A "wrong" sound effect that doesn't fit the action portrayed is played [[RuleOfFunny for comedic effect]]. This is for the audience's ears only, the characters never notice in-universe (that would be SoundDefect).

On some shows, this is done routinely and serves to enhance the overall wackiness, on others it is used sparingly and to make a specific auditive point or gag, for example when the impact of a huge object fails to produce the ear-shattering KABOOM sound the audience expects. Typically, 'big' things get a 'small' or silly sound, but the trope works the other way around as well. StockSoundEffects and inherently funny sounds (associated with circuses and clowns) are especially popular. In a common variation, this trope is {{Exaggerated}} by the use of a different Wacky Sound Effect every time an action is repeated, for example when a character [[ComedicSociopathy is repeatedly hit on the head with the same object]].

Sometimes, a sound is played where there shouldn't be anything to hear, for example SqueakyEyes (a subtrope). Contrast with AudibleSharpness and AudibleGleam which aren't considered wacky but rather cross over to CoconutEffect territory. Contrast also with SpaceIsNoisy, where 1) the space noise is also more or less expected by the viewer and 2) the sound effects are pseudorealistic rather than wacky. See also EditorialSynaesthesia.

Another extreme version of this is when something or someone gets a sound effect for just being there or coming into view.

Wacky sound effects are a staple of animation, but also sometimes used in older live-action works where it is likely, however, to be deemed by a present-day audience to feel inappropriate and tantamount to SpecialEffectsFailure. Then, there's the connection to {{Slapstick}} and, by association, to funny home videos.
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!! Examples:

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[[folder:{{Film}} - Live-Action]]
* ''Film/TheManWithTheGoldenGun'' features a ''visually'' impressive RampJump car stunt which is accompanied by a silly cartoony slide-whistle sound.
** Many fans were very upset that one of the most spectacular car stunts in film history was essentially ruined this way, effectively sabotaging the entire chase scene of which the stunt was part. The scene is thus often considered to symbolize everything that many considered wrong about the 1970's Bond films.
* In ''Film/StarTrekIIITheSearchForSpock'', the sabotaged U.S.S. ''Excelsior'''s engines fail with a sound effect that resembles a stalling car.
* In the movie ''Film/{{Airplane}}'', this was coupled with JustPlaneWrong as in-flight shots outside the airliner were accompanied by the sound effect of prop aircraft.
** Not to mention the sound of a ''[[RefugeInAudacity steam locomotive]]'' as it pulled away from the airport terminal.
* In ''MomAndDadSaveTheWorld'', two guards, on orders from Spengo, shoot themselves in the head for their stupidity (they gave him a opinion on facial hair that he did not like). When the do this with their quirky ray guns, one can hear what sounds like a rubber duck being squeezed.
* In ''RepoTheGeneticOpera'', during the song "Thankless Job", several wacky sound effects can be heard.
* ''Monty Python's ''LifeOfBrian'' had a spaceship ([[ItMakesSenseInContext yes, a spaceship]]) that made gearshift noises while in space.
[[/folder]]

[[folder: Live Action Television]]
* StudioC's [[http://www.youtube.com/watch?v=ku_wxcLyQJA Radio Mystery Hour]] starts out fine until the Special Effects gal topples the table with all the special effects things so she has to improvise.
[[/folder]]

[[folder:Western Animation]]
* ''InvaderZim'' had this in spades.
* Done regularly in ''WesternAnimation/LooneyTunes'' cartoons - a gunshot sound for a slamming door, for instance.
* ''SpongebobSquarepants'' has lots of illustrative sound effects to enhance the physicality of the characters: [=SpongeBob=] has both 'woody' (when his arms break off) and 'spongy' (when he walks) sound effects. Also, his facial expressions are quite noisy.
* All spaceships in ''{{Futurama}}'' seem to be fitted with horns.
* ''DrawnTogether'' has lots of these, with Wooldoor Sockbat as the epicenter. His masturbation technique involves a long string of Wacky Sound Effects.
* ''XiaolinShowdown'' does this most often with random, small fart noises during a dumb or stupid scene. When [[TeamPet Dojo]] drinks several bottles of [[BlazingInfernoHellfireSauce hot sauce]] in one episode, he belches out a huge column of soot, and a split-second ''fart sound'' is played.
* In ''Disney/{{Aladdin}}'', when Iago [[GetAholdOfYourselfMan hits Jafar in the head]] it makes a sound that no man's head being hit by a parrot's wing should make. It sounds a little bit like hitting a washing machine.
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[[folder:Video Games]]
* SimFarm gives us some truly bizarre sound effects. Watch [[http://www.youtube.com/watch?v=yF0olK9idsk this guy's]] reactions to them (starting at 1:43).
* Joke weapons in ''SoulCalibur II'' produce Wacky Sound Effects every time they connect: Astaroth's Rock trumpets like an elephant, Yoshimitsu's Shepherd's Crook bleats like a sheep, Necrid's Ethereal Edge makes a "boi-oi-oing" noise, Nightmare's Galley Oar makes a sound like breaking waves, and so on.
* The weapons in ''VideoGame/{{Worms}}'' games sound wacky - because they are.
* In ''TheRingTerrorsRealm'', there's a wacky [="SppplllAAAAT"=] sound effect used throughout the game (it's even used on the menu screens).
-->'''[[TheSpoonyExperiment Spoony:]]''' That was the best sound effect they could come up with, the sound of someone stepping on a mustard bottle.
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[[folder:Web Original]]
* In a {{Garrysmod}} video called "Mass Defect" created by Kitty0706 involves one of two 'fancy' Servant Grunts from ''VideoGame/AmnesiaTheDarkDescent'' saying "Fregley, get into character quick!". Immediately afterward, a WackySoundEffect along the lines of "BAP" plays, they lose their top hats and monocoles, and they proceed to growl like zombies and chase after the 'protagonist'. Link: http://www.youtube.com/watch?v=V46KYxFav24
[[/folder]]
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