History ThrowItIn / WesternAnimation

* In the ''CodeLyoko'' episode "Tidal Wave", Odd's final line, "I'm so ''hungryyyyy''!", was ad-libbed by his dub actor.

** Happens in-universe in ''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]]).

* In ''WesternAnimation/MyLittlePonyFriendshipIsMagic'', 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, Lauren Faust, 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 post-production in season 1. In season 2, her appearances are now fully scripted.

* ''HomeMovies'' is so improvised, you can hear the actors stuttering and trying to come up with a new line.

* In the ''CodeLyoko'' episode "Tidal Wave", Odd's final line, "I'm so hungry!", was ad-libbed by his dub actor.

* A rather unhumourous example happened in ''TheRenAndStimpyShow Adult Party Cartoon'' 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 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 SpikeTV saw this conversation, thought that's the way everyone felt and cancelled the project. Go figure.

* ''WesternAnimation/LooneyTunes''. BobClampett's 1943 short ''An Itch in Time'' 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]].

* For the ''WesternAnimation/{{Madagascar}}'' franchise, Creator/DreamWorks animator Tom [=McGrath=] recorded a temporary vocal track for Skipper the penguin which was meant to be overdubbed by Robert Stack, but Stack died as the movie was finishing production. According to [[http://www.moviefreak.com/features/interviews/tommcgrath.htm McGrath himself]], co-creator Eric Darnell just told [=McGrath=] to leave his own vocal track in, as he thought it sounded good.

** The genetics of hair color is not well understood the only color they really understand is redheads because that hair color falls outside the blonde to black spectrum. You could probably find a pair of brothers with black hair whose parents are a red head and a brunette.

** 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 Creator/DanCastellaneta had trouble keeping up with Brooks. Only at the end does he catch up and reply "Oh in the hammock district".

* [[DarkActionGirl Shego]] from ''KimPossible'' was originally created as a generic, boring [[TheDragon Dragon]] to [[HarmlessVillain Dr. Drakken]], but after the creators heard Nicole Sullivan's performance as Shego they gave her a bigger role, making her [[DeadpanSnarker sarcastic]], [[HypercompetentSidekick more competent]] and [[DangerouslyGenreSavvy far savvier]] than [[GeneralFailure Drakken]].

* For the ''{{Madagascar}}'' franchise, Creator/DreamWorks animator Tom [=McGrath=] recorded a temporary vocal track for Skipper the penguin which was meant to be overdubbed by Robert Stack, but Stack died as the movie was finishing production. According to [[http://www.moviefreak.com/features/interviews/tommcgrath.htm McGrath himself]], co-creator Eric Darnell just told [=McGrath=] to leave his own vocal track in, as he thought it sounded good.

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

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

* While ''WesternAnimation/PhineasAndFerb'' contains very few animations, 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.

* On ''WesternAnimation/TheSimpsons'', the often-quoted sung line: "I am so smart! I am so smart! S-M-R-T! I mean, S-M-A-R-T!" This was an actual mistake by voice actor DanCastellaneta, but it was just so "Homer" they left it in.

** 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 DanCastellaneta had trouble keeping up with Brooks. Only at the end does he catch up and reply "Oh in the hammock district".

* The WoodyWoodpecker short ''Wet Blanket Policy'' originally didn't have "The Woody Woodpecker Song" in it, but it was added in at the last minute by WalterLantz, when he discovered how much of a surprise hit the single had become.

** 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 DanCastellaneta had trouble keeping up with Brooks. Only at the end does he catch up and reply "Oh in the hammock district".

** Recurring guest star 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 Dan Castellaneta had trouble keeping up with Brooks. Only at the end does he catch up and reply "Oh in the hammock district".

* In ''WesternAnimation/BatmanTheAnimatedSeries'', 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.

* ''WesternAnimation/LooneyTunes''. BobClampett's 1943 short ''An Itch in Time'' 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 [[HaysCode Hays Office]] would have it removed. Astonishingly, [[GettingCrapPastTheRadar they didn't]].

** [[WesternAnimation/WhatsOperaDoc "SMOOOOOOOOOOOOOOOOGGGGGGGGGG!"]]
** Happens in-universe in ''PorkysDuckHunt'', the cartoon which spawned Daffy Duck. (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]]).

** Recurring guest star AlBrooks 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 Dan Castellaneta had trouble keeping up with Brooks. Only at the end does he catch up and reply "Oh in the hammock district".

** They also gave her the cross-eyed look in most other episodes she appeared in during post-production in season 1. In season 2, her appearances are now fully scripted. Unfortunately, when Derpy made the leap to AscendedFanon, it backfired spectacularly, largely due to people who didn't get the joke.

** They also gave her the cross-eyed look in most other episodes she appeared in during post-production in season 1. In season 2, her appearances are now fully scripted.

** In one episode, when Snake attempts to murder Homer with a trap utilizing piano wire in order to get his car back, the trap missed Homer, but manages to amputate Mr. Van Houten's arm while he was complaining about his sandwich. Originally, the piano wire was simply supposed to cut the sandwich to what he wanted it to be like, but the animators decided to make it a bit more shocking by having it cut off his arm instead.