Sometimes people are so tense it doesn't take much to scare them. Cue either a smarty alec team-mate or a foe with the taste for irony simply stating "Boo". This results in the jittery character either freaking out or begin running in a panic while screaming. Usually a ComedyTrope but appears in genuinely scary works to show how threatening the monster/villain's presence is.

Compare CherryTapping which is a minor attack downing someone rather than a minor spook and TheLastStraw.

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!!Examples:

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[[folder:Anime & Manga]]
* In Episode 2 of the ''Anime/LittleLulu'' anime, Lulu says "Boo" to Tubby in a deadpan tone while pretending to be a monster, which sends Tubby running off [[ScreamsLikeALittleGirl screaming in terror.]]
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[[folder:Comic Books]]
* The Scarecrow pulls this on Judge Death in "Judgement on Gotham", a Franchise/{{Batman}}/ComicBook/JudgeDredd crossover comics. Death is ''not'' amused...
* Christopher Champion (Tempest) pulls this on a guard at a museum where the ''Scanner One'' spaceship was stored in the ''ComicBook/AtariForce'' series.
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[[folder:Comic Strips]]
* In ''ComicStrip/BloomCounty'', wheelchair-bound Vietnam vet Cutter John is having tea with his girlfriend's mother. He asks if she's nervous, since some people are nervous around the handicapped. She, smiling, says no. Last panel is him saying "Boo." and her tossing her tea and shielding herself.
* In one Halloween comic strip of ''ComicStrip/{{FoxTrot}}'', Jason dresses up as a ghost and practices booing. The problem is that he's booing not like a ghost, but like a dissatisfied spectator.
* ''ComicStrip/USAcres'': the original strip has an example of Roy trying this on Wade after tying his beak up.
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[[folder:Fan Works]]
* In ''Fanfic/{{Kage}}'', [[HeroWithBadPublicity Jade]] does this to [[LovableCoward Blunk]] when they first meet face-to-face.
* In ''Fanfic/TheNewAdventuresOfInvaderZim'', Norlock pulls this on Dib when they meet for the first time after Norlock follows him and Zim back to Doomsville. He sneaks up on Dib at Parent Teacher Night and when Dib turns around and sees him, merely says "Boo". Dib ends up shrieking like a monkey and scuttling away.
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[[folder:Films -- Animation]]
* Shan-Yu greets the Emperor this way in ''Disney/{{Mulan}}''. Played for scares, though [[TheStoic the Emperor himself]] does not freak out.
* ''Film/SpaceJam'', after the Nerdlucks transform into the Monstars.
-->'''Blanko:''' Hey, little pig... boo.\\
'''WesternAnimation/PorkyPig:''' AAAAAAAAHHHHHHHHH! ''[{{beat}}]'' I w-w-w-wet myself.
* In ''WesternAnimation/{{Madagascar}}'', after Alex fights off the fossa, he scares off the few that remain standing with a simple "boo".
* In ''WesternAnimation/BatmanAssaultOnArkham'', after escaping from his cell, ComicBook/TheJoker simply walks out of the shadow toward a warden and says "Boo." This being [[TheDreaded The Joker]], of course, the warden seriously freaks out.
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[[folder:Films -- Live-Action]]
* The live-action ''Film/{{Casper}}'' movie has the clock strike 8 o'clock, showing Casper's a ghost. With a little "Hum, boo?" the entire party flees Whipstaff Manor.
* ''Film/HowTheGrinchStoleChristmas'' has the titular character give a little "boo" when he shows up in Whoville to collect the Holiday Cheermeister award. The gathered crowd screams, which the Grinch responds to by saying "Hot crowd."
* Used by the Lunar Ghost in the first ''Film/ScoobyDoo'' live-action movie. Naturally, Scooby screams.
* ComicBook/TheJoker Pulls this on Vicki Vale in ''Film/{{Batman}}''. [[TheDreaded Understandably,]] Vicki screams.
* ''Film/UndercoverBrother''. When Lance gets into the limousine next to James Brown he's clearly nervous. James Brown says "Boo" to him and he almost jumps out of his skin.
* Played with in ''Film/{{Ghost}}'', where the title character freaks someone out by writing "BOO" on his mirror. Considering that Sam is, well, [[ExactlyWhatItSaysOnTheTin a ghost]], and the person he's freaking out is watching the word trace itself into a fogged mirror, it's not really a "minor" scare at all.
* In ''Film/TheNinthGate'', Boris Balkan does this after killing Liana in front of her coven, making them all jump.
* In ''Film/PetesDragon1977'', Elliot does this to Hoagy the second time they meet, when Hoagy comes to deliver the message that Pete's been captured.
* In ''Film/DoctorStrange'', Christine gets a face full of the supernatural as she attempts to keep Strange alive while he battles a villain in the Astral Plane. After ghosts, poltergeist-like disruptions, and a magical portal in front of her very eyes, she's scared witless by a broom falling to the floor.
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[[folder:Literature]]
* The main character in ''Literature/EdenGreen'' concentrates so hard on aiming her gun into the shadows, she doesn't notice the playful psychopath Tedrin sneaking up on her until he whispers, "Having fun yet?" This gets him shot.
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[[folder:Live-Action TV]]
* ''Series/MysteryScienceTheater3000'': When Mike and the 'Bots have ''The Screaming Skull'' inflicted upon them, Crow decides to pull a prank on Mike -- dressing up as a skull and giving a feeble "raaar." The resultant meltdown by Mike [[https://www.youtube.com/watch?v=zKL_8IKpnp4 has to be seen to be believed.]]
* ''Series/{{Bones}}'': Temperance Brennan playfully says "Boo!" to a security agent at an airport... just as he finds a human skull in her bag. It works.
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[[folder:Puppet Shows]]
* In ''Series/SesameStreet's'' "News Flash" take on Little Miss Muffet, the spider appears to know [[http://www.youtube.com/watch?v=hSe6pg8zsqk this one]].
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[[folder:Video Games]]
* In ''VideoGame/{{Spyro}} 2'' [[BigBad Ripto]] does this to Moneybags [[TemptingFate right after Moneybags said he'd give Ripto a piece of his mind if he was there.]]
* In ''VideoGame/Halo2'', the Master Chief does this after the Gravemind teleports him into ''High Charity'' and he finds himself standing right next to a very startled Grunt. The Grunt reacts by screaming in terror, throwing his gun, and running away. The MC then calmly grabs the gun and begins fighting his way through the Covenant capitol.
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[[folder:Web Comics]]
* Variation in ''Webcomic/BrawlInTheFamily''. Dedede and Meta Knight are stuck together by a Gooey Bomb and as Dedede is sweating Meta Knight flatly says "Boom" to get a rise out of Dedede.
* ''Webcomic/GunnerkriggCourt'' on page 153, when Mort tries to sneaks up on Kat and Annie sneaks up on him.
* In ''Webcomic/PunchAnPie'', Angela comes home to [[http://punchanpie.keenspot.com/daily/20071217.html this]] when she meets Erik for the first time.
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[[folder:Web Original]]
* [[http://cheezburger.com/2114563840 This page]] at WebOriginal/{{Lolcats}}.
* ''WebAnimation/RWBYChibi'': When Jaune is making an ASMR video, he doesn't notice Nora creep up behind him. She takes a deep breath as if she's about to yell in his ear, but instead very softly says "Hi". Jaune freaks out and jumps like cat in response.
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[[folder:Western Animation]]
* In the Creator/TexAvery cartoon "Slap-Happy Lion", a mouse scares a lion with a flat boo. Doing it repeatedly drives the lion mad.
* ''WesternAnimation/{{Droopy}}'', given his knack for OffScreenTeleportation, has done this a few times.
* Variant in ''WesternAnimation/TwoStupidDogs''. The big dog will scare cats by going to up to them and giving a deadpan "Woof." The cat will then comically seize up in fear.
* In the ''WesternAnimation/USAcres'' episode "I Like Having You Around", Wade tries to convince a bug that he's not afraid of him. However, the bug just says "Boo" to him in this manner, causing Wade to freak out and run in a panic.
* Raven does this to Beast Boy in an episode of ''WesternAnimation/TeenTitans''.
* This was also exhibited in the first act of the ''WesternAnimation/MrBogus'' episode "[[Recap/MrBogusS2E4BookstoreBogus Bookstore Bogus]]" with a pair of ferocious worms that Bogus encounters in a book about bugs. When Bogus claims that he's not afraid of them, the worms look at each other for a few seconds before saying "boo" to Bogus in this manner, causing him to run in a panic with the worms hot on his tail.
* In a first season episode of ''WesternAnimation/TheVentureBrothers'' 21 threatens Brock Samson with a lightsaber. After finding out the beam isn't solid, Brock leans in close and says "boo" making 21 run away. 3 seasons later after 24 TookALevelInBadass, Brock tries to do the same thing, and ends up getting round house kicked in the face.
* Chow does this to Tohru in ''WesternAnimation/JackieChanAdventures'' when he gets the first Oni Mask. Tohru, who has an immense fear of the Oni, freezes in terror before Jade tells him to snap out of it. Tohru later returns the favor when the mask is removed, and Chow flees with his tail between his legs.
* On one ''WesternAnimation/SpongeBobSquarePants'', [=SpongeBob=] and Patrick claim that they weren't frightened by a scary movie. A flat boo from Squidward proves otherwise.
* An episode of the ''WesternAnimation/{{Beetlejuice}}'' cartoon has Lydia's friends look into the hollow of a tree they believe to be haunted. Beetlejuice calmly says, "Hey, how ya doin?" Lydia's friends flee in terror.
* ''WesternAnimation/MyLittlePonyFriendshipIsMagic'':
** In "[[Recap/MyLittlePonyFriendshipIsMagicS6E16TwentyEightPranksLater 28 Pranks Later]]", Rainbow Dash uses a simple "boo!" twice:
*** First on Fluttershy in the opening, after having already scared her good with a dragon disguise. She's so jumpy already that she springs away and clings to a branch like a tree sloth.
*** Then on Pinkie Pie, while upside-down inside her closet. Pinkie finds it hilarious.
--->'''Pinkie Pie:''' She got me gooooood.
** "[[Recap/MyLittlePonyFriendshipIsMagicS6E18DungeonsAndDiscords Dungeons & Discord]]": In the RPG world, as "Garbunkle" and "[=Sir McBiggen=]" are fleeing from the Squizard inside a cave, Discord suddenly shows up upside-down and says "Boo!" Spike and Big Mac scream.
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