History ThrowItIn / WesternAnimation

** Haru's [[MemeticMutation SEXYFINE]] [[BadassMustache 'stache]] came about because a bored animator snuck it in.

** Humberto Velez, Homer's original Latin Spanish voice actor, came up with the dub's translation of the "Sweet Merciful Crap!" line in "Summer of 4 Ft. 2", being "Me quiero volver chango", a phrase a friend would often say.

* In ''WesternAnimation/BatmanTheAnimatedSeries'', [[https://www.youtube.com/watch?v=Ni1EaVcO_1M#t=02m42s The Joker's squee]] after explaining his plan to Batman in the episode Joker's Wild wasn't in the script. Creator/MarkHamill just sort of did it after reading his line, and the cast and crew were laughing so hard that they apparently took the rest of the day off. The next day, they went ahead and added an extra second of animation to include it.

* In ''WesternAnimation/StarTrekLowerDecks,'' Tawny Newsome threw in the line "MOVE, JENNIFER!" to a scene where Mariner was pushing past people. She wasn't privy to the animation, though, which is why [[NamedFromAnotherSpecies there's canonically an Andorian named "Jennifer"]] in the crew.

* The first Greek AlternativeForeignThemeSong of ''WesternAnimation/InspectorGadget'' was [[https://www.retrojunk.com/content/child/intro/page/3972/inspector-gadget/2#/content/child/intro/8136/show this]]. Towards the end, you can hear some of the vocalists bursting into laughter and ad-libbing.

* In the ''WesternAnimation/YoungJustice'' episode "War", Robin and Impulse's fistbump was thrown in by the storyboard artist, who was a fan of [[MythologyGag their friendship in the comics]].

** For an out-of-universe(?) example comes Fry's "No, I'm doesn't" from "The Route of All Evil" in response to being told that alcohol makes one stupid. The line was intended to be "No, it doesn't", but Creator/BillyWest's flub was so hilarious and fitting they kept it.
*** Not quite. The line was written as "No, I'm doesn't", but was intended to be sponen normally. Billy West was confused by the grammar, creating the famous stammered delivery.

* ''WesternAnimation/LooneyTunes''. Creator/BobClampett's 1943 short ''WesternAnimation/AnItchInTime'' has a scene of a dog, having been irritated by a flea, scooting wildly around a carpet on its rear end. As an "inside" joke, Clampett and his animators added an off-color gag of the dog pausing to tell the audience, [[ADateWithRosiePalms "Hey, I'd better cut this out, I may get to like it!"]] fully expecting that either the studio or the [[UsefulNotes/TheHaysCode Hays Office]] would have it removed. Astonishingly, [[{{surprisingly lenient censor}} they didn't.]]

* ''WesternAnimation/LooneyTunes''. Creator/BobClampett's 1943 short ''WesternAnimation/AnItchInTime'' has a scene of a dog, having been irritated by a flea, scooting wildly around a carpet on its rear end. As an "inside" joke, Clampett and his animators added an off-color gag of the dog pausing to tell the audience, [[ADateWithRosiePalms "Hey, I'd better cut this out, I may get to like it!"]] fully expecting that either the studio or the [[UsefulNotes/TheHaysCode Hays Office]] would have it removed. Astonishingly, [[GettingCrapPastTheRadar they didn't.]]

** Recurring guest star Creator/AlbertBrooks is known for doing this. Noticeable when he plays Hank Scorpio in "You Move Only Twice' - most of his fast, random declarations are improvised. The entire Hammock district routine is improvised - hence why Homer only replies with a quick "Yes" because even Creator/DanCastellaneta had trouble keeping up with Brooks. Only at the end does he catch up and reply "Oh, in the hammock district".
** The creators accidentally [[OneSteveLimit gave two characters the last name "Wiggum:"]] the town's [[PoliceAreUseless idiotic police chief]] and one of Lisa's [[TheDitz unintelligent classmates]]. Actually, they're both dumb and kind of chubby... okay, they're father and son now.

* Megatron's famous "''[[VerbalTic yeeeeeeeessss...]]''" from ''WesternAnimation/BeastWars'' wasn't originally scripted, but was improvised by voice actor Creator/DavidKaye, who thought it fit the character. It did, and quickly became his CatchPhrase.

** The first episode contains the line 'Invader's blood marches through my veins - like giant, radioactive rubber pants! The pants command me! DO NOT IGNORE MY VEINS!" The line was supposed to say 'ants'. But it's the kind of show where "pants" actually fits ''better.''
** The episode "Walk of Doom" has a shot where a police officer walks past the camera. He was drawn a little too big on the first take, so they sent it back to be redone... only for the new take to have him become even bigger. At that point, they just accepted it and added booming sound effects to enhance the effect.
** The Hamstergeddon episode involved Ultra Peepi swaggering down the street, not by intention. It came back from animation that way, and Jhonen loved it and had the composer make funk music to go under it. "I want to hear Music/BarryWhite saying 'Ultra Peepi'." Check it out [[https://www.youtube.com/watch?v=1g2tdqomE0M here]]
** In the original script for the scene in "Mortos der Soulstealer", where Zim and Dib yell at each other across an intersection, the street between the two was supposed to be filled with vehicles driving by, which would contribute to why the two had to yell back and forth, in order to be heard over the traffic. When the animation got back from the studio, the crew was chagrined to find that the animators had forgotten to put in the traffic....however, upon reviewing the footage with the dialogue, they found that the awkwardness of the two shouting over nonexistent traffic was hilarious, and kept it as it was.

* [[WordOfGod According to]] Creator/BruceTimm, Terry's revelation as [[spoiler: Bruce's biological son]] in ''WesternAnimation/BatmanBeyond'' and the ''WesternAnimation/JusticeLeagueUnlimited'' episode "Epilogue" stemmed from the earlier realization that, [[spoiler: with his established redhead and light-brunette parents]], Terry and his younger brother's black hair was genetically implausible. Apparently, [[WeWillNotUseStageMakeupInTheFuture We Will Not Use Hair Dye In The Future]].
** In "Injustice For All", a ''Justice League'' episode, Grundy carries off Cheetah, and it was supposed to be implied that he murdered her... Only she was [[{{Blooper}} being carried to jail along with the other members of the Injustice Gang]]. From that, they just said that she was alive, and she appeared in ''Unlimited''.
* [[DarkActionGirl Shego]] from ''WesternAnimation/KimPossible'' was originally created as a generic, boring [[TheDragon Dragon]] to [[HarmlessVillain Dr. Drakken]], but after the creators heard Creator/NicoleSullivan's performance as Shego they gave her a bigger role, making her [[DeadpanSnarker sarcastic]], [[HypercompetentSidekick more competent]] and far savvier than [[GeneralFailure Drakken]]. Today, [[EnsembleDarkhorse she's]] one of the show's most iconic characters.

-->'''Jeepers:''' Hehehehehe... You want to see something strange and mystical?\\
'''Freakazoid: NO!''' Get out of here with that watch! Lay off the poor beavers, will ya?! SHEEEEESH! You're a creep! Go away! We were having a good time until you showed up, Jeepers! '''Urrrg!''' Go have some coffee with cream or something! Because I'll tell you something... This is a happy place!
** According to the audio commentaries, this happened ''a lot''. Even the casting of writer Paul Rugg as Freakazoid was an accident; he was just supposed to be the placeholder, but ended up being so funny (in part because of his wild improvisational skills), that he was cast permanently. Apparently, several large sections of the first episode were entirely made up on the spot by Rugg.
* ''WesternAnimation/LooneyTunes''. Creator/BobClampett's 1943 short ''WesternAnimation/AnItchInTime'' has a scene of a dog, having been irritated by a flea, scooting wildly around a carpet on its rear end. As an "inside" joke, Clampett and his animators added an off-color gag of the dog pausing to tell the audience, "Hey, I'd better cut this out, I [[ADateWithRosiePalms may get to like it!]]", fully expecting that either the studio or the [[UsefulNotes/TheHaysCode Hays Office]] would have it removed. Astonishingly, [[GettingCrapPastTheRadar they didn't]].

** Happens in-universe in ''WesternAnimation/PorkysDuckHunt'', the cartoon which spawned WesternAnimation/DaffyDuck. (In a real-life example, the duck was never intended to be anything more than a one-off gag, and [[AscendedExtra he was retroactively named "Daffy" when he proved to be extremely popular]]).

** A meta example occurred with Bugs Bunny during his redesigning for "A Wild Hare." A friend of Mel Blanc saw a drawing of Bugs Bunny, and said "Tough little stinker, ain't he?" This inspired Mel Blanc to give Bugs Bunny a Brooklyn/Bronx accent.

* The episode "Shrabster" of ''WesternAnimation/{{Sealab 2021}}'' involves an [[LargeHam hammy, over the top]] announcer declaring "Indeed!" along with a linking remark with each scene change. The hammyness ultimately becomes too much for the announcer when leaving a clip involving [[BlackComedy a starving 14 year old African boy]].
-->'''Announcer:''' Dead African child indee-hee-hee-hee-heed... ''(uncontainable laughter)'', I'm sorry. It's just so f-[[SoundEffectBleep bleep]]-ing awful.

** In the first episode, a pony in the background was given crossed eyes as a joke by an animator, and wasn't intended to be visible. Last minute changes moved a bunch of other characters out of the way, making this pony visible. Fans noticed, and were amused, leading to the pony being nicknamed "Derpy Hooves." The joke became so famous that the show's creator, Creator/LaurenFaust, said [[AscendedFanon "she can be Derpy if everyone likes."]] They also gave her the cross-eyed look in most other episodes she appeared in during season 1, and from season 2 on her appearances are fully scripted. She has since gone on to become one of the most beloved characters in the series and something of a mascot for the fanbase, with the [[http://www.derpibooru.org largest MLP image booru]] on the net being named after her.

* A rather unhumourous example happened in ''WesternAnimation/RenAndStimpyAdultPartyCartoon'' spinoff that ultimately led to cancellation of the series. The episode "Onward and Upward" contained a graphic homosexual sex scene between the eponymous duo in the original run, added as a joke by an animator. Creator Creator/JohnKricfalusi explained that there was never supposed to be any actual sex in it, that Ren and Stimpy were supposed to be playing baseball under the sheets (as a part of a vague "pitcher and catcher" metaphor earlier in the episode). He claimed he wanted to cut it straight away, but he felt sorry for the animator who thought it was funny. The scene was left in and caused a minor uproar at an animation newsgroup, where a group of people [[TooDumbToLive thought Kricfalusi was trying to sabotage his own show]] - the executives at Creator/SpikeTV saw this conversation, thought that's the way everyone felt and cancelled the project. Go figure.

* The //WesternAnimation/DextersLaboratory// episode "Chubby Cheese" has a sequence where the characters watch a performance by an animatronic band in the titular SuckECheeses establishment - at the very end of the scene, some audience members inexplicably fly off into the distance. This was an animation mistake that has had two explanations: One is that the animation department misinterpreted a storyboard where the audience all had their arms in the air as a superhero pose rather than cheering; the other is that they misunderstood a stage direction about the audience "taking off", as in leaving. Regardless, this got left in the final product with an appropriate sound effect added - it added to what was already a pretty surreal scene.

* Reportedly, during the first table reading for ''WesternAnimation/ScoobyDooWhereAreYou'', Velma's voice actress Nicole Jaffe dropped her glasses and exclaimed, "[[BlindWithoutEm My glasses! I can't see without my glasses!]]" The writers liked the line so much, and thought it was so in-character for Velma, that they turned it into a RunningGag[=/=]CatchPhrase for her. (Curiously, she didn't say that in the first episode. After Scooby knocks her down and her glasses come off, she says "Now look what that dog did. He knows I can't see without my glasses!")
* In the ''WesternAnimation/YoungJustice'' episode "War," Robin and Impulse's fistbump was thrown in by the storyboard artist, who was a fan of [[MythologyGag their friendship in the comics]].

* In the original animation of ''{{WesterAnimation/Tigtone}}'': Tigtone's voice actor Nils Frykdal described a side quest to obtain magic boots as "Treasureful" instead of "Treacherous", which fit the character so perfectly it was kept in the final cut.
* The WesternAnimation/DextersLaboratory episode "Chubby Cheese" has a sequence where the characters watch a performance by an animatronic band in the titular SuckECheeses establishment - at the very end of the scene, some audience members inexplicably fly off into the distance. This was an animation mistake that has had two explanations - one is that the animation department misinterpreted a storyboard where the audience all had their arms in the air as a superhero pose rather than cheering, the other is that they misunderstood a stage direction about the audience "taking off", as in leaving. Regardless, this got left in the final product with an appropriate sound effect added - it added to what was already a pretty surreal scene.

* Reportedly, during the first table reading for ''WesternAnimation/ScoobyDooWhereAreYou'', Velma's voice actress Nicole Jaffe dropped her glasses and exclaimed, "[[BlindWithoutEm My glasses! I can't see without my glasses!]]" The writers liked the line so much, and thought it was so in-character for Velma, that they turned it into a RunningGag[=/=]CatchPhrase for her.(Curiously, she didn't say that in the first episode. After Scooby knocks her down and her glasses come off, she says "Now look what that dog did. He knows I can't see without my glasses!")

* Reportedly, during the first table reading for ''WesternAnimation/ScoobyDooWhereAreYou'', Velma's voice actress Nicole Jaffe dropped her glasses and exclaimed, "[[BlindWithoutEm My glasses! I can't see without my glasses!]]" The writers liked the line so much, and thought it was so in-character for Velma, that they turned it into a RunningGag[=/=]CatchPhrase for her.

* Creator/CraigGerber has mentioned that some of the dialogue on ''WesternAnimation/ElenaOfAvalor'' wasn't in the scripts and is improvised by VAs. In particular, much of King Hector's dialogue was improvised by Creator/JessHarnell due to still fitting his boisterous nature.

* Creator/CraigGerber has mentioned that some of the dialogue on ''WesternAnimation/ElenaOfAvalor'' . In particular, much of King Hector's dialogue was improvised by Creator/JessHarnell due to still fitting his boisterous nature.

* [[WordOfGod According to]] Creator/BruceTimm, Terry's revelation as [[spoiler: Bruce's biological son]] in ''WesternAnimation/BatmanBeyond'' and the ''WesternAnimation/JusticeLeagueUnlimited'' episode "Epilogue" stemmed from the earlier realization that, [[spoiler: with his established redhead and light-brunette parents]], Terry's black hair was genetically implausible. Apparently, [[WeWillNotUseStageMakeupInTheFuture We Will Not Use Hair Dye In The Future]].

* The original script for ''[[Disney/TheManyAdventuresOfWinnieThePooh Winnie the Pooh and Tigger Too]]'' had Tigger simply saying, "Goodbye". But Creator/PaulWinchell's third wife, Jean Freeman, suggested he ad lib it to "T.T.F.N. Ta ta for now," which soon became an iconic catchphrase for Tigger.

** In "Coldhearted," we briefly see two policemen talking. One of them was supposed to be a woman, but the art came back with two men. Creator/CreeSummers had already recorded the line for one, so they just altered the pitch [[CrossdressingVoices and used it anyway]].

** In the original version of the episode, when Iron Man got Thor's powers, he would be seen carrying the hammer, but when Dan and Swampy asked the execs at Marvel about this, they told them that "wielding Mjolnir was about worthiness not power", but then asked about flying and lightning, and they told them it only worked with the hammer. So they put the whole conversation in the show between Iron Man and Thor.
* Two episodes of ''WesternAnimation/RickAndMorty'' ("Rixty Minutes" and "Interdimensional Cable II") revolve around Rick and Morty watching interdimensional TV. The scripts for the actual TV segments are largely improvised, and a lot of awkward deliveries, stumbling over words or just [[{{Corpsing}} cracking up at the end of a scene]] are left in ([[RuleOfFunny presumably because they're funnier that way.]]) This is quickly lampshaded when Rick & Morty point out how improvisational interdimensional TV feels.

** [[BadassBookworm Sokka]] was originally intended as a more sullen character. However, his voice actor, Jack DeSena, was a Creator/JimCarrey-inspired comedian, so Sokka gradually turned into a much more over-the-top comic relief. The creators noted that because of this change, [[LittleMissBadass Toph]] ended up filling Sokka's original role.