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There's a Halloween party going on in the Greendale "[[{{Pun}} Liscary]]" and all of the study group are there: Jeff is dressed as David Beckham (complete with stubble and a soccer ball); Britta is dressed as a dragon-turtle ("I'M A T-REX!"); Annie is dressed as Red Riding Hood; Pierce is dressed as [[Series/StarTrekTheOriginalSeries Captain Kirk]]; Shirley is ''not'' dressed as [[Series/TheMuppetShow Miss Piggy]]; and Troy and Abed are dressed as [[Film/{{Aliens}} Ripley in the Power Loader and the Alien Queen]] respectively.

Pierce eats some of the "taco meat" that Dean Pelton bought at an army surplus store and exhibits some strange symptoms, including fever and slurred speech. Soon, he bites Starburns and the infection spreads - resulting in a full blown ZombieApocalypse. And to make matters worse, the Dean locks them in the library to wait six hours for the army to arrive.

Has a [[YMMV/CommunityS2E06Epidemiology YMMV page.]]

!!The ''Series/{{Community}}'' episode "Epidemiology" provides examples of:

* AndThenJohnWasAZombie: Troy is the final survivor, but in the end gets bitten by an infected Abed. The infection begins to take hold, but thankfully Troy is able to turn down the thermostat before it's too late.
* AnguishedDeclarationOfLove: Troy does this to Abed.
* ApocalypseHow: According to Rich, Type 3A within a year and a half. However, seeing as everyone is cured by turning the thermostat down to 58 degrees, one suspects this virus might have a little trouble making it out of Colorado.
* ArsonMurderAndJaywalking: The group is locked in the study room with zombies pounding on the glass doors, the army is six hours away from arriving and Pelton's ABBA mix is playing on a loop over the PA system. But it's not until Pelton's personal reminders get mixed in with the music that Jeff declares it a waking nightmare.
* ArtMajorBiology: The ''physician'' agreeing with Annie's plan to lower the temperature in order to "break the fever and kill the virus". Breaking a fever is all well and good for preventing brain damage, but the fever is the body's defensive response against the virus which was spread among people with presumably normal 98.6 degree temperatures. Bringing them back down to those temperatures they had when the virus was spread in the first place would do nothing against the virus itself, whatever brain damage lowering the temperatures was preventing notwithstanding. The thermostat needs to go at least below 50 F to affect the environment of the virus, by causing hypothermia in its host (it could possibly show up in Pierce and Leonard a bit earlier). And these low temperatures would just be expected to (very slightly) slow the spreading of the virus in the body, not "kill" it (it's pretty hard to kill something that isn't especially alive in the first place). The average virus would still be active, much less capable of reactivation, long, long after the human has died of hypothermia. There is a reason fevers and sterilization techniques use ''high'' temperatures, not low ones.
** Keep in mind that this whole episode is about a [[RuleOfCool zombie epidemic from taco meat]].
* BigBudgetBeefUp: This is by far one of the series' most impressive and expensive episodes. The ABBA songs alone ate up the entire season's music budget.
* [[BigDamnHeroes Big Damn Hero]]: Troy, cooling everyone down until the military arrived.
* BigNo: Troy, when Abed gets DevouredByTheHorde.
* BlackAndNerdy: This episode actually {{deconstruct|ion}}s it for Troy. Hanging out with Abed has turned him from a JerkJock who could get ladies easily, into a huge nerd. This leads to his brief foray into being a sexy Dracula, however at the end he realizes he values Abed's friendship more. And even though he's roofied at the end like everyone else he seems to have absorbed this lesson.
* [[BlackDudeDiesFirst Black Dude Gets Zombified First]]: Intentionally inverted -- Abed saves Troy and sacrifices himself in hopes that Troy could be the first black guy to actually make it to the end and save everyone. It works.
-->'''Abed:''' Troy, make me proud. Be the first black man to make it to the end.
* BloodyHandprint: Troy leaves one on the air con panel.
* BloodyHilarious: [[Film/ShaunOfTheDead Another]] zombie apocalypse played for laughs.
* BondOneLiner: Troy gets out a few, before running out of ideas.
* BrainwashResidue: Even though the MemoryWipingCrew did their job, it would appear everyone subconsciously remembers what happened ''to some extent'', as Jeff states his skepticism over the cover story (Everyone at the party was roofied) whilst Troy & Abed decide they don't want to watch a zombie movie as they feel zombies are played out, but can't remember why.
* ButtMonkey: Starburns is the first to get bit, as per usual.
* CatScare: Parodied:
-->''(Screeching cat flies past camera.)''\\
'''Jeff:''' Jesus! Haha, it was just a cat. Letís keep moving.\\
''(Screeching cat flies in opposite direction.)''\\
'''Troy:''' Holy crap!\\
'''Jeff:''' What is up with that cat?!\\
'''Abed:''' Keep moving!\\
''(And again.)''\\
'''Jeff:''' Letís not keep moving, because there is an insane cat down here!\\
'''Troy:''' What about the zombies?\\
'''Jeff:''' [[SkewedPriorities Back burner, Troy! This cat has to be dealt with.]]
** As a bonus, the cat is the same breed as Jonesy, the TropeNamer from ''Film/{{Alien}}''.
* TheCavalryArrivesLate
-->'''Dean Pelton''': Six hours, on the dot!
-->'''MIB''': We've had a lot of practice.
* ContinuityNod:
** Rich from "Beginner Pottery" shows up again (and Jeff still hates him).
*** He also ends up infecting the study group after hiding his zombie bite. He thought he might be special - despite the fact that we know from "Beginner Pottery" that his mother repeatedly told him he wasn't.
** In a later episode, Troy shows attention to the fact that Shirley ovulates on Halloween. (ItMakesSenseInContext) So this episode might actually influence future episodes.
** In "[[Recap/CommunityS1E07IntroductionToStatistics Introduction to Statistics]]," Shirley's Halloween costume is repeatedly mistaken for Urkel due to her race - she's actually Harry Potter. One of the people who makes that mistake is Chang. In "Epidemiology," Chang dresses as ice skater Peggy Fleming, and is repeatedly mistaken for Kristi Yamaguchi and Michelle Kwan due to his race. In his case, it's on purpose - he's the racist prover. Shirley is one of the only people who is able to tell who he's supposed to be.
*** Annie also references the fact that Shirley's worn an 'unintentionally ambiguous costume' for the second year in a row - she's Glinda the Good Witch, not Miss Piggy. Chang is the only person to realize this - a fact which leads to their hooking up.
** A nod to Chang's [[Recap/CommunityS1E02Spanish101 first appearance]].
-->'''Chang''': Ya bit? YA BIT?!?
** The Dean [[Recap/CommunityS1E20TheScienceOfIllusion still uses pepper spray]].
* CreepyBasement: Jeff, Troy, and Abed make their way here when escaping from the zombies.
-->'''Jeff:''' Oh great. [[LampshadeHanging A dark basement]]. I was just thinking we should be doing this in a dark basement.
* CuttingCorners: The Dean's idea to buy (what seems like) food from an army surplus store backfires when the content turns out to be toxic waste [[ToxicWasteCanDoAnything potent of inducing]] a ZombieApocalypse.
* DangerousWindows: Annie is wrestled out a window by a zombie horde.
* DeathByMaterialism: Okay, not an actual death, but otherwise played straight. Jeff would rather walk into a door with zombies potentially on the other side rather than climb out a window and wrinkle his suit.
* DevouredByTheHorde: The assimilation of Annie, Jeff, Abed and lastly Troy.
* DiscontinuityNod: In-universe. At the end, Troy and Abed are going to watch a movie, at first considering a horror film, but decide that they are "over zombies" and watch ''Film/{{Marmaduke}}'' instead.
* DramaticSlip: Shirley when running from the zombie horde. She is helped up by Chang.
-->'''Jeff''': Don't look back!
-->'''Shirley''': Why not? - Oh! (stumbles)
* DwindlingParty: One after the other ofthe group gets zombified.
* EverythingIsRacist: Senor Chang deliberately dressed as Peggy Fleming so he could prove everybody is a racist (for example, Britta guesses Kristi Yamaguchi). Because he's the racist prover. Shirley, though, figures out who he is on the first guess (and likewise, Chang figures out that Shirley is [[Film/TheWizardOfOz Glinda the Good Witch]] on the first guess).
* FamousLastWords: Before they turned to zombies.
** "Jeez, why don't you two just get a room?" - Starburns
** "Special? You're not special! I'M special! I was bitten ten minutes ago and I'm fine!" - Britta
** "What the hell?!" - Annie
** "My suit! You're stretching it! Stretching it!!!!!" - Jeff
** "Shirley and I totally did it!" - Chang
** "Make it fast." - Abed
** "Jeff: still cool as a zombie." - Troy
* FreezeFrameBonus: If you look closely at the packaging, the taco meat not only states it is a 'biohazard', but it also shows a [[http://vignette4.wikia.nocookie.net/community-sitcom/images/5/5d/Classified_Phoenix.png/revision/latest/scale-to-width-down/640?cb=20120713163029 pictogram]] showing that if you eat it, you will turn into a zombie.
* GenreSavvy: Troy and Abed immediately label the infected as "zombies"; Chang throws a skate at them, declaring they must [[RemovingTheHeadOrDestroyingTheBrain destroy the brain]].
* HalloweenEpisode
* HeroicSacrifice: Abed & Troy pull two separately.
* {{Homage}}: There are several shot-for-shot recreations of ZombieApocalypse media.
** Annie is [[DangerousWindows wrestled out a window]] by a zombie horde in a recreation of a shot from ''Film/ShaunOfTheDead'', which is itself a recreation of a similar shot from ''Film/DayOfTheDead1985''.
** Troy and Abed climbing atop the storage shelves in the basement is a reference to the video game ''VideoGame/DeadRising'', and Jeff's threatening them with a raised soccer ball (using [[ImprovisedWeapon Improvised Weapons]], including soccer balls, are a gameplay mechanic) might be as well. The Army's six hour delay matches the play time of the main storyline.
** The Army makes the Dean quarantine the Halloween party just like it quarantined the apartment complex in ''Film/{{REC}}''.
** The explanation of the 'zombies' as infected by rabies pokes fun at both ''Film/TwentyEightDaysLater'' and the American remake of ''Film/{{REC}}'', ''Film/{{Quarantine}}''.
** Jeff's taken in by zombies like Barbara near the end of the original ''Film/NightOfTheLivingDead1968''.
** Troy and Abed repeating the famous "I love you."/"I know." scene from ''Film/TheEmpireStrikesBack''.
** Abed is eventually crushed against the wall in a fenced-in storage area by a wall of zombies in a repeat of the shot from ''Film/IAmLegend''.
* {{Hypocrite}}: One of the reasons the study group hates Pierce is for seeing them one-dimensional stereotypes. This episode we find out they do a [[{{Flanderization}} Flanderized]] impression of him behind his back.
* ImNotADoctorButIPlayOneOnTV: Annie starts to seek help from a young man dressed up as a doctor after Pierce becomes sick, before asking the doctor dressed up as a banana.
* ImprobableWeaponUser: Jeff, whose costume is David Beckham, uses his soccer ball to take out a ''zombie''.
* InstantSedation: The Dean goes out instantly after being dosed by the MenInBlack.
* KillEmAll: Plan A.
* LampshadeHanging: It's ''Community'', so... a lot. But in particular, the CatScare and Jeff's comment that he was hoping they could do this in a dark basement.
* LethallyStupid:
** Quite predictably, the Dean falls into this. He bought ration tins full of biohazard material from a military surplus store and assumed it was taco meat with a goofy label. The biohazard warning signs and the large label "Do Not Open" [[FailedASpotCheck should have tipped him off]].
** Chang's attempt at fending off the infected ended in Annie dragged off by zombies and their only sanctuary compromised.
* MayanDoomsday: Brought up, but Chang shoots it down since it's currently 2010. When Rich hypothesizes that the infection would fully spread around the world in a year and a half, Chang realizes that it would be 2012 by the time that happens, leading him to panic and think the 2012 apocalypse is in play after all.
* MemoryWipingCrew: Plan B, dose everyone so they [[LaserGuidedAmnesia don't remember anything from the zombie apocalypse]].
* TheMenInBlack: At the very end, they roofie everyone so they'll forget.
* MilitariesAreUseless: The army makes a ''point'' out of showing up six hours after the first news of infection. Also, they apparently didn't think of a cure that a doctor in a banana suit and a college student in a Red Riding Hood costume casually hypothesized. Not to mention that they seem prepared to eliminate a school full of people because they have a virus that can't survive sub-60 degree temperatures.
* TheNarrator: Opening and closing narration, most of which is irrelevant to the episode, is provided by Creator/GeorgeTakei as himself.
-->'''George Takei:''' And so, Troy and Abed went back to the dormitory for a viewing of ''Film/{{Marmaduke}}''. I'm George Takei, and if your name is Kevin, here's a little freebie for your cell phone. Hi, Kevin can't come to the phone. [[FunnyAnsweringMachine He's on a spaceship with me, George Takei.]] Please leave a message. You're welcome, Kevins. Happy Halloween.
* [[NiceJobBreakingItHero Nice Job Getting Annie Infected]]: Chang.
* NotAZombie: For a long time, characters are oblivious to the zombie infection going on, partly driven by the fact that they are [[ForHalloweenIAmGoingAsMyself at a Halloween costume party]].
* NowOrNeverKiss: Between Shirley and Chang in the bathroom while being surrounded by zombies.
* OrWasItADream: At the end of the episode, Troy receives a hint that more happened than just being roofied for no reason in the form of a [[DeadManWriting voice mail]] sent during the night by Chang, claiming he and Shirley did it in the bathroom.
** Troy [[DramaticallyMissingThePoint doesn't understand the relevance]], only wondering why Chang would tell ''him'' about it despite the sounds of the zombies attacking at the end.
** There are repercussions of Chang and Shirley's tryst in subsequent episodes.
* OutOfCharacterMoment: While it may be attributed to the high stress of the situation, you have to wonder why the self-righteous Shirley who has a rather negative opinion of Chang would sleep with him.
* OutOfGenreExperience
* PantyShot: Chang throws his skate, breaks the window, zombies grab Annie, pick her up and carry her out of the room, allowing the viewer a glimpse of Allison Brie's naughty bits under her Red Riding Hood skirt. It's so brief it's almost subliminal but noticeable enough to make you go "wait, was that...?".
** According to the commentary, that was the shot with the ''least'' amount of visible panties.
* PatientZero: Pierce is the first confirmed infectee from eating the taco meat. It's unclear how many others may have eaten some (perhaps Pierce ate all of it) but he is visibly the first to start displaying symptoms and biting people.
* ThePowerOfImagination: Thoroughly subverted. "That's right. Prepare to meet the power of imagination." "Why did I think this would work!"
* RealityEnsues: Troy decides to use "ThePowerOfImagination" and put on his power loader costume to fight the zombies. He immediately gets held down thanks to it and the costume is torn apart.
* ResetButton: The end when the military comes in and [[MemoryWipingCrew wipes everyone's memories]]. Partially subverted, since the Chang/Shirley hookup became a major plot point later on.
* RoomFullOfZombies: In the basement, Jeff obliviously opens a door behind which horde of zombies were waiting.
* ShedArmorGainSpeed: Parodied. At the climax, Troy dons his Halloween costume: a cardboard version of the power loader from ''Film/{{Aliens}}''. While it does give him a little bit of protection from the [[TechnicallyLivingZombie Technically Living Zombies]], it also gives them more to grab onto and slows him down. He quickly sheds it and wonders why he thought that it would be a good idea.
* ShipTease: Abed/Troy (see Homage section); Annie/Rich; Chang/Shirley (the most overt)... Shirley/Leonard?
* ShirtlessScene: Troy decides to change costumes to be a "sexy Dracula," which mainly consists of him without a shirt and wearing a toilet seat cover around his neck that says "Dracula", for enough time to almost qualify him as a WalkingShirtlessScene.
* ShoutOut: Many, many. Too many to remember. In particular, several glib references are made about everyone's costumes.
** One semi-obscure one: Jeff calls 911 and can't get through, and comments that "Flava Flav was right" - referencing Music/PublicEnemy's song "911 Is A Joke."
** Chang makes a joke about how he didn't mass-roofie people. Now [[Film/TheHangover what else has he appeared in which involved mass-roofieing?]]
* SkewedPriorities: Used three times.
** Right before zombies swarm the study room, Jeff asks if anyone managed to turn off the Dean's ABBA playlist.
** When they abandon their plans of escape to resolve the CatScare issue.
** When Jeff is about to be zombified, all he's scared of is ''Rich stretching his suit jacket''. A situation he only ended up in because he wouldn't climb over the dusty fence in his suit.
* SomethingElseAlsoRises: Pierce raises the lower part of Rich's banana costume while he was flirting with Annie.
* SoundtrackDissonance: The Dean's Music/{{ABBA}} playlist plays throughout the entire episode. And it is [[CrowningMusicOfAwesome awesome]].
* SpecialEditionTitle: The opening credits [[https://www.youtube.com/watch?v=vIbkJ9elpNo have been Halloweenified]]! Featuring some interesting in-jokes (if you listen to the commentaries on the first season [=DVDs=]).
** VisualPun: Within these credits, Shirley's actress's credit appears with a picture of a ''mummy''. And Chang's credits are... [[TheIllegal aliens in mexican hats.]]
* StockScream: The Wilhelm is heard when Troy re-enters the zombified party in the Power Loader.
* SuspiciouslyAproposMusic: The line "There's something in the air tonight" from ABBA's "Fernando" plays when the air con kicks in and cools down the building.
* TakeThat: The show deals another TakeThat to William Shatner by having Pierce dress up as [[Franchise/StarTrek Captain Kirk]].
-->'''Jeff:''' Whoa, if you get any more sweaty and puffy, your costume's going to take on new levels of authenticity.
* TechnicallyLivingZombie: Mixed with {{Flesh Eating Zombie}}s and {{Plague Zombie}}. People don't go from alive to dead to undead, they get zombified to a high fever that's caused by eating infected taco meat and then spread to other people by biting each other.
* ThatPoorCat: In keeping with the Troperiffic nature of the episode.
* TheyPlottedAPerfectlyGoodWaste: Let's be honest. No one expected this to be more than a one-off joke, especially when everyone ended the episode without their memories. Then Shirley and Chang's hook-up becomes a major plot point, as well as the fact that they don't remember it adding drama to the overall story.
* ThisIsNoTimeToPanic:
-->'''Annie:''' We need to co-ordinate an orderly evacuation without causing unnecessary panic.\\
[''Zombie!Leonard bites someone'']\\
'''Troy:''' '''HOLY CRAP, LEONARD'S A ZOMBIE!!!'''
* TooDumbToLive:
** Troy not only tries to use a cardboard Powerloader as armor, but he laters tries to IKnowYoureInThereSomewhereFight with zombie-Abed.
** Jeff [[SkewedPriorities worries more about his clothes than the threat of zombies.]]
** Both [[ZombieInfectee Britta and Rich]] thought they were special enough to be TheImmune.
** Later, when the Army finally arrives, they ask the Dean if he's [[DoesAnyoneElseKnow the only witness]] while cocking their guns and he quite happily states that he is.
* TimeForPlanB: The army's Plan A is NukeEm but they are quick to fall back on [[MemoryWipingCrew Plan B]] when they see that the infection has actually worn off.
* ToxicWasteCanDoAnything: The Dean gets biohazardous material from an army surplus which causes a ZombieApocalypse.
* VampiresAreSexGods: Troy tries to invoke this when he changes out of his Power Loader costume into a "sexy Dracula" costume, hoping he'll attract more girls that way.
* TheVirus: A nameless, bizarre version causes the near-{{Zombie Apocalypse}}.
* WalkingShirtlessScene: Troy's "Sexy Dracula" costume.
* WeveGotCompany: Invoked by name.
-->'''Abed:''' I hate to be the '[[WeveGotCompany we've got company]]' guy, but...
* WouldHitAGirl: Jeff and Troy, if that girl were a zombie.
-->'''Troy''' "You punched a lady bee!"\\
'''Troy:''' "Hey Annie, what nice fists you have... IN YOUR FACE!" *punch*"
* WrongGenreSavvy: Troy using ThePowerOfImagination to try and defeat the zombies with his Power Loader costume. The zombies quickly remind him that ThisIsReality.
* ZombieApocalypse: Thanks to Troy and Dean Pelton, stopped before it got out of Greendale.
* ZombieInfectee: Rich (from "Beginner Pottery") and Britta both try to hide the fact that they were bitten by a zombie. It doesn't take long for the infection to ruin their cover.