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In most fiction, [[NoPeriodsPeriod periods are rarely mentioned]]. SpeculativeFiction normally does likewise, but on the rare occasions that it does mention menstruation, the characters should tremble. Menstruation in SF holds great sway over supernatural powers.

SF periods serve as the trigger for every supernatural menace you can think of. Gruesome BodyHorror is the favorite, but a period can also serve as a source of great power (and [[WithGreatPowerComesGreatInsanity great insanity]]), a magnet for TheFairFolk, a gateway to a hell dimension, or even a semi-sentient RealityWarper. Periods also cause all sorts of supernatural powers, from PubertySuperpower, to [[UnequalRites attunement to magic]]. You're gonna need more than chocolate to sort this one out.

The MenstrualMenace is particularly popular as a MonsterOfTheAesop. Any monster evolving out of a girl's period will serve as an object lesson of how to deal with the [[IncrediblyLamePun pain of puberty.]] If the moral is that GrowingUpSucks, the whole cast will be dead or insane by the end. At the more idealistic end of the SlidingScaleOfIdealismVersusCynicism, defeating the MenstrualMenace will be an {{Anvilicious}} moral about the importance of [[ItsAllJunk abandoning childish things]].

Menstruation in SpeculativeFiction also causes mundane misery and angst, which tend to lead to stupid mistakes that create all of the previous supernatural problems.

The belief systems of some cultures have often incorporated a strong positive or negative supernatural significance to the phenomenon of menstruation.

This trope is for supernatural periods only; for trouble caused by mundane periods, see AllPeriodsArePMS. Compare WomensMysteries. See also HystericalWoman and AllWomenAreLustful, two beliefs brought on by this very trope.
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!!Examples:
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[[folder:Anime & Manga]]
* In ''Anime/ParanoiaAgent'', the problems are all due to [[spoiler: a monster created from Sagi Tsukiko's guilt over a mistake she made while distracted by her first period.]]
* In the first season of ''LightNovel/{{Slayers}}'', Lina Inverse has her powers of magic reduced by 99.9999999% for a few days due to her "Time of the Month", and this happens to ''all'' female magic wielders. It is never mentioned again. (The show turned out to have a larger female audience than expected, and the writers didn't want to offend them).
** This is also the one instance where [[TheDitz Gourry]] understood pretty much immediately the reason behind something being wrong with Lina.
* In ''Manga/{{Karin}}'', the eponymous character has a monthly release of blood...from her nose (unless, of course, she injects it into a human). The similarity to a menstrual cycle is frequently lampshaded, especially in the beginning.
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[[folder:Comics]]
* Grant Morrison's ''Comicbook/DoomPatrol'' has Dorothy Spinner, a mutant who creates {{imaginary friend}}s with her powers. Due to trauma, she acts like she's a little girl. A period is enough to bring back her horrible memories, and the Candlemaker -- a gruesome monster that only children and lunatics can see.
** Artist Richard Case also made sure to draw Dorothy with red shoes, a longtime symbol for menstruation and a woman's maturation.
* Back in the 80's there was a black and white comic called 'MS. PMS'. A woman is infected by an alien device that locks her into a permanent state of PMS; frazzled hair, bad attitude, super-human strength. The aliens were present too, wearing their environmental armor called P.A.N.T.I.E shields. This comic lasted about two issues. [[WidgetSeries Yeah]].
* Alan Moore's Comicbook/SwampThing story, "The Curse," draws parallels between menstruation and the traditional lunar-cycle-based activity of werewolves.
* In UsefulNotes/TheDarkAgeOfComicBooks there was an independent series, ''Crimson Plague'', about a woman whose blood contained a virus capable of wiping out a planet in hours. Cut her, your whole world is dead. And since she's female, leave her alone for a month, you're still dead...
* In ''{{Comicbook/Fables}}'', Frau Totenkinder first began to receive her magical powers after she had her first period ([[OlderThanTheyLook back in the Stone Age]]). It's mentioned that her shedding of blood fueled her powers, however she soon finds that the blood of other children gives her even more power. (Her name ''is'' [[MeaningfulName Mrs. Dead Children]]...)
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[[folder:Film]]
* ''Film/DogSoldiers''. The sole female character quips "It's that time of the month" [[spoiler:as she turns into a werewolf.]]
* During the superhero "tryouts" in the movie ''Film/MysteryMen'', a woman calls herself the PMS Avenger, and "can only work 4 days a month". Her outfit is of course red in color.
--> "You gotta problem with that?!"
* In ''Film/ImGonnaGitYouSucka'', a henchman tries to kidnap the heroine, and she turns into a demon on him. He thinks she's possessed by the devil, but she says, "No! Cramps!"
* ''Film/GingerSnaps'' also makes the menstruation/werewolf connection.
* In ''Film/TheReaping'', a little girl pretty much brings about the end of the world by getting her period. [[spoiler:Or so it seems for awhile.]]
* In the 1993 remake of ''Film/AttackOfThe50FootWoman'', a doctor speculates that Nancy's condition is caused by a hormonal imbalance. Her husband's response is "Congratulations, doctor. You've just discovered a new form of PMS."
* ''Film/TheDevilInside'' has a menstruated and possessed woman spewing her blood at the camera.
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[[folder:Literature]]
* In Suzy [=McKee=] Charnas' short story ''Boobs'', the narrator, when she reaches puberty, changes into a werewolf for several nights per month instead of having periods.
* In the book ''Cycler'' by Lauren [=McLaughlin=], every month before her period the main character, Jill, turns into a boy.
* In Piers Anthony's Literature/{{Xanth}} books, Chameleon changes according to her cycle. At one point in her cycle she is beautiful but dumb, at the opposite point, she is ugly but very smart and clever.
* Inverted in the ''BlackJewels'' series, where witches lose much of their power while menstruating.
* Justine Larbalestier's ''Literature/{{Liar}}'' also connects menstrual cycles and [[spoiler: lycanthropy. There is a excellent scene in the book when the reader is certain that the parents are locking up their daughter for having her period, until it is revealed in the second half of the book that she is a werewolf.]]
* The title character of Stephen King's ''{{Carrie}}'' theretofore mild telekinetic powers become much stronger after her first period starts.
* Characters in ASongOfIceAndFire repeatedly suggest this as an explanation for Brienne's fierce fighting style. Their tone of voice while doing so tends to vary between misogynist mockery (if she's busy or out of earshot) and outright pants-wetting terror (if she's not).
* Nearly every ''Literature/{{Discworld}}'' book in which Angua has a significant role includes a time-of-the-month gag.
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[[folder:LiveActionTV]]
* Parodied in the second episode of ''Series/GarthMarenghisDarkplace.'' The sole female character has a psychotic break, then goes on a telekinetic rampage that kills several people. In the end, all is forgiven because she couldn't help herself -- it was her inevitable female foolishness and hormones (as Thornton Reed puts it, "I think it's her time."). The point, of course, is that Marenghi is a sexist hack who thinks nothing of stealing the plot of ''Carrie'' and making it about how women's issues lead to death.
* In a bit sketch on ''Series/TheYoungOnes'', a young woman is sent to hell and threatened with all sorts of horrific punishments by a (female) devil. Then their dialogue shifts, as the scene is revealed to be a pain-reliever commercial on TV. The young woman goes on about "that strange washed-out feeling you just can't explain", but the devil confides that she's talking about ''period'' pains. Er, so PMS is so agonizing that it's comparable to being ''tortured in hell''?
** [[FateWorseThanDeath If the cramps are bad enough and you have no painkillers ... yes, yes it is.]]
* Played for laughs in ''Series/TheITCrowd'', where Jen's very angry period sees her literally turn into some kind of hell-demon at some points. This results in the image of a red-and-white skinned woman in a business suit screaming things like '''''"I CAN NEVER FIND A BLOODY PEN AROUND HERE!"''''' http://www.youtube.com/watch?v=OgWhT9rDO2g
* In ''Series/BuffyTheVampireSlayer'' Willow tells her new (werewolf) boyfriend Oz "Yeah, okay, werewolf. But three days out of the month I'm not much fun to be around either." Which was a bit of a shock moment, considering how shy and soft-spoken Willow normally is.
* In the sketch comedy show, ''Touch Me, I'm Karen Taylor'', Karen invented the super-heroine Pre-Menstrual Girl, who is the alter ego of normally pleasant and cheerful office worker Penelope. When trouble arises her super-heroine power kicks in: she alters her body-clock and transforms into [[https://www.youtube.com/watch?v=PCVrqV9uFzQ Pre-Menstrual Girl]], a superheroine who saves peoples' lives, either by winning the villain's heart with her neurotic sobbing, or terrifying him into bludgeoned submission by screaming, being aggressive, and sniping.
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[[folder:MythAndLegend]]
* [[OurWerewolvesAreDifferent Werewolf stories]] often have a MenstrualMenace, due to the days in a lunar cycle and a menstrual cycle.
** In the ''Film/GingerSnaps'' films, werewolf transformations serve as a metaphor for not just periods, but every unpleasant body change that comes with puberty. The first film sees Brigitte watching in horror as her sister goes through mood swings, hair on her body in all the wrong places...
** Creator/PeterSBeagle wrote a short story titled ''Lila the Werewolf'' which purposely plays with the similarities between menstruation and lycanthropy.
-->"First day, cramps. Second day, this. My introduction to womanhood."
** Angua is both the first woman and the first werewolf in the [[Literature/{{Discworld}} Ankh-Morpork Watch]], which leads to a misunderstanding early on ("Is it because I'm a w...") Boyfriend Carrot mentions that he tends to stay out of the way around full moon.
* In NorseMythology, [[DaddysLittleVillain Gjalp]] attempted to [[NauseaFuel drown Thor in a torrent of her menstrual blood]] Though in later versions, it's not menstrual blood, but [[{{Squick}} urine]]. In both versions, however, Thor stops the torrent by throwing a rock at her and plugging up... well, yes.
* In Celtic mythology, Maeve (or Medb, or whatever Walisic naming you deem correct) holds back her period (other versions: urine...now where did I heard that before?) until the Big Battle ends. And then it's flood time, too.
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[[folder:WebOriginal]]
* In the ''Literature/WhateleyUniverse'', superpowered mage Fey has her first case of PMS in her first few weeks at SuperheroSchool Whateley Academy. This leads to thunderstorms, lightning bolts and rain. In the dorm hallways.
** For bonus points, all the magical fun ''also'' triggers menstrual discharge in every other girl in the dorm. Including the ones who had just finished with this month's visitor.
* Creator/{{Humon}} has her own Menstrual Monster, which she learned to tame with medical assistance. See '''[[http://humoncomics.com/communists-in-the-funhouse here]]'''
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[[folder:WesternAnimation]]
* And let's not forget Katie Ka-Boom from ''WesternAnimation/{{Animaniacs}}'', who, even though they couldn't say it, was pretty obviously having some major PMS.
** If she wasn't just [[TeensAreMonsters moody and insecure, like a lot of sixteen year olds]], regardless of what time of the month it is.
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* Half-demon Callie in ''WesternAnimation/UglyAmericans'' undergoes "[[FunWithAcronyms Painful Mortal Shedding]]", a process in which a female demon periodically molts her toxic flesh. The agony can only be minimized by near-constant sex with her boyfriend/human sex slave Mark. In the background of another episode, a calendar in Mark's apartment has two weeks marked as "Callie's Period", so apparently that's a bit different for demons, as well.
* There's a joke in the ''KingOfFighters'' Fanon that the only time Leona transforms into her [[SuperpoweredEvilSide Riot]] [[MindControlEyes of Blood]] form is during that time of the month.
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