History ThrowItIn / WesternAnimation

** 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 Creator/DanCastellaneta, but it was just so "Homer" they left it in.

** 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, and the character was credited as "young hiccupping girl" .

** [[BadassBookworm Sokka]] was originally intended as a more sullen character. However, his voice actor 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.

* ''WesternAnimation/TheLoudHouse'''s 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!"

* 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.

* ''WesternAnimation/TheLoudHouse'''s titular family owes their name to this trope. 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!"

** 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=b7vnD5WQjsA here]].

** 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 [[AdLibbing wild improv]]), that he was cast permanently. Apparently, several large sections of the first episode were entirely made up on the spot by Rugg.

* ''WesternAnimation/{{Freakazoid}}'''s voice actor was supposed to refuse a plot hook with a "No," and the sequence ended up twenty seconds longer because of [[https://www.youtube.com/watch?v=T_rP5SDvyKI what he did say.]]

** 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 improv), that he was cast permanently. Apparently, several large sections of the first episode were entirely made up on the spot by Rugg.

* 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.

** 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".

* In the first episode of ''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."

* In the first episode of ''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!"

* When building the models for the TV series ''{{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.

** [[BadassBookworm Sokka]] was originally intended as a more sullen character. However, his voice actor was a 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.

* A rather unhumourous example happened in ''WesternAnimation/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 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.

* ''WesternAnimation/LooneyTunes''. Creator/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]].

* [[WordOfGod According to]] 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]].

** Homer's famous "D'oh!" was improvised by Castellaneta. The script only said "annoyed grunt". (And still does.)

* 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 points out how improvisational interdimensional TV feels.

* 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 line reading]] are left in ([[RuleOfFunny presumably because they're funnier that way.]]) This is quickly lampshaded when Rick & Morty points out how improvisational interdimensional TV feels.

* In the episode "Rixty Minutes" of ''WesternAnimation/RickAndMorty'', Rick and Morty are watching interdimensional TV. A trailer for a movie called "Two Brothers" plays, and the trailer's narrator (Justin Roiland, who also voices Rick and Morty) starts laughing at the end over how goofy the idea is and they decided to leave it in. In the same episode, during an episode of "Raising Gazorpazorpfield", a fictional parody of Garfield, Gazorpazorpfield (also voiced by Roiland) is insulting John, and Roiland again laughs while saying the word "enchalatas".