History ThrowItIn / WesternAnimation

** Similarly in "Grade School Confidential", Homer is using a megaphone to talk to Bart (who was on the roof of the school) to ask him [[SkewedPriorities where their [=TV=] remote is]]. Bart shouts to him to check his pocket, he does and finds the remote and then tells Marge and Lisa who were right next to him that it was in his pocket through the megaphone by mistake. "IT WAS IN MY-(puts megaphone down) It was in my pocket." This was a mistake by Castellaneta while using a real megaphone during recording that he tried to correct but the writers thought it was in character for Homer so they kept it in.
** Homer's famous "D'oh!" was improvised by Castellaneta. The script only said "annoyed grunt." (And still does.) It was originally a Creator/LaurelAndHardy reference (James Finlayson would occasionally let out a pained "D'ooooooooooh"), but Castellaneta was told to shorten it the first time he used it.
** As was Homer's song "Dancing Away My Hunger Pangs" on the season 12 episode "Hungry, Hungry Homer" (where Homer goes on a hunger strike to save the town's baseball team).
** Recurring guest star Creator/AlbertBrooks is known for doing this. Noticeable when he plays Hank Scorpio in "You Only Move 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"]]. Specifically, Clancy, the town's [[PoliceAreUseless idiotic police chief]], and Ralph, Lisa's [[TheDitz unintelligent classmate.]] They then realized that both characters are dumb and kind of chubby and decided to make them father and son.
** Creator/HumbertoVelez, 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". It was translated as "Me quiero volver chango" ("I want to go back to being a monkey"), a phrase his friend would often say.
* ''WesternAnimation/AdventureTime'': When Adam Muto pitched the episode "What Was Missing", he had misspoken, which is the reason why Finn says, "I'll get your kid back toy". The team thought it was funny and kept the flub for the actual episode.

** Megatron's famous "''[[VerbalTic Yeeeeeeeessss...]]''" 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.
** David also coughed while recording one of Megatron's power-hungry laughters, but they decided to leave it in, with the animators adding a surprised reaction shot of Inferno to complete the effect.
* ''WesternAnimation/{{Futurama}}'': An InUniverse example is where Calculon is showing a clip of a new episode of his show where he does a BigNo. He informs the talk show host he was actually supposed to say "yes" but "gave it a little twist".
** 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 spoken normally, but Creator/BillyWest was confused by the grammar, creating the famous stammered delivery, and it was so fitting that they kept it in.

* ''WesternAnimation/HeyArnold'' has an art example: when somebody accidentally drew a very OffModel version of Arnold, they decided to make him an actual character, Arnold's CountryCousin Arnie, who has two episodes centered around him.
* ''WesternAnimation/InvaderZim''
** 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.
* In ''WesternAnimation/BatmanTheAnimatedSeries'', The Joker's squee after explaining his plan to Batman in the episode "[[Recap/BatmanTheAnimatedSeriesE41JokersWild 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.
* [[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.

* ''WesternAnimation/{{Freakazoid}}'''s voice actor was supposed to refuse a literal plot hook with just a simple "No." The sequence ended up twenty seconds longer because of [[https://www.youtube.com/watch?v=T_rP5SDvyKI him adding a tiny bit more.]]

** Paul Rugg's famous 'Low Bridge' chant was also meant to be a placeholder, but was apparently so utterly perfect and so like Freakazoid that they just kept it in - much to Rugg's chagrin.
* ''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, [[DoesThisRemindYouOfAnything "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, [[SurprisinglyLenientCensor they didn't.]]
** This was apparently par for the course -- [[CensorDecoy they'd include really extreme stuff to distract the Hays Office so the stuff they really wanted in would scoot by, only for the Hays Office to ignore the decoys and go for the real meat anyway.]]

** 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.]]

---> '''Daffy:''' Don't let it worry ya, skipper, I'm just a crazy darn fool duck. ''(bounces away across the pond, laughing maniacally)''
** 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.

** Something the So-and-So's long winded goad over what to do with the ring in "The Battle Royale" was added last minute due to the episode coming in a minute short during production.

* The episode "Shrabster" of ''WesternAnimation/{{Sealab 2021}}'' involves a [[LargeHam hammy, over the top]] announcer declaring "Indeed!" along with a linking remark with each scene change. The hamminess ultimately becomes too much for the announcer when leaving a clip involving [[BlackComedy a starving 14 year old African boy.]]

** [[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.

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

** An in-universe case when the Gaang watches a play about themselves, and Sokka goes up to the actor playing him and suggests a few lines and jokes. The actor prommptly starts incorporating these suggestions into his performance, forcing the other actors to adjust to these unscripted lines on the fly. [[FunnyBackgroundEvent The actor playing Toph is visibly confused the first time he does it]].
* SequelSeries ''WesternAnimation/TheLegendOfKorra'' has a scene in "The Spirit of Competition" where Mako is angrily walking through a door and completely ignores a fan trying to say hi ("Hey Mak''ooooo''-oh"). [[http://2-cents.tumblr.com/post/22891956615/hey-guys-i-made-my-acting-debut-last-week-as-the This originated]] when someone drew a random extra standing next to Mako in the animatic and the episodes director thought he looked disappointed.
** There was an In-Universe case in a mover where Bolin kisses an actress in a scene where he wasn't supposed to and the director decided to keep the kiss.

* In the ''Daniel and the Lions' Den'' segment of the first ''WesternAnimation/VeggieTales'', a render glitch made a sudden flash of light in the background during a scene. The animators weren't able to fix it, so they just added a thunder sound effect and made an instant storm, that actually darkens the mood in the right way.

** 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.
** Lending to its realistically unpracticed and stumbling delivery, the Cloudsdale anthem as performed by Spike in "[[Recap/MyLittlePonyFriendshipIsMagicS4E24EquestriaGames Equestria Games]]" was [[https://twitter.com/CathyWeseluck/status/483786494260166656 genuine improvisation]] on Creator/CathyWeseluck's part.
** In "[[Recap/MyLittlePonyFriendshipIsMagicS4E9PinkieApplePie Pinkie Apple Pie]]", Creator/MichelleCreber was told to improvise a rap song for Apple Bloom when she found the map. She chose to replicate a "Ponylicious" meme, unprompted.
** The episode "[[Recap/MyLittlePonyFriendshipIsMagicS6E14StrangerThanFanFiction Stranger than Fan Fiction]]" featured [[InsufferableGenius Quibble Pants]] [[CreativeClosingCredits giving a monologue over the credits]] about the next ''JustForFun/DaringDo'' book. Creator/PattonOswalt, who voiced the character, improvised the whole thing.

* 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 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.
** For an actual humorous example, the animation error in Stimpy's eyes (he looks like [[WesternAnimation/TheFlintstones Barney Rubble]] for a [[http://img.photobucket.com/albums/v98/speedyboris/renandstimpy/bumper09-300x225_zpsd02505b8.jpg split second]]) in "Stimpy's Breakfast Tips" was so hilarious that John left in in.
* When building the models for the TV series ''WesternAnimation/{{Tugs}}'', it was found that Zorran's eye mechanism caused the front of his hat to tip up. They left it in because they thought it added to the expressiveness of the character.

* According to [[http://scifi.about.com/od/starwarstelevision/a/Star-Wars_Clone-Wars_Interview-With-Ashley-Eckstein.htm Ashley Eckstein]], she was asked to use an Icelandic accent for the voice of Ahsoka Tano in ''WesternAnimation/StarWarsTheCloneWars'', but when she came in with a practiced Icelandic accent, it apparently [[RealityIsUnrealistic wasn't what they expected]]. The voice she ended up getting told to do in the show is based on the tones in her ''real'' voice during the audition when she got frustrated that she couldn't figure out what accent they wanted.

* ''WesternAnimation/HomeMovies'' is so improvised, you can hear the actors stuttering and trying to come up with a new line. The show's creators have noted that some fans were upset to find that the show was even loosely scripted--having plot points outlined, but leaving most dialogue to the actors.
* Nick Bakay and Richard Steven Horvitz, respectively the voice actors for Norbert and Daggett on ''WesternAnimation/TheAngryBeavers'', improvised a lot of their dialogue as well.
* In the first episode of ''WesternAnimation/TheFlintstones'' the script originally called for Fred to yell "Yahoo!" but Alan Reed thought that was too bland and asked if he could come up with something better. This is how he came up with the CatchPhrase "Yabba-dabba-doo!", as a play on the popular slogan "A little dab'll do ya."
* 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!")

** Creator/TomKenny actually had a cold during production of "Suds"; if you listen closely, his recordings sound quite genuine.

* 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 [[NameFromAnotherSpecies there's canonically an Andorian named "Jennifer"]] in the crew.
* In the ''WesternAnimation/YoungJustice2010'' 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]].

* While ''WesternAnimation/PhineasAndFerb'' contains very few ad libs, one notable one appears during the song "Only Trying to Help" from the episode "[[Franchise/MarvelUniverse Phineas and Ferb: Mission Marvel]]". The end of the song, where Isabella and Candace repeat a line of the chorus, was originally improvised by Isabella's voice actress, Alyson Stoner.
** 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.

* ''WesternAnimation/TheLoudHouse''' has two examples:
** The titular family owes their name to this trope. Creator/ChrisSavino was exchanging emails with a friend who was helping him work out some of the kinks and the friend asked if "Loud" was the family's surname; Savino replied "It is now!"
** In the episode "Back Out There", Creator/VanessaMarshall , who voiced an old woman named Tina and the waitress, also voiced a young girl named in the script as "young flustered girl" upon seeing the boys. She then started hiccupping during recording, which was then integrated into the episode due to still filling the same role, and the character was credited as "young hiccupping girl" .

* In the original animation of ''WesternAnimation/{{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 that 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.
* The original script for ''[[WesternAnimation/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 the ''WesternAnimation/SouthPark'' episode "South Park is Gay!," the [[spoiler:Crab People]] were originally just a placeholder Creator/TreyParkerAndMattStone were using until they figured out the ''actual'' plot for act three, but then just ran with it when they couldn't come up with anything else. For what it's worth, later episodes have used "[[spoiler:Crab People]]" as a stand-in for [[SelfDeprecation a really stupid idea]].
** InUniverse example: In "A Very Crappy Christmas," the boys are making a Christmas film. It was originally supposed to be wholesome, but naturally, [[HotBlooded Kyle]] and [[PoliticallyIncorrectVillain Cartman]] got into a fight while recording and started screaming profanity at each other.

* According to ''WesternAnimation/WeBareBears'' creator Daniel Chong, Demitri Martin, Ice Bear's voice actor, normally records lines by himself. As a result, this gives Martin a lot of freedom to ad-lib.
* Creator/CraigGerber has mentioned that some of the dialogue on ''WesternAnimation/ElenaOfAvalor'' wasn't in the scripts and is improvised by voice actors. In particular, much of King Hector's dialogue was improvised by Creator/JessHarnell due to still fitting his boisterous nature.
* The first Greek AlternativeForeignThemeSong of ''WesternAnimation/InspectorGadget'' was [[https://bbcdn.stablecube.com/file/rj-intro-videos/2NQ8tj7yKn15ad7oX261n.mp4 this]]. Towards the end, you can hear some of the vocalists bursting into laughter and ad-libbing. This was left in the final recording.
* WesternAnimation/TwelveOunceMouse: The character Rhoda was first sketched on the back of a ''WesternAnimation/PerfectHairForever'' script, and several lines of dialog could be seen inside him/her. The makers liked the look and kept it in the show.

** In "House Sittin' for Sandy", [=SpongeBob=] spends the whole first half of the episode in Sandy's treedome without a water helmet, until Patrick arrives and reminds him he needs one. This was because halfway into production, the crew discovered they forgot to put a helmet on [=SpongeBob=]; rather than start over, they kept it in, and Patrick was added to the episode to give [=SpongeBob=] the helmet.