead man who lacked certain parts, a severed robot head with no moving parts, and an alien who was "smooth round the bend". And that was before the plot device of the ship's coveted key -- a symbiotic energy life-form -- abandoning its host at the height of ecstasy...
 * And the writers loved to taunt the audience with it, too; when 790 gains a working arm, thus becoming a robot-head-with-arm, he tries to get his new hand in Xev's pants...but she's too tired from previous events to care and 790 loses the arm shortly thereafter. 790 would again come close to getting some actual action when Prince arranged for his head to be attached to the body of a moth breeder who had the key to the Lexx, as well as going through the United States military's service record to find the most well-endowed soldier to volunteer an equipment transplant to the moth breeder's body. Before 790 could get his freak on, his head was knocked off, leaving him bodiless again, and Xev went to "find" the moth breeder.
 * In an earlier episode, 790 attaches himself to a headless cyborg body found in a prison ship. However. reactivating the body causes 790 to be intermittently possessed by the personality of the body's previous owner, a Depraved Homosexual Scary Black Man rapist who immediately sets his sights on Stanley.
 * Dark Angel loved doing this to Max and Logan. At first they couldn't do it because Logan physically couldn't (he was paralyzed from the waist down). Then Logan gets better, but Max has been infected with a designer virus made especially to target Logan's DNA -- so any skin-to-skin contact with her would kill him. Then the show was canceled.
 * Pushing Daisies: Ned and Chuck. His power allowed him to bring her back to life at the cost of killing a bystander, but she will die if he even touches her, let alone if they attempt sex.
 * Although it's possible that the two of them are coming up with some workarounds: according to a throwaway line in a recent episode, there may or may not be "contraptions" involved.
 * Plastic wrap is a beautiful thing.
 * In season 2 of Torchwood, after, he finds that he can no longer have sex. This is the time that Toshiko finally confesses her feelings to him...
 * In Alphas Rachel's powers leave her prone to Sensory Overload, making sex at least very difficult.
 * Nick and Natalie venture into this territory in Forever Knight, because sex and feeding are very much tied together for vampires, and Nick is mostly unable to control himself once he starts feeding. He knows he'd either wind up turning Natalie or more likely, that he'd kill her.

Tabletop Games

 * In both Werewolf: The Apocalypse and Werewolf: The Forsaken,, Werewolves mating with each other tends to have bad results. The Apocalypse gave us Metis, the sterile, deformed offspring of Garou mating - the only "upside" is that they're born in the Wolf Man Crinos form, giving them more power. The Forsaken changes it so that the child of two Urathra is a unihar, a vicious, powerful spirit bent on killing its parents and any Werewolves that get in the way. Though this is more "Can't Have Sex With Own Species"; Werewolves haven't gone extinct yet because they're interfertile with humans (and, in Apocalypse, wolves).
 * Teenagers From Outer Space strongly recommends that the GM derail all attempts by players to get further than, say, first base, by having circumstances interfere in whatever silly fashion they GM can devise, because endless UST is funnier.
 * Darklord Ivana Boritsi of the Ravenloft setting has turned both herself and members of her entourage into ermordenung: living humans whose bodies are permanently saturated with a deadly poison. Ermordenung can't touch anyone normal without killing them, and Ivana cranks up their frustration by using a different poison to create each one, so they'll kill each other if they touch their own kind. Bitch.
 * And any attempts Jacqueline Renier has ends when she inevitably turns into her wererat form and kills them, she can't control this. She also arranges for her sister's lovers to be murdered before they can consummate their relationships out of jealousy (and to keep Louise from usurping her power). Jacqueline's curse only applies if she actually loves her prospective partner. She can have all the casual or Foe Yay sex she wants.

Video Games

 * Both love interests in Planescape: Torment suffer from this. Grace drains the life force of anyone she kisses. Annah heats up to dangerous temperatures once her blood starts racing.
 * And since the main character is immortal, it doesn't matter one bit.
 * Quarians in the Mass Effect universe are generally like this with other races -- thanks to their weak immune systems, sex is dangerous even between two quarians. However, Tali, the quarian love interest in ME2 actively works to subvert the trope if you're romancing her.
 * Turians have a similar issue -- being dextro-amino-based lifeforms, any sort of fluid-exchange could (in a worst case scenario) cause a deadly allergic reaction in either party, and Mordin's repeated warnings of chafing.
 * Some asari are Ardat-Yakshi: they suffer from a condition that fatally burns out the nervous system of anyone with whom they mate. To make matters worse, this also gives the Ardat-Yakshi a boost to their own natural biotic ability, which proves addictive.

Western Animation

 * In Futurama, after members of Zoidberg's species mate, they die. Averted because this doesn't stop them.
 * Truth in Television, as a lot of species die after they mate. Some species of arthropods even eat their mate during or after sex.
 * Also, giant amazons that give you death by SNU-SNU!
 * Brock Samson (of The Venture Brothers fame) can never go past second base with Molotov Cocktease (the only woman he ever loved) because of her chastity belt.

Web Original

 * Artemis, Athena, and Hestia of O-Cast. The first two are more than happy with the arrangement, although Hestia does not seem quite as pleased. In her words: "Forever's a long time to be a virgin."

Webcomics

 * Sam's species in Freefall dies whenever they have sex.
 * They also don't gain full sapience until after the species equivalent of andro/menopause. So their society is made up entirely of those who either couldn't or wouldn't breed when they had the chance.
 * In The Inexplicable Adventures of Bob, it's never been spelled out, but it's been heavily implied that, however effective Voluptua's shapeshifter unit that lets her appear human may be, she and Bob would not be able to do much of anything physical, even if they were so inclined.
 * Deepblooded (drastically mutated) crater hounds in Wurr are not permitted to mate, as stillbirths or Death by Childbirth would likely result.

Fanfiction

 * In the Harry Potter fic Coming Back Late, Harry and Hermione couldn't do anything physical together because even though she was estranged from Ron, their magical marriage vows were "till death do us part". After, this obviously no longer applied.
 * Paul agonizes over this in With Strings Attached, since he's way too strong to dare make love to Linda any more. He is extremely happy when he's depowered at the end of the book.