For the Roland and Rattfink cartoon "The Foul Kin", writer Sid Marcus recycled the plot from a Woody Woodpecker cartoon he directed years earlier, "Skinfolks".
Many of the early Hanna-Barbera series reused stories from old Tom and Jerry cartoons (understandable, since the studio was made up of former MGM artists), as well as a few Looney Tunes (some of the Warners story men wrote for HB). For example, the T&J short "Pecos Pest", about a relative of Jerry's from Texas who comes to practice for a TV appearance and uses Tom's whiskers as guitar strings, was redone as a Pixie and Dixie short. Similarly, the Bugs Bunny cartoon "Windblown Hare", in which the Three Little Pigs sell Bugs their homes just as the Big Bad Wolf arrives, was redone with Yogi Bear.
Cartoon writer David Wise (no relation to the video game composer) did this a lot:
Wise also recycled huge chunks of his script for the Transformers episode "Microbots" for the TMNT episode "Shredder and Splintered". In the former, the Autobots shrink themselves to go inside Megatron's body, in the latter, the turtles climb inside the Kaiju-sized Krang, and from that point on the two episodes feature virtually identical dialogue and action.
Especially glaring is the TMNT episode "Poor Little Rich Turtle", which is almost beat-for-beat identical to the Transformers episode "The Girl Who Loved Powerglide".
The episode "Sonic is Running" and The Adventures of Super Mario Bros. 3 episode "Princess Toadstool For President" (both DiC Entertainment cartoons produced around the same time) both involve one of the main characters running for president against the Big Bad of the series. In the end, the hero wins in a landslide victory, and it's revealed that the villainous character received only one vote (his own) because even his two flunkies voted against him.
Another example of an AoStH episode with a similar plot to a Mario cartoon episode is the episode "Tails in Charge" to the The Super Mario Bros. Super Show! episode "Quest For Pizza". Both episodes center around the secondary protagonist (Tails, Luigi), as the main protagonist is knocked out or becomes unresponsive because of the villains' weapons (Sonic gets turned to stone by Robotnik's Super Supreme Stopper Zapper, Mario gets bitten by a poisonous snake). The objective of both episodes is for the secondary protagonist to keep their friend safe until they can cure them, and both episodes involve the antagonist setting up traps to capture the secondary protagonist, only for them to backfire on them completely.
Yet another AoStH episode with a recycled script was "Over the Hill Hero", which is very similar to the Teenage Mutant Ninja Turtles (1987) episode "Superhero for a Day". Both episodes feature a former Golden Age superhero (Captain Rescue and Gadget Man) coming out of retirement to try and help out the main characters (Sonic and the Turtles) against the main villain (Robotnik and Shredder), but end up only makings things worse for the heroes, leading to the main characters getting captured and leading to the Golden Age heroes feeling guilt-ridden as a result and watching old tapes of their glory days and then redeeming themselves by rescuing the main characters and helping them defeat the bad guys. Both episodes even featured the same writer, Francis Moss.
The Alvin and the Chipmunks episode "The Brunch Club" and the Teen Titans Go! episode "Hey You, Don't Forget About Me In Your Memory" both spoof The Breakfast Club, have the characters get in trouble for something they did by accident and wondering what they could have done to prevent it from happening, and replace Simple Minds' "Don't You (Forget About Me)" with an original song unlike most homages to the film. ("What Were You Doing At The Time?" for Alvin and "Crane Kick" for Titans).
On the subject of Teen Titans Go!, the episode "Oh Yeah!" has the same plot as the Animaniacs episode "Fake", in which one of the characters convinces their friend that wrestling is fake, but the friends do not believe what they are saying.
"Master Detective", which is similar to the U.S. Acres short "How Now, Stolen Cow?", in which the main character solves a mystery involving missing farm animals.
The plot of the episode "Accept the Next Proposition You Hear" is similar to another U.S. Acres short, "Fortune Kooky", in which a character thinks that what fortune cookies say can happen in real life.
"No Power" has a similar plot to one of the Garfield shorts on the same show, "Five Minute Warning". In both, the characters have to go a certain period of time without doing something they like in order to get a reward.
"Obinray" and the U.S. Acres segment "Double Trouble Talk" have the main characters learn a secret method of talking in order to avoid something they despise from occuring (eavesdropping in the former and doing chores in the latter).
The episode "40%, 40%, 20%" is similar to the Arthur episode "Play It Again, D.W.", in which the main characters are tired of hearing someone play their favorite song over and over and don't understand why the character who loves the song is obsessed with it, only to have the character with the obsession lose the item which contained their favorite song.
"Fish Water" is similar to the Magic Adventures of Mumfie episode "A Fishy Tale", in which a character wants to free their pet fish they won from a carnival into the ocean when it feels sad.
"BL4Z3" is similar to the infamous Pokemon episode "Electric Soldier Porygon", in that both involve the characters being transported inside of a computer to stop a problem being placed in the system by an enemy (in the Teen Titans Go episode, Robin tries to stop someone from pirating stuff, while in the Pokémon story, the characters try to stop Team Rocket from putting a virus into the Pokémon Center's computer system.)
"Artful Dodgers" borrows its plot from Space Jam, in which the protagonists have to battle villains in a sports tournament.
"Whodundidit?" is similar in plot to "Sleuth or Consequences" from The Loud House. In both, the characters try to find out who clogged the toilet.
In some cases, Teen Titans Go! recycles their own plots from earlier episodes:
"Puppets, Whaaat?", "Halloween" and "And The Award For Sound Design Goes To Rob" all use the plot of "one of the Titans makes a deal with a supernatural being to change something about their world, but it goes wrong".
The worst offender of this is the "TV Knight" series of episodes, which all use the same plot of being A Day in the Limelight episodes about Batman and Commissioner Gorden hanging out and watching TV.
"Butt Atoms" is similar to "Waffles", in which Robin gets annoyed that his friends are doing something he doesn't like and tells them to stop doing it (in the former, they won't stop farting and telling jokes about it, while in the latter, Beast Boy and Cyborg will not stop saying "waffles"), but they don't listen.
"Grube's Fairytales", "Orangins" and "Don't Be An Icarus" all use the plot of the Titans giving their own takes on famous stories.
The plot of "Career Day" would later be recycled into an episode of Unikitty! with the same name.
Speaking of Alvin and the Chipmunks, "Home Sweet Home" shares parallels with "My Pharoah Lady" in which Alvin and Brittany maintain their race for Carnival Monarch by betting Ricky and Missy Snootson (respectively) that Michael Jackson will be visiting the kids' school and King Rutintootin exists. Unlike "Pharoah Lady" (where Brittany drops out of the race for Carnival Queen), Alvin's fate for Carnival King at the end of "Home Sweet Home" was not shown.
Archer: Season six's "Nellis" is identical to season four's "Midnight Ron". Archer is stranded in a distant city (Montreal in "Midnight Ron, Las Vegas in "Nellis") after losing all his money at a casino and has difficulties returning home due to legal troubles (drunkenly burning his passport in "Midnight Ron", being on a No Fly List and the train equivalent in "Nellis") and someone from the office must personally get him (his step-father Ron drives to Montreal in "Midnight Ron", Cheryl, Pam, Cyril, Ray and Krieger fly out in Cheryl's personal jet in "Nellis"), their vehicle is too damaged to use further following an attack (Ron's Cadillac is run off the road by mobsters trying to rob him in "Midnight Ron", Cheryl's jet is hit by a surface-to-air missile while flying too close to Area 51 and must crash-land at Nellis AFB in "Nellis"), Archer must bluff his way out of a situation (using his pistol as a Weapon for Intimidation, first against "tranny bikers" and then two hobos with switchblades in "Midnight Ron", pretending to be CIA agent Slater and threatening a Colonel with being subjected to Project MK ULTRA in "Nellis") and ultimately Archer and companions must acquire an alternate means of transport to get home (hopping on a freight train before getting a replacement Cadillac from one of Ron's dealerships in "Midnight Ron", stealing a C-130 Hercules in "Nellis"). It even has a minor scene at the beginning of Archer being accosted by someone while using a payphone to call the office.
The first wish is used by a member of the group for "some excitement", leading to a fight against some Mooks and introduction of the genie-like character.
The group debates on how to use the second wish, until it is used for The Ditz to be smarter, by accident.
The last wish is used for a way to destroy the genie, but fails due to a rule which forbids the genie from being harmed. Thus, the wish is wasted.
The genie is set free and is revealed to be a Sealed Evil in a Can. As they begin to wreak havoc, The Ditz seemingly betrays the group and switch sides. When allowed an extra wish, it's used to not only return the group to the point before they found the item that summoned the genie, but to ensure they never discover it in the first place.
The group returns to the start of the episode, where the character who wished for excitement is stopped before they did it again, leaving the genie trapped.
The Season 5 episode "The World Record" has almost the same plot as the Hey Arnold! episode "World Records" (made three years earlier). In both episodes, the main characters try to break a world record until they settle down on making the world's largest pizza, with the only difference being that Arthur's attempt is successful while Arnold's fails. Both episodes also have a character unsuccessfully trying to break the record for walking backwards. The puppet show Under the Umbrella Tree (which predates both cartoons) also has a similar episode, "Jacob's World Record," which also includes an attempt to break the record for walking backwards, although it doesn't include pizza-making. The Lizzie McGuire episode "Come Fly With Me" also had characters (Matt and Lanny) attempting numerous world records before ultimately getting the record for "most attempts at breaking a world record" (like Jacob in Umbrella Tree and Arnold and the kids did), though it was relegated to a subplot.
The Casagrandes has yet another episode- "For the Record" with a plot where a character(Samir) tries repeatedly to break a world record only to fail but in the end ends up getting the record for "most failed attempts to get a record".
"DW and Bud's Higher Purpose" has the same plot as the SpongeBob SquarePants episode "Roller Cowards", in which two friends attempt to ride a rollercoaster but must overcome a specific problem; they are either too afraid or too short.
"Buster the Lounge Lizard" has a strikingly similar plot to the Recess episode "Teacher's Lounge" as both episodes center around the kids fantasizing about what the teacher's lounge is really like and then trying to sneak inside.
Episodes "Gamma World" and "Code Red" both have a villain using a fictional brand of science to disfigure crowds of people (Hulk villain the Leader in the former, Captain America villain Red Skull in the latter), Captain America, The Wasp, and Black Panther becoming disfigured, at least one Avenger having the antidote (created by another crimefighter) shot into himself or herself, and Thor evading a transformation before engaging in a side battle with a gamma-powered monster.
"Powerless!" has some plot elements blatantly copied from Thor's movie. Namely, Thor becomes a mortal, Loki tries to kill him with Destroyer armor, Thor sacrifices himself to protect mortal companions from the Destroyer, and Thor regains his hammer and his immortality as rewards for his selflessness.
Baby Looney Tunes seems to have recycled plots from other cartoons where infants are the main characters. "Like A Duck to Water" is similar to the Muppet Babies (1984) episode, "Beach Blanket Babies", wherein one of the characters is afraid to go swimming for the first time (Baby Daffy in the former, Baby Fozzie in the latter), while "Leader of the Pack" essentially uses the same plot as the Rugrats episode, "Tommy and the Secret Club", wherein one of the characters starts their own secret club and makes their friends do certain tasks for them in order to join (Baby Daffy in the former, Angelica in the latter).
Both the Rugrats episode "Kid TV" and the Baby Looney Tunes episode "I Strain" use the same basic plot as the Muppet Babies (1984) episode "I Want My Muppet TV". In all three episodes, the television breaks, so the babies make their own TV out of a cardboard box and act out their own TV shows with it.
Both the Baby Looney Tunes episode, "The Dolly Vanishes" and the Muppet Babies (2018) episode, "Mystery on the Muppet Express" use the same basic plot as the Rugrats episode, "Murmur on the Ornery Express". In all three episodes, the favorite toy of one of the babies goes missing during a train ride (Edna, Buddy, and Wawa, respectively), and the other babies search the train for it. The Madeline episode "Madeline on the Orient Express" has much the same plot too, albiet with a snake charmer's missing snake instead of a missing toy. Of course all of these episodes are Lighter and SofterWhole Plot References to Murder on the Orient Express.
The classic Beany and Cecil short Beany And Cecil meets The Invisible Man is a recycled plot to The Edgar Bergen Cartoon Show (one of Bob Clampett's lost work).
Bravestarr has two episodes, "No Drums, No Trumpets" and "To Walk a Mile", that have the same plot: "a former Galactic Marshal, who has sworn off guns due to a tragic incident in his past, is looked down upon by his child. Then, said child is kidnapped by bad guys, forcing him to take up his weapon once more." Alan Oppenheimer even voiced the former Marshal character in both episodes.
Blue's Clues & You! is an example of a whole series using this trope, as it is comprised of shot-for-shot remakes of Blue's Clues episodes. For example, "Sad Day with Blue" is a recreation of "Blue's Sad Day" - both being about Blue being sad because somebody knocked over her blocks - and "Big News with Blue" is a recreation of "Blue's News" where the story is about Blue getting excited over Mr. Salt and Mrs. Pepper's new baby (or babies in the newer episode, in which they have twins). The new episodes use identical clues to the original episodes. Of course, chances are the very young target audience of Blue's Clues and You won't know enough about the parent series, which aired nearly three decades prior, to notice the recycling.
The plot of the Season 5 episode "Best Burger" is extremely similar to that of the Season 3 episode "Family Fracas" in that they both involve Bob and Jimmy Pesto competing against each other in a competition run by Chuck Charles, which Bob ultimately loses. However, "Best Burger" differs from "Family Fracas" by ending on a much better note for Bob; while "Family Fracas" had a full-on Downer Ending involving the Belchers being cheated off the show with neither the Pestos nor the producers facing any consequences for doing so, "Best Burger" has Bob just barely lose to a Nice Guy who won fair and square, Jimmy gets dead last in a humiliating fashion, and Bob's restaurant gets more business by the end so he doesn't leave empty-handed.
The plot of the Season 9 episode "If You Love It So Much, Why Don't You Marionette?" is strikingly similar to Season 3's "Carpe Museum", featuring Louise as she sneaks off during a boring field trip and discovers a closed-off area of the building that features something she finds much more fun, also showcasing an adult who helps her. It also features aspects of Season 5's "Hawk & Chick", with Louise wondering if growing up means losing who she is after meeting a female performer who changed for the worse with age. The key differences come from how the episodes use their plotlines—both "Carpe Museum" and "Hawk & Chick" used their respective plots to highlight Louise's close bond with Bob; meanwhile, "If You Love It So Much, Why Don't You Marionette?" doesn't really explore any character dynamics, since the primary people involved in Louise's plotline are all one-off characters.
Fitting for a Milestone Celebration, the general plot of the Season 11 episode "Bob Belcher and the Terrible, Horrible, No Good, Very Bad Kids" is a Call-Back to "Human Flesh", the very first episode of the series: both episodes revolve around the restaurant being in danger of getting shut down due to a combination of the Belcher kids' antics and Hugo's Jerkass attitude, Bob gives a "The Reason You Suck" Speech to the kids at one point and Ron gets Hugo to help reopen the restaurant again by the end.
The Courage the Cowardly Dog episode "Curtain of Cruelty" has an identical plot to "The Tower of Dr. Zalost"; a scientist causes the entire town of Nowhere to become miserable, just like him (cruel in the former episode and depressed in the latter), and the solution involves one of Muriel's homemade recipes (fabric softener in the former and "happy plums" in the latter). Also, Eustace is immune because of his curmudgeoness. Both episodes do have several differences though, for instance "Dr. Zalost" is a full 30-minute episode, while "Curtain of Cruelty" is a normal 15-minute short.
The Critic has an in-universe moment when Duke points out that Jay is in a rut by syncing up four separate Tom Cruise movie reviews that all follow the same template and end with Jay saying the exact same lame joke in unison with each other: "You might say he's on... Cruise control! Ah-HAAA! I JUST! MADE! THAT! UP!!"
The Daniel Tiger's Neighborhood episode "Daniel Doesn't Want To Go Potty" is similar to the Growing Up With Hello Kitty short "Going To The Bathroom". Both episodes involve characters being too excited to do something with a friend (Katerina for Daniel Tiger, Fifi for Hello Kitty) that they forget to go to the bathroom. When they suffer from a Potty Emergency, they miss the fun thing they were anticipating as a result of it, and their parent teaches them to go before leaving. However, the way it plays out in both is different: while Daniel makes it in time when he suffers from one, Kitty has an implied Potty Failure after falling over when running to the bathroom. Both also contain a scene in which the protagonist and their family are traveling somewhere, but have to go home because someone needs to use the bathroom (in Daniel Tiger, they were going to the supermarket, while in Hello Kitty, Kitty and her family were going out to eat).
The Daria episode "The Lab Brat" is basically a reworked version of the non-canon pilot—both involve Daria finding herself in an Imaginary Love Triangle with Kevin and Brittany, while Quinn is legitimately interested in getting Kevin for herself. Otherwise they go in different directions: "Lab Brat" has an apathetic Daria annoyed about Brittany's suspicions, while the pilot had a Darker and Edgier version of her purposefully toying with Kevin's emotions.
"The Daria Hunter," "Fair Enough," "Just Add Water" and "Anti-Social Climbers" all have the same basic premise: school event puts the whole cast in a strange environment, reduce Daria and Jane to one subplot among many and watch people interact. There are more specific similarities: all include some Barch/O'Neill shipping, "Hunter" and "Water" both have Helen and Ms. Li getting into a conflict, etc.
The Doug episode "Doug's a Big Fat Liar" has basically the same plot as the Under the Umbrella Tree episode "Jacob's Girlfriends'': a main boy character (Doug/Jacob) wants to go to a dance with one girl, but another girl asks him to go with her, so he lies to the latter girl that he can't go to the dance because he has a sick relative to take care of. But then the girl comes to his house to visit the sick relative, so his sister or sister-like friend (Judy/Gloria) disguises herself as the non-existent relative to help him maintain the lie.
There are two episodes with very similar plots, "Max and the Magic Carpet" and "Three's a Crowd". Both plots feature a character who is feeling ignored by their best friend (the former has Ord feeling ignored by Max playing with Quetzal's magic carpet while Cassie feels ignored when she and Emmy make a new friend but feels left out). Both characters lament over losing said friend and talk it over with their friends who encourage the main character to express themselves. The conflict in both episodes is resolved when Ord and Cassie talk to Max and Emmy respectively and they make up.
To a lesser extent, "All Together Now" also follows a similar plot where Max feels left out when Emmy and Enrique spend a lot of time together due to being the same age and working on the same school project together. Max laments over being left out but it is subverted when Max eventually learns to have fun on his own and the episode ends with everybody joining in on the fun.
DuckTales (1987) and TaleSpin both on The Disney Afternoon, did this with episodes that involved confusion over what the right date was ("Allowance Day" and "The Time Bandit", respectively), which led to an impending execution. The main character(s) were saved by a pilot (Launchpad and Baloo, respectively) who scooped away the clouds to reveal what day it really was (with an eclipse and a comet, respectively), proving who was right. Baloo mentioned that he was the first pilot who had ever done something like this, despite the fact that TaleSpin came out after DuckTales (1987). (It could be argued that because TaleSpin takes place in what appears to be The '30s, Baloo would have been the first chronologically; a view taken by at least one crossover comic.) It's worth noting that "Allowance Day" and "The Time Bandit" were written by the same writers.
The Rankin/Bass Productions special The Easter Bunny is Comin' to Town is basically a beat-for-beat remake of Santa Claus Is Comin' to Town, with the Easter Bunny and Easter traditions in place of Santa Claus and Christmas traditions. In both specials, the holiday icon first appears as an orphaned baby, found and raised by a small, secluded community of little people (the Kringle elves/the Kidville kids) who later become his helpers. When he grows up, he decides to take the goods his foster family produces (toys/eggs) and share them with the outside world. He takes his goods to a somber, gray town, where the joy-starved people love them, but the mean ruler (Burgermeister Meisterburger/Duchess Lily Longtooth) outlaws them, forcing the hero to find inventive new ways to sneak them in. This leads to the creation of many holiday traditions. Meanwhile, a giant enemy (the Winter Warlock/Gadzooks the Grizzly) tries to block the heros way, but then has a HeelFace Turn when the hero gives him a gift and becomes his ally. Both specials are narrated by S.D. Kluger, who delivers letters to the holiday icon, with the aim of answering the questions the letters ask about how all the holiday traditions got started.
Peter appearing on Jeopardy ("What is diarrhea?") from "Brian: Portrait of a Dog".
The "drive-by arguments" gag from "There's Something About Paulie".
The episode "The Splendid Source" was adapted from a short story of the same name which Richard Matheson wrote in 1956. It shows in that the episode's humor is much more sedate than the norm for the show, and is almost completely devoid of cutaway jokes.
The episode "Gronkowsbees" has a very similar plot to the King of the Hill episode "New Cowboy on the Block"; both episodes involve a famous football player moving into the main characters' neighborhoods, causing trouble and acting like total jerks, but the main characters defend the new neighbors at first despite everyone else being annoyed by them, then they eventually realize how awful their new neighbors really are and scheme to get them to move out.
While it's not exact, the episode "Quagmire's Mom," in which Quagmire is put on trial for his crimes and gets off by blaming all of his behavior on his mother, is strikingly similar to the film I Accuse My Parents.
The 13th season episode "Roasted Guy" and the American Dad! episode "The Great Space Roaster" have almost identical beginnings, (Peter/Roger requests his friends roast him, and winds up being genuinely hurt by the results) but go in very different directions afterwards. Roger exacts revenge against his family in a way that only Roger can, by pretending to straighten his life out and stop doing all the bad things his family pointed out he does while attempting to kill them without them getting suspicious. Peter declares that his friends aren't his friends anymore, then befriends a group of Gossipy Hens.
The episodes "Road to Rupert" and "Total Recall" both involve Stewie and Brian traveling to find Stewie's teddy Rupert. In the former, Brian unintentionally sells him at a garage sale and the duo track him down to Colorado, while in the latter, he's the target of a product recall and they set out to rescue him from the toy factory before he's destroyed.
"Quagmire's Baby" and "No Giggity, No Doubt" both center around Quagmire meeting and briefly living with an illegitimate daughter from one of his many sexual escapades, the main difference being that the girl in the former was a baby that he was completely inept at taking care of and the girl in the latter was a teen whose presence changed his demeanor.
The rather infamous ending of The Fantastic Four (1978) in which Mr. Fantastic tricks Magneto into surrendering through the use of a wooden gun had previously been used in an episode of The Marvel Super Heroes starring the Incredible Hulk, which was itself an adaptation of 1963's Incredible Hulk #6. The earlier use of this scheme made at least slightly more sense in that the Hulk had the good sense to not reveal his trick until after the villain had left.
An episode of The Flintstones titled "Christmas Flintstone" was expanded into an hour-long special called A Flintstone Christmas in 1977. Three of the songs in "A Flintstone Christmas" were recycled from "A Christmas Story", a TV special Hanna-Barbera made in 1972.
In "Franklin the Teacher" from Franklin, Franklin becomes concerned that his little sister Harriet isn't ready for school after he learns that Bear's little sister Beatrice already knows stuff like her numbers. He decides to become a teacher to Harriet, but none of his lessons seem to stick because Harriet just thinks they're having playtime. At the end of the story, Harriet helps to repair a chair, something she picked up on while playing with toy tools, and Franklin's parents explain that little kids learn a lot just by playing. In the All-CGI Cartoon spinoff Franklin and Friends, Harriet and Beatrices' dynamic has been adjusted so that they're both around the same age. In "Franklin's School," it's revealed that they're both starting school soon. Franklin has the idea to set up a pretend school to teach them both, this time with the help of his friends. However, once again, the two seem more interested in stuff like recess. When he laments that they're not learning anything and he can't get them to pay attention, Bear points out that they're little kids, and Snail points out that all they want to do is play. Franklin wonders how he can possibly teach them stuff like counting. His friends help him to think back to their lessons from Mr. Owl and realize that Mr. Owl made learning fun for them and they can help Harriet and Beatrice to learn by playing.
Garfield and Friends had a case where the same cartoon was made twice in one season, but once as a segment for each part of the show, and both had a similar name. These were "The Feline Philosopher" and "The Farmyard Feline Philosopher", where a character cannot do something they're good at because of an obstacle and asks the titular character for advice. Oddly enough, the U.S. Acres half of the show also used a similar plot in "The Old Man of the Mountain", which aired in between the two Feline Philosopher episodes.
"Clash of the Titans" from Season 7 recycled the plot of "Attack of the Giant Robots" from Season 2, with both being about Garfield waking up in the wrong cartoon.
The U.S. Acres episode "The Name Game" is similar to the earlier cartoon "Bedtime Story Blues", in which Booker and Sheldon change a well-known fairytale into something much different from the original story.
It's probably just a coincidence, but the last part of "Arise, Serpentor, Arise"! (G.I. Joe) and the entire episode of "Atlantis Arise!" (The Transformers) have a few similarities: the villains of the series attack Washington, D.C., are defeated by the heroes, and the treacherous character voiced by Chris Latta saves his leader (receiving no gratitude for doing so). Of course, Cobra don't ally themselves with mer-creatures, and the Decepticons don't create a new leader, but even so...
The Hey Arnold! April Fools' Day episode was a 30-minute version of their previous episode "Beaned"; both episodes involve Helga faking an injury long after she's actually healed from it to have Arnold take care of her. The resolution of these two episodes are completely different, though. In "Beaned," Helga's conscience gets the better of her for taking advantage of Arnold's kindness and she fakes her 'recovery' so that he's let off the hook. In "April Fools Day," when Arnold learns that Helga's faking her injury in order to prank him, he retaliates with an audacious prank of his own before she can spring her trap. (Since "AFD" is supposedly set post-movie, the differences in outcomes for each story show a subtle change in dynamic between the two - Arnold's passivity to Helga's aggression is slowly evolving into a good-natured 'contest of equals' between the two.)
An episode of I Am Weasel used this for a Take That!; Weasel and Baboon are filming a cartoon with the Red Guy as the director, and eventually Weasel points out that in the script, you can see the part where they crossed out "Bugs" and wrote in "Buster", and again the part where Red crossed out "Buster" and wrote in "Weasel".
The KaBlam! episode, "Won't Stick to Most Dental Work" borrows a similar premise to the Tiny Toon Adventures episode, "Thirteensomething". In both episodes, one of the two hosts leaves their show after a feud to pursue their own career and have great success in that venture (Henry opens his own restaurant, Babs stars on the titular Show Within a Show). Meanwhile, the other host (June and Buster) tries unsuccessfully to get a new co-host, inevitably leading to their show's downfall. Near the end of the episode, both parties realize how much they miss each other and reunite.
Kaput & Zösky is rather fond of this, recycling not just scripts but entire episodes themselves. One episode has them try to take over a planet, only to find all of its inhabitants fleeing because it is about to be destroyed at sundown. Kaput and Zösky try to flee, only to have the planet blow up beneath them. The episode is later repackaged as a new episode, with only new dialogue used, with the plot changed to the planet, this time a popular tourist destination, becoming unpopular.
Kim Possible gives us a Father's Day episode ("Mathter & Fervant") where teenage Ron doesn't want to hang out with his father, an actuary. The Dad then has to save the day to win his son's respect. The same plot is used in American Dragon: Jake Long with Jake and his father (also an actuary.) Both series used the same writing staff and the episodes premiered within 24 hours of each other, making the borrowing all the more egregious.
In addition, Kim Possible and Doug both have an episode ("Kimitation Nation" and "Doug's En Vogue") in which the main character inspires a fashion line, but it doesn't help their popularity at school, since everyone thinks they are just copying the look to get noticed. note Although the KP episode also had mad scientists and evil clones of the protagonist, which the latter episode lacked. It's perhaps worth noting that Kayte Kutch and Sheryl Scarborough, who wrote the former episode, were also writers on Doug.
"A Man Without A Country Club", where Hank is offered membership to Nine Rivers, an exclusive, Asian-only country club, but as a Token Minority so the club wouldn't lose a tour by Tiger Woods, is a Race Lift of the The Jeffersons episode "Tennis, Anyone?", where George is offered membership at an all-white country club whose charter might be revoked.
"Hank's On Board" is an interesting example. The plot (sans the ending) is identical to Adrift (2006), where a group of people go swimming off a boat and forget to lower the ladder. Adrift was released almost exactly one year after "Hank's On Board" was aired, but was written years earlier and was in production when the episode would have been produced.
The Lilo & Stitch: The Series episode "Skip" has a similar set-up to the episode "Anywhere But Here" from Sabrina: The Animated Series. Both involve Lilo and Sabrina respectively using an experiment/magical watch to become older after not being allowed to do certain things in their current ages. However, this trope is downplayed as this is where the stories are different. While Sabrina finds herself in a Bad Future where the snobby Gem Stone is her boss (among other crazy things), Lilo finds herself in a progressively worse future where Gantu and Hamsterviel have captured all of the experiments (save for Stitch and Skip) as she ages up twice. Luckily, both scenarios have a Reset Button to undo everything.
The episode "King Crab" recycles the plot of the Adventures in Wonderland episode "The Bunny Who Would Be King" from two years earlier. In both, the character who works as the monarch's head servant (Sebastian/the White Rabbit) is visited by family (Sebastian's parents/the Rabbit's brother Rabbit DeNiro). Unfortunately, they're under the mistaken impression that he is the king (though the White Rabbit actually lied that he was king in his letters, while Sebastian just wrote that he's "in charge of everything" and his parents misunderstood). So he and his friends create an elaborate scheme to make it look like he really is king and to keep the family member(s) from meeting the real monarch (King Triton/the Queen of Hearts).
On The Little Rascals, Rowby Goren's script for "Rock & Roll Rascals" was reused by Earl Kress as "The Zero Hero", replacing Darla's favorite rock singer with her favorite TV superhero actor.
"Tin Pan Alley Cats" uses the same panning shot over Wackyland as "Porky in Wackyland". "Dough for the Do-Do" is a shot-for-shot colorized "Porky in Wackyland".
Friz Freleng even recycled a few of his own Looney Tunes scripts within Looney Tunes itself. For example, the basic plots of "His Bitter Half" and "Honey's Money" are the same: A money-grubbing man (Daffy Duck in the former, Yosemite Sam in the latter) marries a woman for her money, and eventually has to take care of the woman's son. They even share a scene: The shooting gallery where the son makes it seem like Daffy or Sam is shooting at the barker. "Hmm...must have rick-o-shetted!"
The 1949 short Mouse Wreckers was remade in 1958 as Gopher Broke. It revolves around a duo of mischievous rodents (Hubie and Bertie in the former, the Goofy Gophers in the latter) trying to drive a much larger foe (Claude Cat and the Barnyard Dawg respectively) insane to infiltrate the building they're trying to sleep in.
The DePatie-Freleng Enterprises-era Daffy Duck cartoon Suppressed Duck has a very similar plot to the 1955 Donald Duck cartoon Beezy Bear. Both cartoons revolve around a boundary being drawn for the bears to stay on one side and the duck to stay on the other. The primary difference is that in Suppressed Duck, the bear isn't the one breaking the rules.
Along Came Daffy is essentially a colorized version of Daffy's Southern Exposure, in which Daffy stumbles upon a cabin occupied by a starving duo who intend to eat him. In the original, it was a fox and a weasel; in Along Came Daffy, they are replaced by Yosemite Sam and a black-haired lookalike of him.
Not only is the show similar in premise to Stuck in the Middle, but they both have episodes where the main character tries to claim the best seat in the family car.
"Undie Pressure" is similar to the Ed, Edd n Eddy episode "All Eds Are Off" as both are about the characters entering a bet to see which of them can go without their annoying habits the longest for a reward.
"Ties That Bind" is similar to the Muppet Babies (1984) episode "Eight Take-Away One Equals Panic" and The Powerpuff Girls (1998) episode "Little Miss Interprets", all three plots revolving around some misunderstandings leading to a belief among the kids of the family (The Louds, the Muppets, and the PPG, respectively) that their guardians are going to get rid of them.
"One of the Boys" is similar to the Dexter's Laboratory episode "Oh, Brother"; both of which involve the main characters ending up living with brothers instead of sisters, only for it to be not as cool as they thought it would be.
The episode "Pipe Dreams" has a similar premise to "Serious Business" from Teen Titans Go!, in which one character is so fed up with people taking long in the bathroom that they come up with their own solution to the problem, which is different for both shows (in Titans, Robin establishes a 5-minute rule, while in Loud House, the parents build their own bathroom).
"Making The Grade" is similar to the The Simpsons episode "Bart The Genius", in which one of the main characters gets admitted to a higher-level educational institute, only to find out that it's not as great as they wanted it to be.
"For Sale By Loner" borrows a similar plot to the SpongeBob SquarePants episode, "Squidville". In both episodes, one character (Mr. Grouse, Squidward) moves away from their neighbors (The Loud Family, SpongeBob and Patrick), and at first, they like their new life of peace and quiet, but soon find it dull with nothing to do. Eventually, they start to get on their new neighbor's (Mr. Bolhofner, the citizens of Tentacle Acres) nerves by doing things their old neighbors would have done, and eventually move back to their old home.
The Magic School Bus episode "Inside Ralphie" is very similar to the Muppet Babies (1984) episode "Scooter's Uncommon Cold": a "Fantastic Voyage" Plot where one of the characters gets sick, the others all shrink themselves and go into his body, and they learn about the immune system by seeing how their friend's is working to make him well. The main difference is that the Muppet Babies only imagine themselves going inside Scooter, while Ms. Frizzle and her class go inside Ralphie for real.
The Mighty B! episode "Dogcatcher in the Rye" has the same plot as the Rocko's Modern Life episode "Ed Good, Rocko Bad". Both center on the protagonist running for dog catcher against their archenemy, only for the latter to use slander against the former to win.
Two Lila-centric episodes, "Chameleon" and "Ladybug", are identical in the fact that everyone in school believes Lila's stories (especially those concerning her health), and Marinette gets ostracized, but she gets more support from her friends the second time. More generally, Lila is The Dragon in all seasons finales but the third.
In general, the gimmick of turning all of Marinette and Adrien's classmates into new reservist superheroes can be seen as the recyclage of the idea of turning them into new Monsters of the Week in season 1.
In the 1984 series' episode "Dental Hyjinks," Fozzie hurts his tooth, but is afraid to go to the dentist to get it fixed, and spends the whole episode trying to get out of going. But in the end it's not scary at all, and he gets a Post-Treatment Lollipop, which leads to all the other kids to pretending to have toothaches so they can go to the dentist too. In the 2018 series' episode "Animal Gets the Sneezies," Animal can't stop sneezing, but is afraid to go to the doctor to find out why, and spends the whole episode trying to get out of going. But in the end, of course, it's not scary at all, and he gets a Post-Treatment Lollipop, which leads to Gonzo pretending to sneeze so he can go to the doctor too.
Both series also have a Cinderella Plot episode: "Pigerella" from the original series (with Piggy as Cinderella and Gonzo as her "Fairy Godwierdo") and "Gonzo-rella" from the reboot (with Gonzo as Cinderella and Rizzo as his "Fairy Ratfather").
In two different episodes, the kids build their own pretend theme park: Season 4's "Muppetland" and the series' final episode, "Eight Flags Over the Nursery." Preceding both of them, Season 1's "Fun Park Fantasies" also has the kids imagine themselves at an amusement park, although in that episode they don't actually build one. It helps that each episode has a slightly different kind of park: in "Fun Park Fantasies" they imagine a place with old-timey carnival rides like a fun house and a merry-go-round, in "Muppetland" they build a park that's more like Disneyland, while in "Eight Flags Over the Nursery" the park is like a cross between a Six Flags park and Universal Studios.
Two episodes have the kids imagining themselves as various Nursery Rhyme characters: Season 3's "Muppet Goose" and Season 6's "Goosetown Babies."
Two episodes feature retellings of Peter Pan. In Season 2's "By the Book," Scooter and Skeeter share the role of Peter and Kermit takes the place of Wendy, while in Season 8's "Kermit Pan," Kermit plays Peter, Skeeter plays Wendy and Scooter plays Smee, and in both episodes, Piggy plays Tinker Bell, Rowlf and Fozzie play John and Michael, Gonzo plays Captain Hook and Animal plays the crocodile.
In "The Ticket Master", Twilight is given two tickets to the Grand Galloping Gala. She takes one for herself but can't decide on which of her then-new friends is most deserving of the other and eventually the whole town pesters her for the ticket. An episode of My Little Pony Tales had a similar premise. In "And the Winner Is...", Clover is given two concert ball tickets and can't decide on who deserves the extra one.
"Ponyville Confidential" bears similarities to the Ed, Edd n Eddy episode "Truth or Ed" and the SpongeBob SquarePants episode "The Krabby Khronicle", where the characters get involved in a slanderous newspaper business.
"Sisterhooves Social": Rarity and Sweetie Belle get on each other's nerves to the point where Sweetie Belle disowns Rarity as a sister. The two meet again later on a camping trip Sweetie Belle is having with Applejack and Apple Bloom, but tensions remain high between them. Sweetie Belle realizes that Rarity is a sister worth having after participating in, although not winning, the Sisterhooves Social race. "Oh, Brother!": Mario and Luigi get on each other's nerves to the point where Luigi disowns Mario as a brother. The two meet again later in the middle of a rainstorm, but tensions remain high between them. Luigi realizes that Mario is a brother worth having after saving him from one of Bowser's schemes.
"Hearts and Hooves Day" is similar to The Powerpuff Girls' "Keen on Keane". It involved the trio being Shipper on Deck and ensuing disasters. The love interest is both cases is a female kindergarten teacher (Ms. Keane, Cheerilee) and an older male relative (Prof. Utonium, Big Macintosh.)
"Putting Your Hoof Down" recycles the premise of another Powerpuff Girls episode entitled "Bubblevicious". Both stories involve the most sensitive main character wanting to prove that she has a spine, and ends up going too far with her newfound confidence.
A possibly unintentional one, but "A Canterlot Wedding" is similar to parts of the South Park episode "Succubus". Both involve the protagonist(s) finding something off about their friend's fiancee and accuse her of being evil, leading to her running off in tears and the friend to call out the protagonist(s) even though (s)he/they was/were right in a way. The difference is that while the South Park boys hated Chef's fiancee Veronica from the start and she was clearly an evil monster, Twilight Sparkle's reason was more tragic because the wedding was between her older brother Shining Armor and her beloved foal-sitter Princess Cadence, who turns out to have been kidnapped by Queen Chrysalis, the ruler of the Changelings who happens to prey on Shining Armor's love by taking on Cadence's form.
"Maud Pie" is similar to the Hey Arnold! episode "Weird Cousin". Both episodes have a character's rather peculiar relative visit the main cast. Coincidentally, Pinkie Pie's sister Maud speaks in the same monotone as Arnold's cousin Arnie.
"Magical Mystery Cure" and "Crusaders of the Lost Mark" share a similar formula: both are Musical Episodes where the protagonists undergo a major transformation after solving a major cutie mark-related issue. In the former, Twilight grows wings after figuring out how to return her friends' swapped cutie marks to normal and is crowned a Princess of Equestria. In the latter, the Cutie Mark Crusaders discover they share a talent for helping others understand their own talents after helping Diamond Tiara through a mark-induced identity crisis, which leads to them earning their cutie marks.
The episode "Rarity Takes Manehattan" is very similar to the Family Ties episode "Designing Woman" where Mallory finds out a co-worker is stealing her fashion design ideas.
It also has much in common with an episode of its sister show, Littlest Pet Shop (2012), "Plane It On Rio!" In both episodes, a fashionista travels to a distant city to participate in a major event and meets an old acquaintance, who proceeds to steal and plagiarize the fashionista's ideas, and she resolves the issue by creating even better designs to defeat her unscrupulous rival. Both episodes also debuted within a month of each other.
"The Crystalling" involves the birth of Shining Armor and Princess Cadence's baby Flurry Heart. Upon birth, she involuntarily uses her magic. That aspect is similar to "Fairly Odd Baby", in which the newborn Poof has no control over his magic. Coincidentally, the baby's cry causes something bad to happen, although the danger triggered by Flurry Heart's crying was by accident.
The episodes "The Mysterious Mare-Do-Well" and "28 Pranks Later" have almost identical basic plots. In them, Rainbow Dash is acting more obnoxious than usual, so the other ponies form a plan to take her down a peg and teach her the error of her ways (inventing a superhero to upstage her at every turn and staging a Zombie Apocalypse, respectively).
"A Flurry of Emotions" is pretty much "Baby Cakes" with Twilight in Pinkie Pie's place, as she looks after her niece Flurry Heart.
The episode "Secrets and Pies" is similar to the My Friends Tigger & Pooh episode "Piglet's Thousand and One Watermelons".
"A Matter of Principals" is very similar to "The Cutie Re-Mark", both being episodes about an antagonist targeting a protagonist as payback for taking something they wanted, one-on-one because said antagonist removed the protagonist's allies from the equation, with the antagonist causing a ton of damage and endangering everyone else, with the protagonist juggling battling the antagonist and trying to clean up the mess, and the antagonist ultimately being too powerful to defeat and effectively getting what they want in the end to make them stop.
The Mysticons episode "Quest of the Vexed" shares the same plot to the My Little Pony: Friendship Is Magic episode "All Bottled Up". Both centered around a character being angry at someone and they use some kind of magical object to bottle up their anger, only for the object to break and spread the anger to everyone around it.
The PAW Patrol episode "Pups Save A Stinky Flower" has a similar plot to The Doodlebops episode "The Eew Flower", where a character brings their friends a smelly flower that they think they would like, but their friends do not want it. It also shares the same plot with the Granny Garbanzo plot in The Big Comfy Couch episode "Honest To Goodness".
"Pups Save a Snow Monster" is very similar to "The Yeti" from The Backyardigans, where the cast looks for the titular Monster, and one character (In Backyard, it's Tasha, in PAW, it's Ryder) tries to convince the others that there's no monster. In the end, it turns out there actually was a monster, but it's really just their friend covered in snow. In Backyard, it's Pablo, in PAW, it's some farm animals.
The show also had two episodes ("Pups Turn On the Lights" and "Pups Save a High Flying Skye") where a Big Blackout prevents the someone from doing something that they were planning for a while (in the former, the blackout ruin's Chase's birthday, while in the latter, a farmer cannot do work because of it).
The Pinky Dinky Doo episode "Pinky Dinky Re-Doo" has the same plot as The Big Comfy Couch's "Ain't It Amazing, Gracie?". Both involve characters losing a beloved item and trying to retrace their steps to find it and end with a relative giving them the item that they lost.
Many Popeye cartoons from Famous Studios were remakes of old Fleischer Studios shorts, such as "The Anvil Chorus Girl" (based on "Shoein' Hosses") and "Penny Antics" (based on "Customers Wanted").
The plot of "Olive's Boithday Presink", especially the gag of the hunted tricking the hunter into thinking he has a family, was reused in the Looney Tunes short "Duck Soup to Nuts". Both were written by the same guy.
"Olive Oyl for President" had the exact same script as "Betty Boop for President", replacing Betty with Olive, of course.
Famous Studios also repeated the plot of 1936's "Christmas Comes But Once a Year" (Starring Grampy from the Betty Boop shorts) in the 1952 Casper the Friendly Ghost short, "True Boo" with both involve helping a sad child/children on Christmas by turning household items into toys (or in this case, the exact same item-made toys).
The episode "What's The Big Idea" borrows a similar premise to the Adventures of Sonic the Hedgehog episode "Too Tall Tails", in that the villain grows one of the main characters (in The Powerpuff Girls' case, the whole trio) to gigantic size so that they cause more harm to a city than good.
The Powerpuff Girls Movie is almost an expansion of "Mr. Mojo's Rising", detailing about how the girls were created and how Mojo Jojo became who he is today.
The episode "Bubblevision" to "The Mane Event". Both have one of the sisters get an embarrassing attribute (A bad haircut for Blossom, and Nerd Glasses for Bubbles), the two other sisters laugh at her which causes her to lose confidence, but in the end, she uses the attribute to defeat the monster attacking the town.
"Strong Armed" has similarities to "Bubblevision". Both include Bubbles having a medical condition, with the former having her break her arm and the latter revealing that she is near-sighted.
"Arachno-Romance" is similar to "Mommy Dearest" in that the Professor gets a girlfriend but his daughters don't like her.
"Man Up" is almost exactly the same as "Makes Zen to Me".
The crossover with Teen Titans Go! has a similar plot to "Members Only". An older group of superheroes acts condescending towards the Powerpuff Girls, though in this case it's due to their age rather than gender. It also has elements of The Powerpuff Girls Movie with Mojo Jojo commanding an army of simians.
The Recess episode "The Hypnotist" has the same basic scenario as the Rugrats episode "Regarding Stuie": the show's most important adult male is somehow made to believe he's a child, befriends the main kid characters and has fun with them, but eventually the kids realize they need to change him back. In the Rugrats episode, Stu becomes baby "Stuie" due to Easy Amnesia from a bump on the head, but after a while Tommy misses his dad; in the Recess episode, Principal Prickly becomes six-year-old "Petie" due to a hypnotism act gone awry, but when Miss Finster takes over the school in his absence, the kids realize they want Prickly back.
The Redwall animated series has a weird example. Season 1 is adapted from the first book, but it includes an episode titled "Cluny's Clowns" in which Cluny the Scourge attempts to infiltrate and take over Redwall Abbey by disguising his goons as circus performers. This didn't happen in the original book, but a similar scenario did happen in the book's direct sequel, Mattimeo, when Slagar the Cruel disguises himself and his goons as circus performers to infiltrate the Abbey and kidnap the children. The show would later adapt Mattimeo for Season 2, making it seem like they were reusing the Circus Episode plot when, in reality, Mattimeo actually did it first.
Mordecai and Rigby mess up/break something and must repair it. In most of the episodes that had this plot, it'll usually end up with a "Shaggy Dog" Story. (ex: "Limousine Lunchtime", "Tent Trouble", "Garage Door")
Mordecai and/or Rigby wanting to accomplish at something, usually a video game. (ex: "High Score", "Slam Dunk", "Bank Shot", "Happy Birthday Song Contest")
Mordecai trying to impress Margaret in the first four seasons.
"Rigby's Body" has an eerily similar plot to the Aaahh!!! Real Monsters episode "Who'll Stop the Brain", in which Ickis and Krumm try to search for Oblina's brain after sneezing it out from studying for an exam to the point of exhaustion after being warned previously like Rigby when his consciousness has to be retrieved after being forcefully yanked out of his body from eating too much junk food.
The episode "Fortune Cookie" has a similar plot to the Rocko's Modern Life episode of the same name, where, after being deemed Mr. Lucky, Filburt gets bad luck after his fortune cookie says so. The Regular Show version has Benson, after a streak of insanely good luck, suffering from terrible luck as a result of Rigby swapping their fortunes.
Rocket Power the episode "Wrath of Don" is quite similar to Hey Arnold! "Eugene Goes Bad" and Sabrina: The Animated Series "Feats of Clay" as all three episodes revolve around famous actors who the main characters are dismayed to find out don't do their own stunts and are kind of prima donnas, whereas the actors in Sabrina and Hey Arnold actually turn out to be pretty decent guys who are heroic in their own right, the actor in Rocket Power is a massive Jerkass who nobody really likes.
The episode "Snow Day" is quite similar to the Hey Arnold! episode "Hooky" as both revolve around the main characters skipping school and missing out on an exciting event, whereas in "Hey Arnold" the kids manage to avoid getting caught, in "Rocket Power" Otto and Sam both end up getting caught.
The episodes "Million Dollar Abie" and "The Boys of Bummer" both involve a member of the Simpson family (Grampa and Bart respectively) becoming a pariah over a sports-related mishap, to the point they attempt suicide. Though in the former's case, it only took over the first act, whereas the latter became the episode's main dilemma.
The episodes that focus on Homer and Marge's marriage crisis, Homer getting a job, Bart getting a new girlfriend, Homer trying to be a better father, and Lisa wanting to be popular (usually when she befriends a one-time character). They're the most used plots in this show.
"Bart Sells His Soul" had Moe remake his bar into Uncle Moe's Family Feedbag to make more money. Later episodes had him remake the bar into a swanky hipster joint and an English-style restaurant, although the conflicts addressed in each episode are subtly differed, and the bar usually was only the starting point.
The subplot for "Realty Bites", where Snake tries to kill Homer when he buys his car at a police auction, was previously used in The Flintstones episode "Fred's Second Car".
The main plot of South Park: Bigger, Longer & Uncut is an extended musical version of the subplot in "Death". Here, Kyle's mom overreacts to Terrance and Phillip and gets the other parents to protest against them, only in this case it escalates into a war between the United States and Canada.
Another episode of Spider-Man (1967), involving a scientist taking over a power plant to raise the city into the air, was re-used later. Essentially they changed a few words in the script, changed the scientist's skin color and added pointy ears, and suddenly it was involving an Atlantean using his submarine to lower the city into the ocean.
A few later episodes of SpongeBob SquarePants seem to have recycled plots from other Nicktoons. "Toy Store of Doom", for example, has essentially the same plot as the Rugrats episode "Toy Palace" (they get locked in the toy store after it closes for the night and are afraid the toys will attack them), while "Banned in Bikini Bottom" (Krabby Patties are outlawed and Mr. Krabs starts selling them at SpongeBob's house secretly) is similar to the CatDog episode "Just Say CatDog Sent Ya," in which Farburg Burger Bones are banned from Nearburg and CatDog starts selling them at a speakeasy in an underground cellar.
"Picture Day" was a recycled script from the Recess episode "One Stayed Clean". An earlier episode recycling a script from the show would be "Big Pink Loser", which was almost identical to "Copycat Kid".
"Fear of a Krabby Patty" partially recycles its plot from the earlier SpongeBob episode "Graveyard Shift". Both episodes involve Mr. Krabs changing the Krusty Krab's business hours to run for 24 hours a day, despite not having the staff necessary to do so, but for different reasons; in "Graveyard Shift", it's because he discovers that he can get more customers if the Krusty Krab was always open, and in "Fear of a Krabby Patty", it's to spite Plankton after he opens the Chum Bucket for 23 hours, setting the latter's plan for the episode into motion. The main difference is that in "Graveyard Shift", we only see the Krusty Krab open for one night shift, and in "Fear of a Krabby Patty", it's open for 43 days straight.
"Sandcastles in the Sand" has a similar premise to "The Snowball Effect", where SpongeBob and Patrick get carried away in an escalating war with sand and snow respectively. The difference is that Squidward doesn't appear in "Sandcastles".
"Krab-Borg" borrows a similar premise to the Rugrats episode "Real or Robots?", wherein two characters believe another character is a robot after seeing a scary robot movie.
"To Love a Patty" has the same premise as The Ren & Stimpy Show episode "I Love Chicken", where a character falls in love with a food item that they were preparing for someone else.
"Born Again Krabs" and "Cuddle E. Hugs" both have their plots started by a character eating a clearly rotten Krabby Patty because they believe it's still good.
"Squilliam Returns" and "Grandmum's the Word" both involve a member of the main cast pretending to be the owner of the Krusty Krab to impress a minor character.
"Best Frenemies", "The Other Patty", and "The Krusty Bucket" all have Mr. Krabs and Plankton forming an Enemy Mine to combat a new restaurant that threatens to put them out of business, though they're teamed up for most of the first and only begrudgingly team up later in the other two.
"The Paper" and "Idiot Box" both involve SpongeBob doing a lot of fun things with an ordinary object due to his imagination and then Squidward trying to do the same thing with said objects and being unable to do so.
"Nasty Patty" is quite similar to the Rocket Power episode "It Was a Dark and Stormy Day"; both episodes take place on a rainy night with the main characters assuming that someone else was killed and both episodes also mostly take place in the Local Hangout restaurant of the series (Krusty Krab/Shore Shack), and in both episodes the cops get involved and both end with an "Everybody Laughs" Ending with the cops and main characters hanging out in the restaurant.
At least three episodes have plots similar to ones that were previously done by Rocko's Modern Life; "No Nose Knows" to "Nothing to Sneeze At" (a character with no nose gets one and it changes their life), "Broken Alarm" to "Commuted Sentence" (the main character keeps trying and failing to get to work on time to keep their job), and "SpongeBob's Bad Habit" to "Tooth and Nail" (the main character develops a sudden nail-biting habit). The latter episode also shares a plot with the Lamb Chop's Play-Along episode "Stop Biting Your Nails".
"All That Glitters" and "Evil Spatula" both revolve around SpongeBob breaking his spatula and getting a new high-tech one to replace it.
"Gone" borrows a similar premise to the Foster's Home for Imaginary Friends episode, "Squeeze the Day", wherein the main character (SpongeBob, Bloo) discovers that all of his friends have gone missing, so he at first worries where they are, then tries to live his life without them. The main character then discovers that his friends have gone somewhere and didn't invite him. (SpongeBob's friends were celebrating No SpongeBob Day, while Frankie, Madame Foster, and the imaginary friends went to the beach).
The basic plot of "Imitation Krabs" (Plankton disguises himself as Mr. Krabs to steal the formula) was reused multiple times with Plankton disguising himself as different characters: "Someone's in the Kitchen With Sandy" (Sandy), "Gramma's Secret Recipe" (SpongeBob's Grandma), "Shellback Shenanigans" (Gary) and "Married to Money" (a sentient wad of money called Cashina).
When sci-fi author Larry Niven was hired to write an episode of Star Trek: The Animated Series, he took the plot of his short story "The Soft Weapon" and replaced three of the characters with Enterprise crew to create "The Slaver Weapon". It even featured one of his trademark alien species, the Kzinti, without alteration. (His rejected original proposal for the episode, meanwhile, became another short story, "The Borderlands of Sol".)
The Star vs. the Forces of Evil episode "St. Olga's Reform School for Wayward Princesses" is very much like the Phineas and Ferb episode "Phineas and Ferb Get Busted!"; both involved a character trying to save loved ones from an Assimilation Academy that's stripping them of their identities. Incidentally, they had the same writer.
The entire premise of the show is very similar to the episode "Jack and the Flying Prince and Princess" of Genndy Tartakovsky's Samurai Jack. Both even feature their robot companion dying, only in Sym-Bionic Titan, said robot is revived.
The Team Umizoomi episode "Job Well Done!" is similar to the Noddy's Toyland Adventures episode "Noddy Buys A Parasol", in which a child character tries their hand at a few jobs to earn money to get something they want.
The 1970s TV episode "Stay Awake or Else..." is similar to the theatrical short Sleepy-Time Tom, in which Tom returns home sleepy from a party and is in danger of losing his job if he's caught sleeping by his master.
In the mid-to-late-1950s, some MGM cartoons were re-animated in Cinemascope with recycled audio. This includes the Tom and Jerry cartoons Tops with Pops (a remake of Love that Pup), Feedin' the Kiddie (a remake of The Little Orphan), and The Egg and Jerry (a remake of Hatch Up Your Troubles).
A slightly less blatant example is The Vanishing Duck, which recycles the premise of The Invisible Mouse 11 years earlier.
Total Drama: The season two episode "Super Hero-ld" shares many similarities with the season one episode "Hide and Be Sneaky", in which the remaining male contestants form an alliance to overthrow the girls. The challenge in both episodes involve Chef Hatchet assaulting the contestants in some way. During the elimination ceremony, Duncan successfully decides on the elimination of one of the girls (Bridgette and Leshawna) since their biggest threat (Heather and Courtney) had immunity that night. One of the guys (Geoff and Harold) was hesitant on voting their partner (Bridgette and Leshawna) off, but said girl was voted off. It is also worth noting that Duncan is a member of both alliance, although he does not form the second one. The only thing that stands out from the similarities was in the second season, the girls (Beth, Leshawna, and Lindsay) almost succeeded in voting off Duncan, while in the first instance the girls could not agree on which guy was more viable for elimination at the time between Duncan (whom Bridgette suggested) and Owen (whom Heather suggested).
Take a typical episode of Wacky Races, find a visual gag involving Dick Dastardly's attempt to stop the other racers, and the odds are even that you'll find an identical gag in a Chuck JonesRoad Runner cartoon. (Michael Maltese is credited as a writer on both series.)
The Yin Yang Yo! episode "Touchy Feelings" was about Yang having all of his emotions magically removed, much like Timmy in The Fairly OddParents episode "Emotion Commotion". Creator Bob Boyle was a staff member on the latter series.