History Main / HybridOverkillAvoidance

** The ''TabletopGame/OldWorldOfDarkness'' has similar rules to the above to prevent gratuitous crossover, and to encourage players to make their characters distinctive through good character development and not just (to quote one of the designers) [[SpecialSnowflakeSyndrome "having a grab bag of powers no one else has"]]:
*** Only humans have avatars, so only humans can Awaken to become Mages. Becoming undead of any kind gets rid of the avatar, nixing that option. Shapeshifters were born as shapeshifters, Umbral spirits in fleshly form, even if they resemble humans or animals at birth, so they lack avatars. When they die they go to a different kind of afterlife than human dead, so they can't become [[TabletopGame/WraithTheOblivion wraiths]], zombies, or TabletopGame/KindredOfTheEast.

* ''TabletopGame/TheWorldOfDarkness'' games enforce this trope for balance issues. Hypothetically, though, any supernatural that can be changed back to human can be turned into another type.

* ''Manga/MonsterMusume'' confirms that any child of a monster/human pairing is an apparently un-hybridised monster, this being the only thing that allows certain one-gender species to survive. [[spoiler: Mia, Papi, and Centoria]] are all examples.

* ZigZagged in ''Literature/TheSanguineChronicles'' where, like ''Film/Underworld2003'', being one immunizes you from the other. Marko is, however, [[SingleSpecimenSpecies a VERY rare aversion]].

* In ''Young All Stars'', there's an Axis agent called Sea Wolf, a water-breathing werewolf.

** The ''TabletopGame/OldWorldOfDarkness'' has similar rules to the above to prevent gratuitous crossover, and to encourage players to make their characters distinctive through good character development and not just (to quote one of the designers) "having a grab bag of powers no one else has":

%%* The [[AvertedTrope aversion]] of this is a major plot point in [=IDW's=] CrisisCrossover ''Infestation''. The [=US=] government decides the best way to deal with a scientist accidentally opening a portal to a zombie dimension is to send in their vampire agents backed by robots. Unfortunately, [[OurZombiesAreDifferent this particular zombie outbreak]] ''did'' affect vampires and robots. [[OhCrap Oops.]] Cue one zombie plague spreading to the worlds of ''Franchise/StarTrek'', ''Comicbook/GIJoeIDW'', ''Comicbook/{{Ghostbusters}}'', and ''{{Transformers}}''. That's right, there were zombie Transformers.
%%** [[spoiler: Britt's Transformer form]] is effectively a [[NinjaPirateZombieRobot Ninja Vampire Zombie Robot]] (insofar as [[spoiler: CVO agents]] count as ninjas).
%%* ''ComicBook/BuffyTheVampireSlayer'' post-show comics:
%%** Averted in one instance in ''ComicBook/BuffyTheVampireSlayer Season Eight'': the minor villain Kumiko is a vampire witch.
%%** Also averted in Season Nine in which the BigBad, Simone Doffler, is a rogue Slayer who experiments with deliberately getting other Slayers turned by vampires to investigate the possibilities. She finally makes the upgrade herself, but is soon killed by Buffy.

%%* Averted in ''Zombillenium'': Two managers (a werewolf and a vampire) each need an extra werewolf/vampire, so they grab the new guy and bite him to suit their need and try to counteract the other monster's bite. As a result, the guy ends up a BigRedDevil instead and the theme park's new star attraction.

%%* Averted in ''Film/TheMonsterClub'', where Creator/VincentPrice's vampire character explains the elaborate range of existing hybrids between ghouls, vampires, and werewolves. The first of the [[AnthologyMovie stories he tells]] is about a "shadmock", the result of [[HeinzHybrid generations upon generations of hybridization]]. In monster society, shadmocks are looked down upon, but they are also uniquely dangerous.

%%* An aversion. In some parts of Europe, it was thought at one time that the corpses of werewolves would rise as vampires if they weren't cremated. In other parts, the corpses of dead sinners were said to become blood-drinking wolves at night. In Serbia, werewolves and vampires are collectively referred to as the same creature.

*** [[TabletopGame/VampireTheRequiem Vampires]] are dead humans resurrected to unlife by an as yet unexplained but likely magical force. [[TabletopGame/ChangelingTheLost Arcadia]] will not mutate them because, to borrow a line from ''Series/DoctorWho'', they are facts, in the metaphysical sense: they cannot change. They are stuck the way they are, and nothing (about the twisted nature of the Fae realm - let's just ignore the Ordo Dracul for the purposes of this discussion) will ever change that. They were human; they were not created, whether [[TabletopGame/PrometheanTheCreated by man]] or the [[TabletopGame/DemonTheDescent God-Machine]]. They already have powers, so the desperation to take up [[TabletopGame/HunterTheVigil the vigil]] never comes to them. [[TabletopGame/WerewolfTheForsaken While Luna may be mad]], she does not bestow her gifts upon the undead, even if they were wolf-blooded in life. Similarly, [[TabletopGame/GeistTheSinEaters geists]] bargain with the newly dead they can restore to life, rather than the undead. [[TabletopGame/MummyTheCurse The Rite of Return]] was last enacted over six thousand years ago, and there's no-one alive who knows how to perform it - not to mention the question of whether it would work on the undead. Lastly, not having the spark of true human life anymore, they can't [[TabletopGame/MageTheAwakening awaken to true magic]], and have lost the deep connection to the Primordial Dream that would [[TabletopGame/BeastThePrimordial allow a primal nightmare to replace their soul]].

*** One exception is a [[TabletopGame/VampireTheMasquerade vampire]]-[[TabletopGame/WerewolfTheApocalypse werewolf]] hybrid "abomination," extremely tricky but possible. Werewolves are violently allergic to vampire blood so if you try to 'embrace' one, he gets a roll to see if he died peacefully or in horrible pain. Unless they're out of all Willpower, they get to die automatically. A hybrid is created only if you [[CriticalFailure botch]] that roll. A hybrid does have access to all the powers of both but has to watch the KarmaMeter very carefully - from a spiritual point of view, werewolves and vampires are pretty much opposites (one being a nature spirit that just happens to have flesh while the other is a dead shell with barely any spiritual presence) so straining too far will be detrimental to all spirit-related powers. Their Gnosis now functions like a normal vampire's Humanity and goes down from actions unbecoming of a Garou. They retain their old Gifts but can no longer learn any new ones except from corruption spirits. And if their Gnosis runs out, they go into a mindless rage until someone or something inevitably puts them down. That's if they get to that point, of course - plenty of both vampires ''and'' werewolves will put them down just for existing, especially the latter.

*** One exception is a [[TabletopGame/VampireTheMasquerade vampire]]-[[TabletopGame/WerewolfTheApocalypse werewolf]] hybrid "abomination," extremely tricky but possible. Werewolves are violently allergic to vampire blood so if you try to 'embrace' one, he gets a roll to see if he died peacefully or in horrible pain. Unless they're out of all Willpower, they get to die automatically. A hybrid is created only if you [[CriticalFailure botch]] that roll. A hybrid does have access to all the powers of both but has to watch the KarmaMeter very carefully - from a spiritual point of view, werewolves and vampires are pretty much opposites (one being a nature spirit that just happens to have flesh while the other is a dead shell with barely any spiritual presence) so straining too far will be detrimental to all spirit-related powers. Their Gnosis now functions like a normal vampire's Humanity and goes down from actions unbecoming of a Garou. They retain their old Gifts but can no longer learn any new ones except from corruption spirits. And if their Gnosis runs out, they go into a mindless rage until someone or something inevitably puts them down. That's if they get to that point, of course - plenty of both vampires ''and'' werewolves will put them down just for existing.