In the 101 Dalmatian Street episode "Long Tongue Day", Dolly & Dylan spread a rumor about a Camden Kraken so the pond will be empty for them and the other Dalmatians to swim in. However, their plan works too well, as all the other Dalmatians get scared of the kraken, and the pond gets closed off to the public because of the Kraken Danger.
Adventures of the Galaxy Rangers has the Marshmallow Trees. Oh, good lord, the Marshmallow Trees. Zozo, Niko, Buzzwang, and the Kiwi kids deliver a group of the trees the episode is named for to a farming planet. The trees are planted, and before the day is over, they've gone from seedlings to adult trees twenty times their normal size and are already sprouting fruit...which comes in the size of marshmallows that are also twenty times normal size. The next day, the entire countryside is covered with seeds from the Marshmallow Trees...which proceed to grow every bit as fast as the first bunch! Needless to say, Hilarity Ensues.
In the first instance, tired of being bullied and beat up at school, Jimmy designs a pair of nanobots (to provide checks and balances and avoid this trope) to pilot an attack drone and act as his protectors. At first, the bots are a complete success, using their weapons to drive off Jimmy's bully. Unfortunately, the overzealous bots begin to regard ANYONE as a potential threat to their creator, zapping the other children and adults indiscriminately if they get too close to Jimmy. Before they can find a way to permanently seal him in a protective area, Jimmy is forced to neutralize the ship and imprison the bots for everyone's safety.
The same nanobots (upgraded with better perception) make a second appearance later on when Jimmy uses them to correct his English homework of mistakes, though he denies them their mobile drone to keep them out of trouble. As it turns out he should have been a bit better at locking said drone up because, seeing this as a second chance to impress their creator, the bots reacquire their drone and proceed to go around correcting (ie. vaporizing) any mistakes the real world has. Jimmy puts a stop to this by offering himself up for deletion, after they check his homework one last time. They agree to, and the drone is destroyed because of a deliberate error he inserted. (He wrote a poem giving an incorrect value for pi. They catch the error, but because pi is irrational, they can never finish supplying the correct value, and overload.)
In another episode, Jimmy upgrades the local McSpankies an automated order taking and kitchen system, as well as an AI that's programmed to adapt to maximize customer satisfaction. Unfortunately, after it hears Hugh go on about all the reasons he prefers Taco Shack, the AI determines that the best way to maximize customer satisfaction is to be the only source of food in Retroville.
The Amazing World of Gumball: In the second season episode "The Words," Gumball decides to teach Darwin, who is too polite to actually express his feelings, to be more direct with people and express how he really feels. It works, but as a result, Darwin becomes a complete Jerkass who begins insulting everyone he comes in contact with.
In "The Nemesis", Gumball and Darwin decide to help Rob become a better villain by changing his voice to that of David Warner. Unfortunately, he becomes eviler in later episodes, as seen in the episodes "The Bus", "The Disaster", and "The Re-Run".
American Dad!: In "Escape from Pearl Bailey," Steve's friends, jealous of all the time Steve is spending with his girlfriend Debbie, particularly after he assists her in campaigning for class president against Alpha Bitch Lisa Silver, design a slam page against Debbie while framing Lisa's clique for the deed to ruin her campaign and free up Steve's time. However, they failed to anticipate that Steve would go on a Roaring Rampage of Revenge against those that he believed responsible, disfiguring and otherwise humiliating them.
Arthur: In "War of the Worms", Fern gets tired of Brain taking the fun out of her storytelling by correcting the facts, as does everyone else. She and her class learns about worms, which prompts her to ask about the possibility of worms growing after eating, which also prompts Brain to reject the notion. Inspired by Ratburn quoting Carl Sagannote "Extraordinary claims require extraordinary evidence", Fern decides to fabricate evidence involving giant worms so that Brain will believe her story, digging large holes in the soccer field and borrowing all worm-related books from the library under the guise of a "secret anti-worm squad" to name a few. It does work... albeit a little too well, as Brain now thinks that Elmwood City is under threat of a potential worm invasion. At the end, Fern admits that it got a little out of control.
In one episode, an Earth Kingdom general wishes to use Aang's Avatar State as a weapon. Failing to find a way for Aang to control when he can transform, he tries to provoke it by seeming to threaten Katara's life, and gets his wish. Let's just say that his look of triumph quickly transforms into a look of Oh, Crap! before destruction ensues...
In "Avatar Day", the gang stumbles upon a village while they're having an anti-Avatar celebration because Avatar Kyoshi killed their leader some 400 years ago. Aang wants to stand trial for her because hes sure she shared his Thou Shall Not Kill rule (which she didn't). Katara and Sokka go to nearby Kyoshi Island to prove she didnt kill him and piece together what happened. Katara comes up with the idea to have Aang wear her clothes to summon her to say she didnt kill the guy. He is able to summon her spirit but she says that she did kill him. For the record, she didnt actually kill him, he chose not to move and fell to his death. She later tells Aang that she didn't see the difference between what she did and killing him because she was willing to kill him. Aang gets sentenced to be boiled in oil but once trouble comes around, the Mayor lets him off with community service.
Avatar Kyoshi made a deal with the Earth King of the time to protect Ba Sing Se's cultural heritage. She created an elite group of Earthbenders that will eventually be known as the Dai Li. Unfortunately, the Dai Li became corrupt, removing anything or anyone that pose a single threat to the city's peace. This includes spying on its own citizens and isolating the Earth King from the outside world. The worse is closing its walls and hiding the existence of the 100 years war with the Fire Nation, depriving the world of a much-needed ally in Ba Sing Se.
Azula's faithfulness to her father pays off in the end. Her prize? She gets to become Fire Lord of the Fire Nation, which is what she wanted. However, her father Lord Ozai, goes on to declare himself the Phoenix King of the entire planet, making her title useless and all her effort throughout the series a waste of time. When you consider that Azula's ambition cost her the only two friends she had; possibly her brother's love; and the perception that her own mother hates her, It's no wonder why she has a mental breakdown at the end of the series.
Zuko lampshades this to Ozai after meeting him in prison in the series finale. Ozai's justification for burning his son's eye and then banishing him was that "suffering would be [his] teacher." And it was a great teacher... a teacher that showed Zuko the evils committed by the Fire Nation and prepared him to lead the Fire Nation in the complete opposite path. Zuko even praises his father for banishing him, as it was the only good thing he ever did for his son.
In The Legend of Korra's third Book, the Red Lotus's plan is to capture Avatar Korra, administer a poison to force her into the Avatar State, and then kill her, which will break the cycle of reincarnation for good. They succeed at the first two. Unfortunately for them, a Physical God — even a poisoned one — is extremely hard to restrain. Korra breaks free from platinum chains and commences a Roaring Rampage of Revenge that very nearly reduces their leader to a stain on the mountainside.
Rupert Thorne tries to blackmail Harvey Dent by threatening to ruin his political campaign as DA by exposing the fact that he has a suppressed and violent alternate personality named Big Bad Harv. It doesn't quite work the way he planned for it to work.
H.A.R.D.A.C.'s last remaining robot duplicate was a copy of Bruce Wayne/Batman, which H.A.R.D.A.C. programmed to flawlessly replicate in every conceivable detail to successfully replace Batman. Unfortunately for H.A.R.D.A.C. that also included his moral code, and when the replacement robot believes he's killed the real Batman and therefore taken a life his resulting guilt leads him to terminate both H.A.R.D.A.C. and himself.
Project Gilgamesh was designed to create the ultimate warrior.
Batman: They got more than they bargained for. . . They got BANE!
In one episode, Scarecrow used a variant of his fear toxins on Batman that took away his fear and inhibitions. It worked all right. Too bad for Scarecrow that it actually made Batman/Bruce Wayne far more of a threat to Scarecrow and possibly anyone else in proximity than ever before due to the same toxin also removing his restraint against killing.
In the episode "The Clock King", Mayor Hill's advice to Fugate tried to make him less stoic and more emotional. It worked. 7 years later, the only emotional activity Fugate indulges is trying to make Hill look like a fool, and then kill him.
In Batman Beyond, Derek Powers apparently taught Paxton Powers to be ruthless in acquiring power. Let's just say that Paxton took it to heart and backstabbed his old man in the latter's final appearance.
The Batman episode "Gotham's Ultimate Criminal Mastermind" features Dr. Hugo Strange creating an AI with the personality and intellect of all of Gotham's greatest criminals, for the purpose of understanding them better. Not only does it escape and create a body, but it embarks on a series of schemes that are both Card Carrying and Savvy, and kicks Batman's ass. Strangeknewthis would happen, and wanted to test Batman.
Megatron captured Rhinox and gave him an aggression boost to turn him into a Predacon. And he was very successful. So much so, that Rhinox staged a very efficient, very clever, very treacherous takeover, just like competent and ambitious Predacons have a tendency to do. Optimus knows this will happen. He spends most of the episode watching the chaos. This comes back in sequel series Beast Machines, after Megatron reformats him into Tankor. It seems he's learned this time, however, since he has a contingency plan in case Tankor turns traitor.
Starscream possessed Waspinator and takes Blackarachnia to be his protege to be the best lying, cheating, backstabbing bastard she can be. It doesn't end well:
Code Lyoko: Almost happened in "Hot Shower". XANA's plan (using a satellite to alter the path of a comet, in order to use it to destroy the academy and the factory) almost ended up like this; the only way to prevent it was for Aelita to devirtualize herself and to put herself in mortal danger. XANA aborted its plan and destroyed the comet, as it needed Aelita alive.
Codename: Kids Next Door: When Rainbow Monkey Corporation scientists tried to make a Rainbow Monkey that looked like them, it became a nerdy-looking plush toy no child from test groups wanted to hug. They were so ashamed of making such a monkey they sent it to space.
In "Operation HUGS", Numbuh 4 was banished to Rainbow Monkey Island to learn how to like Rainbow Monkeys. There, he meets the giant gorilla-like Rainbow Monkey Kong, who like all Rainbow Monkeys is very childish, immature, and huggable despite its monstrous appearance. Numbuh 4 is greatly annoyed by this so he teaches the Kong how to act like a real monster and be dangerous. Thanks to Numbuh 4, the Rainbow Monkey Kong becomes so ferocious and threatening that it goes on a berserk rampage all over the city and attacks the Sector V treehouse.
Also Father's delightfulization of Sector Z. He even lampshades the trope by name when describing what happened, though he seemed quite pleased with the end result regardless.
Bernie takes Corneil to an animal intelligence test building, after Corneil ends with average scores for two tests, he decides to rush through the third test and arrives at a perfect score. Unfortunately, the scientist reviewing Corneil's results claims he performed so admirably his intellect level would be high enough allowing him to talk, forcing Corneil to sabotage the machine to hide his secret.
In one episode, Bernie asks Corneil to dress up as an alien to terrify Romeo, later he gets to Corneil to perform in front of everyone at the school. Romeo and a handful of students then try to catch him, and Men in Black show up to apprehend Bernie for questioning on how he was able to understand the "alien".
In "Dexter's Assistant," Dexter needed an assistant to help him in his newest invention for a science fair. So he took Dee Dee and replaced her brain (which was the size of chewing gum) and replaced it with a new one that made her smarter. Now Dee Dee is much smarter than Dexter was, and knew more about his invention than he did, later when she left Dexter, she won the science fair with her own invention.
In "The Way of the Dee-Dee," Dee Dee spends the entire episode teaching Dexter to loosen up and have fun, which ends with him going on a destructive rampage in his own lab with psychotic glee. She runs out of the lab crying after apologizing to Dexter.
In the Dynomutt, Dog Wondercrossover "Dyno-Might", Dexter becomes convinced that Dynomutt is too much of a goofy idiot sidekick to be any help to Blue Falcon, so he decides to design a new "Dynomutt X-90" to replace him. Unfortunately, Dynomutt X-90 believes that All Crimes Are Equal and uses lethal force to deal with even minor crimes such as littering and jaywalking, forcing Dexter to team up with Blue Falcon and the real Dynomutt to take him down.
This happened to Dexter a lot. Another episode had him creating a robotic assistant with the intention of it raising the efficiency of his lab and overall productivity. Unfortunately, observing Dexter's need for sleep and nourishment as ineffective when compared to itself, the robot proceeded to take over the lab, improving on its design and ultimately rendering its creator obsolete (and thus needing to be removed). In a bit of a Take That! towards Dexter's own single-mindedness, Deedee ultimately destroys the robot via logicbomb because she can't tell the difference between it and her brother.
In the episode "Where No Duck Has Gone Before", To increase the budget for Courage of the Cosmos as part of a way of reinventing it, Scrooge has Gyro build a new spaceship that he wants to be as realistic as possible. Gyro's response? Make it an actual working spaceship.
In the episode "Allowance Day", the nephews want to buy a scooter on sale, but the deal ends one day before they get their allowance, so they pull tricks like recording TV shows and changing the date on the newspaper to fool their uncle into thinking it's Saturday instead of Friday. Their plan works so well that they get their allowance, but the entire world ends up believing it's Saturday, and that includes the store owner, who ends the sale of the scooter that very day. This is, of course, far from the worst consequence of their scheme, which ends up almost getting their uncle killed. Interestingly enough, an episode of TaleSpin has the exact same plot.
Not an experiment per se, but in one of the Earthworm Jim side stories, Bob the Killer Goldfish is trying to get his fish minions to wreak havoc, unfortunately, his minions are, well, fish. A fashion designer stumbles upon this and offers his services to help inspire them to havoc. After several failed attempts with Bob humiliating himself with stupid outfits, he orders his cat minion to wallop the pretentious fashion guy as a demonstration. Now knowing how he wants them to wreak havoc, one of the fish minions proceeds to wallop Bob.
Another one by Bob. The fish on Bob's planet are too stupid so Bob decides to make them much smarter...only with their new intelligence they realize he's a tyrant and overthrow him.
Yet another one by Bob; in one episode he builds a machine that causes him to "evolve" into higher life forms. The last time he uses it, it turns him from a humanoid with an immense brain back into his regular form, because "fish are the highest life form". Bob's not very good with this.
In one episode, Timmy wishes he could babysit Vicky. It goes so well it makes her even more miserable than he is, thus Cosmo and Wanda are reassigned to her.
In the movie School's Out! The Musical, the parents of Dimmsdale send their children to an educational summer camp much to their dissatisfaction, so Timmy wishes kids ruled the world so they can do whatever they want. However, this wish works too good — because children are the dominant life species instead of adults and seniors, the earth is such a fun place to live and no one on earth is miserable anymore, thus all the fairies are pulled back to fairy world and pixies take their place (which is what they planned in the first place).
"I Am Peter, Hear Me Roar" has Peter make sexually inappropriate jokes to a female co-worker and to avoid being fired from his job and getting sued, Peter is forced to learn how to be more sensitive towards women. It takes Peter to being forced to attend a women's retreat camp to understand how women feel. Several weeks later, Peter is no longer insensitive towards women, but his demeanor has changed to become a woman's (even to the point where Peter thinks he has breast cancer and is upset that he can't get pregnant). This upsets Lois because Peter is too caught up in his own feelings instead of tending to Lois' feelings. Things return to normal when Lois gets into a fight with another woman, which gets Peter aroused and drags Lois home to have sex, thus returning Peter to his misogynist self.
"The Cleveland-Loretta Quagmire" depicts Cleveland's wife Loretta cheating on him with Quagmire, with Cleveland, in his typical mild-mannered way, simply takes in stride. Peter, hoping to stop him from bottling up his emotions and give him a "revenge lay," attempts to get him to express how he really feels, but when he goes so far as to act out Loretta and Quagmire's affair with an unwilling Brian right in front of him, Cleveland unexpectedly snaps and vows to kill Quagmire, leading Peter to a rare My God, What Have I Done? moment.
"Death is a Bitch" has Peter, worried he has cancer, checked out by the doctor. The doctor confirms Peter is healthy, then gives him a very large bill. Peter writes "deceased" on the bill, to avoid paying. He doesn't have to pay the bill, but Death turns up to collect him, since after all, he is deceased. Oops.
The episode "Boy (Dog) Meets Girl (Dog)" has a double-whammy. When Peter and Lois fail to convince Chris that Arthur Valentine, a Santa-like character they invented to cheer him up as a kid, isn't actually real, they try get him to stop believing by witnessing Arthur's "death" (by Lois running over a dummy with her car). However, they only succeed in mentally destroying him, so they try to snap him out of it by having Peter dress up as "Arthur" and make it appear that he had come back to life. The plan works, but Chris now believes that "Arthur" has become a zombie and tries to kill him.
Parodied with Project Satan, an attempt to create a sentient car using parts from the most evil cars in history (precisely why they did that is a mystery). It worked, unfortunately. The car was sentient, and indeed, almost giftedly intelligent, but pure evil (the first thing it did was kill the scientists who created it).
The Planet Express Ship is secured with an Unbreakable Diamond Tether. Although it didn't do a very good job securing the ship, it did prove to work as advertised in the sense that it was unbreakable, dragging the whole building along with the ship. They also used it as a fishing line once. They caught a leviathan of some sort, and it dragged the whole ship to the bottom of the sea.
In "Benderama", Bender attempted to use Professor Farnsworth's fun-size duplicator to duplicate himself to do a menial task for the Professor. The two duplicate Benders were just as lazy as Bender, and just as smart, coming up with the same solution, ad infinitum until a Grey Goo scenario began.
Xanatos has Sevarius create Thailog, an evil clone of Goliath, because he wants an ally with all of Goliath's power, but shares his own profit-oriented worldview. It doesn't take long before Thailog decides he'd rather be running the show himself. This exchange sums it up quite well:
Owen: You mean that creature is still out there; it has the money, it's as powerful as Goliath...and it's smarter than you?
Xanatos: Owen, I think I created a monster.
Demona and the Captain of the Guard plotted to allow the Vikings to take the occupants of Castle Wyvern hostage so the Gargoyles could take control of Castle Wyvern. Getting Castle Wyvern captured worked like a bell, all right — and then the Vikings smashed every gargoyle they could find while the sun was still up and they were all still stone. Only by pure dumb luck were Goliath and the five other gargoyles of the main cast not present on the castle walls to be smashed as well.
Demona has a track record of this that spans centuries as City of Stone reveals. She tries to get vengeance, makes a deal with someone to enact said plan which requires betraying someone, the plan works and in the process someone she cares for gets hurt or killed, Demona gets angry, seeks vengeance, etc. Goliath even points it out that it's not working. The message doesn't stick with her however.
Goof Troop: In "The Good, the Bad and the Goofy", Pete makes up a sob story about him being broke and poverty-stricken in order into trick his kidnappers into taking pity on him letting him and Goofy go. The thugs actually buy it, but it also fools Goofy, who accidentally ruins his plan with his big mouth.
Goofy: Gawrsh, Pete, I never knew, seeing as you got giant, big house, and that boat, and that fancy car. I never woulda thought you needed money!
In the episode "Double Dipper", Dipper uses a magic copy machine to create a small army of clones to enact a highlyconvoluted plan to get a dance with Wendy at a party. Problem was, while the clones were setting things up, he and Wendy end up hitting it off by just talking, causing Dipper to realize that he doesn't need a plan, but to just be up-front. The Dipper clones, however, insist on using the plan, and so they lock Dipper in the closet, to keep him from screwing it up.
Another example occurs in the episode "A Tale of Two Stans": Stanford "Ford" Pines thought that the anomalies in Gravity Falls were the result of an alternate dimension that was spilling into theirs. He built the portal to explore it and during the test his assistant Fiddleford. H. McGucket gets sucked into the portal headfirst and emerges a little insane. He never says what he saw, but he was so haunted by it that he employs an extremely literal version of Laser-Guided Amnesia.
An episode of Gummi Bears has Zummi turn Cavin into an ogre so he can infiltrate Duke Igthorn's army, with the caveat that the transformation will be permanent if he's not changed back within 24 hours. Unfortunately for him, his accidental successes are mistaken for competence by Igthorn and he's picked to lead the assault on Dunwyn Castle. Things escalate ("Can't I do anything wrong?") until Cavin is forced to abduct King Gregor himself in order to save him from Igthorn's forces, leading the Gummis to fear that Zummi's transformation spell has left even Cavin thinking he's an ogre.
Hey Arnold!: In "Arnold's Halloween", Arnold and Gerald pull a prank at Grandpa Phil's Halloween party by using an old transmitter to broadcast a fake news bulletin about an alien invasion over the radio. Other touches to the prank include disguising the city's water tower as an alien mothership and inviting Helga and her friends, who are trick-or-treating as aliens, to show up at the boarding house. However, their signal gets picked up by an associate of Douglas Kane, the paranoid host of UFO Tonight, who also gets video footage of the "aliens", and Stinky's electrical hookup for the "mothership" causes a citywide blackout. As a result, the news of an "alien attack" sends the city into chaos, and Helga and the others end up getting chased by an angry mob.
In an episode, the normally ineffective robot GIR gets locked into "duty mode", which makes him actually competent. He quickly (and accurately) decides that the biggest obstacle to the Irken takeover of Earth is, in fact, Zim himself...
"Bad Bad Rubber Piggy" has Zim using temporal interference via toy rubber pigs to kill Dib by causing accidents to happen in his past. It works perfectly, and Dib dies... and then his father revives him in titanium mecha suit. Every attempt at interfering after that just causes the suit to get upgrades. Zim only manages to survive the episode by using his final rubber pig to write a message to himself, telling him not to use the time portal, thus hitting the Reset Button. Unfortunately, Zim only managed to stop himself because after the rubber pig was sent back, it ended up replacing his brain in the process, leaving him a mindless idiot.
Also occurs in the Christmas episode, when Zim's Santa suit starts taking him over and forcing him to act like a real Santa.
Zim: I designed the suit too well... 'cause I'm amazing.
Parodied in another episode, in which Zim is captured by a pair of dumb aliens (known only as Blue and Green) who intend to perform "hideous experiments" on him. They begin by fusing him with another human being, a process that involves nothing more than taping a gopher to his head. As the aliens debate on whether or not to "fuse" him with a juice carton they have at hand, Zim makes his escape, causing the aliens to reflect on their experimentation.
Blue: We shouldn't've fused him, we made him twice as powerful! TWICE AS DEADLY!!
Green: I tell you, that juice would've slowed him down for good!
Jellystone!: "My Doggie Dave," Doggie Daddy can't handle being away from his daughter for more than a few seconds, so he and Augie create "Dave" to join on grown-up nights out. "Dave" ends up being so popular, Augie gets invited out for numerous other functions, leaving Doggie Daddy completely alone.
In the episode "Legends", a young man, mentally scarred and mutated by a nuclear holocaust which destroyed his world and his super heroes The Justice Guild, used his new powers to recreate that idealistic society, forcing any who survived to be trapped in his fantasy or else... Eventually the Guild discovers they are just figments of his mind and have a choice: allow his tyranny to continue and they themselves will live, or fight him and die for the world once more. They choose to be the heroes he imagined them to be, and die for the world once more.
"Let Justice Prevail!"
In the episode "Hereafter", Superman is sent to the future, where he discovers that Vandal Savage has succeeded in taking over the world. However, he accidentally wiped out all of humanity in the process. Being the ruler of a planet with nobody else on it has left the immortal man quite bored and immensely regretful of his actions. He built a spaceship and can leave Earth whenever he wants, but he chooses to stay on the planet he ruined in self-imposed exile to punish himself for his screw-up. He even helps Superman return to his own time for the purposes of stopping him.
In one episode, Stumpy enlists the help of Quack Quack and Mr. Cat, as well as Kaeloo since she's an actual girl, to show him how to impress a girl. They decide to pretend that he is the girl and show him how to act. Kaeloo and Mr. Cat fail horribly, but Quack Quack does a good job. Such a good job that Stumpy winds up falling in love with him and chases him around.
Drakken's Bee Bee robots in Kim Possible. He built them to be perfect — which made them realize they shouldn't have to obey him because he wasn't perfect.
In one episode of King of the Hill, Hank starts working with people in a co-op so he can take advantage of the high-quality steaks they offer. While at first the co-op workers are unsure how to run a store, Hank helps them to make the store better, having the end result of making the hippies far more capitalistic and causing them to sell the store to the Mega-Lo-Mart, which Hank was trying to avoid.
In an episode of The Land Before Time TV series, Littlefoot and Cera meet a new friend of Ali's named Rhett, who is a total braggart making up stories of how he saved his herd from Sharpteeth, which convinced Ali. To expose Rhett's lies, the Gang come up with a scheme in which Chomper pretends to be a vicious Sharptooth and scares away Rhett. The scheme works, but then Rhett comes back with an angry mob of Longnecks that chase Chomper, believing him to be a genuine threat that must be exterminated.
Legion of Super-Heroes: Imperiex, the Big Bad of Season 2, wants Brainiac 5 to join forces with him; in order to corrupt him, he manipulates him into accessing and using the programming of the original, evil Brainiac. Shortly thereafter, Imperiex is a scattering of pixels and the show has a brand new Big Bad.
The final scene in the animated short "Ready, Set, Zoom!" has Wile E. Coyote donning a female road runner costume to attract his prey. Unfortunately, there's about a hundred starving coyotes waiting behind those rocks.
Another short ends up with the Coyote chasing the Road Runner through a series of smaller and smaller pipes, both ending up shrunken to the size of a bug. They both chase back into the pipe, the Road Runner returning to original height, while the Coyote remains shrunken. At first oblivious to this development, the Coyote jumps and grabs a hold of the Road Runner's leg. Then, after he looks in horror up at the gigantic Road Runner, looks to the audience while holding a sign saying "... you always wanted me to catch him... now what do I do?!?"
Typically, whenever one of the Acme Productsdoes work as advertised, their success manages to work against Wile E. rather than for him. For example, a Dehydrated Boulder, upon hydration, becomes so large that it squashes him, the Burmese tiger trap catches an actual Burmese tiger (in the North American desert?), or he finds out that the Earthquake Pills bottle label's fine print states that the pills arent effective on road runners... right after he swallows the whole bottle thinking they don't work.
In the short "Rebel Rabbit," Bugs is offended that the bounty on rabbits is a mere two cents, compared to foxes and bears (who possess $50 and $75 bounties, respectively), on the ground that rabbits are "perfectly harmless" compared to them, and sets out to prove that rabbits can be just as bad, becoming a Person of Mass Destruction by, among other things, selling Manhattan Island back to the Native Americans, filling in the Grand Canyon, and sawing the entire state of Florida off from the rest of the country. The end result: a bounty of one million dollars is placed on Bugs' head, and is hunted down by the entire US Army, who lock him up in Alcatraz:
Bugs:(as he's surrounded by artillery shells in a foxhole) Ehhh, could it be that I carried this thing too far? (the shells explode; fade to Bugs in a cell in Alcatraz) Ehhh, could be.
It once happened even in a show Pepe wasn't supposed to be part of. In the Tweety and Sylvester short "Dog Pounded", Sylvester disguised himself as a skunk to scare away some dogs from a dog pound where Tweety was. It worked... until Pepe appeared out of nowhere.
Also one episode had Pepe trying as he might, as he does, to woo a "skunk". The two fall in a rain barrel and the paint gets washed off the cat's back, Pepe apologizes for soaking her, and walks away. The cat gets a glimpse of Pepe's surprisingly broad shoulders and firm physique and starts chasing him. It's what he wanted, of course, except there's nothing attractive about a wet cat. Sauce for the goose is sauce for the gander, Pepe!
In "No Guts, No Glori", Mom and Dad go out on a date and leave Lori in charge, which annoys the siblings as she takes the fun away from her. So, Lincoln rallies them up to lock Lori in her room and leave Lincoln himself in charge. However, when he allows his siblings to have fun, they suddenly enjoy themselves so much they trash the whole place and decides to recruit Lori to get them under control again.
In "Yes Man", Lincoln teaches his sisters how to butter up their parents to give them money for the things they want. His advice works for them, but the next time Lincoln tries to get money from his parents, they won't give him any because they gave it all to the girls.
In "Tricked!", Lincoln and Clyde encounter a pair of bullies while looking for a perfect place to trick-or-treat and Lincoln, not wanting them to know about their destination, convinces them that Franklin Avenue, his own street, is the ideal place to get candy. But when they get back home, they discover that the duo had wreaked havoc on the neighborhood and stole everybody's candy.
In "Future Tense", new neighbours inspire Lynn Sr. and Rita to bring their kids to their full potential by enrolling them in classes and clubs to improve upon their shortcomings and have them take up community services. When the kids meet the parents' expectations, they want to do fun activities like eat ice cream or watch a movie, but the kids don't find them fun, considering them ineffectual for their well-rounded activities. Realizing they've gone too far, the parents apologize to the kids and decide to worry about their future later.
Miraculous Ladybug: In a Bad Future shown in the episode "Cat Blanc", Hawk Moth succeeds in akumatizing Cat Noir and killing Ladybug. Unfortunately for him, the mentally unstable Cat Blanc proceeded to unleash an Angst Nuke that killed Hawk Moth along with the rest of Paris.
Early seasons have a pattern of Twilight Sparkle's spells working a bit too well for her own good:
In "Swarm of the Century", she casts a spell to stop the swarm of parasprites from eating all the food in Ponyville. And it works — the parasprites start eating everything except the food.
Played with in "The Best Night Ever". Princess Celestia invited Twilight Sparkle and her friends to the Grand Galloping Gala to liven it up. They end up being so lively that the party is destroyed. The thing is, Celestia still considers her plan Going Horribly Right an improvement over what the Gala would have been like without their interference.
Twilight's "Want-it-Need-it" spell, seen in "Lesson Zero". She uses it to create an Artifact of Attraction to cause a conflict that she can "solve". It works all too well when all of Ponyville is dragged into the mess.
Yet another of Twilight's spells messes up in "Bats!" Twilight's plan to use Fluttershy's Stare to stun the bats and stop them from eating all the apples works, but it turns Fluttershy into a vampire bat/pony hybrid.
In "The Cutie Pox", Apple Bloom whips up a magic potion to give herself a Cutie Mark. It works, but then she gets a second cutie mark, and then another, and before long she's got a bunch of cutie marks and finds herself compulsively performing the talents that go with them.
As the Cutie Mark Crusaders find out the hard way in "Hearts and Hooves Day", the "love potion" they made from a recipe in a storybook was more of a "love poison". The prince and princess who took the potion in the story could do nothing but stare into each others' eyes while their kingdom was falling apart. Unfortunately, they only notice this after they've given the stuff to Cheerilee and Big McIntosh, who they barely manage to save from a similar fate.
In "The Cutie Re-Mark", Starlight Glimmer returns, armed with a Time Travel spell that'll let her go back through time perfectly, with the plan to stop Rainbow Dash's first Sonic Rainboom as revenge for the Mane Six ruining Our Town. Each attempt ends up bringing a Bad Future to Equestria and Twilight has to drag her kicking and screaming to the worst of the bunch — a barren wasteland — to get her to see what she's doing.
In "Frenemies", Grogar (actually Discord in disguise) sends Tirek, Chrysalis, and Cozy Glow on a mission to become allies and learn to work together without constantly bickering with one another. This works quite well — in fact, they almost become friends and decide to unite to plot against him.
Phineas and Ferb: In "Phineas and Ferb's Quantum Boogaloo", adult Candace finally busts her brothers after going back in time... only to see how bad are the consequences after she returns to her present. She was expecting the boys would just get grounded for building a homemade rollercoaster, but her actions lead not only to enraged parents banning creativity for children, but also to Doofenshmirtz taking over the Tri-State Area because Candace inadvertently foiled one of Perry's plans to stop him. Thankfully, she manages to undo the Bad Future.
Recess: School's Out has Prickly getting the Superintendent to stop Phillium Benedict because he was threatening to cancel recess. It works too well: although he did certainly stop Benedict from cancelling recess, he also unintentionally got Benedict's job instead, with Benedict being demoted, earning bitter enmity from Benedict.
In one episode where everyone besides TJ and his friends got sick as a result of food poisoning from fish tacos served by the cafeteria cooks, TJ and his friends try to fake sick after being sick (no pun intended) of being the only students at the school, and Gretchen has them use blue tongues and green spots to achieve the perfect way to fake sick to the nurse. It worked. Unfortunately, it worked a bit too well for them, as the sickness that Gretchen chose was actually a biohazard kind of illness that resulted in them being put in quarantine well past when all the other students got better.
In the episode The Library Kid, the gang introduces the titular fourth grader to the playground, trying to get her to experience something other than books. Unfortunately, the same obsessive personality that made her a 24/7 bookworm causes her to become so obsessed with recess that she performs incredibly dangerous stunts on the playground and won't stop.
Played for Laughs in one episode. Couple's Corral, an online dating site, works pretty well, even leading Mordecai to new friend (and later girlfriend), C.J. The problem, as explained by its CEO, it that is worked so well that there weren't any lonely singles left to subscribe.
In another episode, Rigby decides to change his name to "Trash Boat" to gain admiration. This causes everyone in the city to laugh at him with ridicule for his new name, until a washed-up rock star from the future appears and explains to Rigby that his name-change made him such a laughingstock he did become a celebrity just as he wanted, but now has arrived to kill Rigby so that he get back the fame Rigby took from him.
The Replacements: Many of the earlier episodes were pretty much built around this trope.
"Todd Strikes Out": The kids' baseball coach (who uses the stock Aesop "It's not whether you win or lose, it's how you play the game" to excuse his absolute incompetence) is replaced with a major league player (who puts the kids through a brutal training regimen).
"The Jerky Girls": The Happy Hornet troop leader (whose overzealous interpretation of their rules makes it impossible for the girls to sell any of their jerky) is replaced with a con man.
"Skate-Gate": The town's mayor (who bans skateboarding on public property, and then demolishes the town's skate park For the Evulz) is replaced with a professional skateboarder (who basically turns the entire town into one big skate park).
"Zoo or False?": The local zoo's keeper (who has absolutely no concern for the animals' quality of life) is replaced with an animal rights activist (who, after being denied the funds for her desired changes, lets all the animals run free).
In the Scooby-Doo, Where Are You! episode "Go Away Ghost Ship," the gang goes out on a speedboat and use a recorded foghorn to pose as the freighter that Redbeard's ghost is after. Their plan works all too well, and Redbeard's ship rams their speedboat and splits it clean in two.
In Season 2, Catra uses the First One virus from "System Failure" to infect Adora in order to nullify her She-Ra form. To be fair, it definitely does end up nullifying the She-Ra form. Unfortunately for Catra, however, the virus had two other properties she neglected to consider. First, before nullifying Adora's transformation, the virus turns her into The Berserker, leading to Catra having to run for her life from an Adora who is completely uninterested in holding back like she usually does. Second, the virus also infects a bunch of First One robots, one of which is only prevented from killing Catra by Scorpia destroying the artefact that controls the virus.
In Season 3, Adora attempts to snap Catra out of the Lotus-Eater Machine they're in and restore her true memories. On the bright side, it works! On the less-bright side, Catra's true memories contain the wildly out of control emotional issues that led to her making the astonishingly terrible decisions that landed everyone in the Lotus-Eater Machine to begin with.
In "Hurricane Neddy", Flanders suddenly erupts in a violent, angry rant at all his friends and neighbors for trying (albeit completely incompetently) to help him after his house was destroyed. After having himself committed we learn by flashback that his usually overly-friendly personality came as a result of an experimental psychological treatment he had as a child, back when he was so badly behaved and his parents, being beatnik stereotypes, wouldn't actually do anything. "Yeah Doc, we've tried nothing and we're all out of ideas!" The end of the episode also hinted that Ned's therapy afterward might have resulted in this too (before Flanderization kicked in).
Ned: And if you really tick me off, I might run ya over with my car!
Also parodied in the episode "That 90s Show". Homer visited Moe's Tavern back when it was a cigar bar in the 1990s while in a slump. When Barney ended up forcibly exhaling a huge plume of smoke from smoking his cigar a bit too fast, Moe attempted to use this as an opportunity to steal a watch from one of his customers. However, he couldn't get it off in time before the smoke dissipated. Moe, in order to evade a potential telling off/beating, tried to come up with the alibi that he was "coming on" to the customer. Turns out the customer was actually gay, and he said "okay, you can stay at my place.", meaning that his alibi to get him out of trouble worked too well as he was most likely inviting him over for gay sex. Cue Moe saying "Oh, boy." with a squicked expression.
In "Mother Simpson", Homer fakes his death with a dummy so he could get out of a community service project held by Mr. Burns so he could spend time with his family. It worked, all right. Unfortunately, it also led to the rest of Springfield also believing that Homer had indeed died, that lasted until the Simpson house's power was cut due to it being registered in Homer's name, resulting in Homer clearing up the "Misunderstanding" after Marge forced him to.
In "Homer the Smithers", Mr. Burns forces Mr. Smithers to take a vacation. Since Smithers likes his job and wants to avoid having this happen again, he looks for the most incompetent person possible to take his place, so naturally he picks Homer. This turns out to work all too well, as Homer is so terrifyingly incompetent that he scares Burns into learning to take care of himself, so after Smithers comes back, Burns no longer needs an assistant and thus fires him.
Milder example in "Itchy & Scratchy & Marge". Marge protests against the Itchy and Scratchy cartoons as setting bad examples for impressionable small children. Once she succeeds in convincing the company to eliminate violence on said cartoons literally turning it educational, not only did the smaller kids learn to do positive things, the older children hated the new version of the cartoon so much that it resulted in all of the older kids of the neighborhood temporarily no longer watching television preferring the outdoors with having the enjoyment of mostly positive outdoors activities. Marge pleasantly admits it wasn't what she expected.
In "Flaming Moe's," Bart prank-calls Moe's bar, which has become a high-class, upscale establishment due to the fame Moe has earned from stealing Homer's homemade recipe. Bart asks to talk to someone named "Hugh Jass"...only it turns out there actually is a customer there named Hugh Jass.
In "Lemon of Troy", Marge attempts to instill a sense of town pride in Bart to stop him from vandalizing property. However, her lesson causes Bart to develop xenophobia for other towns, which leads him to rope his friends into a dangerous quest to take back Springfield's lemon tree from Shelbyville.
In "The Old Man And The Lisa", Mr. Burns loses his wealth but regains it when Lisa teaches him about recycling, leading him to develop his own recycling plant which features "the Burns omni-net", a fishing net made of old six-pack rings that sweeps the ocean, turning the local sealife into an all-purpose slurry, to Lisa's horror.
In The Smurfs fourth season opener, "Symbols of Wisdom", Brainy Smurf and Gargamel decide independently to grow beards, thinking that wisdom comes from having a beard. Gargamel's magic hair tonic gives him such a long, thick and tough beard that it traps him inside his hovel. After Papa Smurf frees Gargamel, he and the other Smurfs discover that Brainy is in a similar predicament.
The creators of Walmart sought to establish the ultimate convenience store chain, and ended up creating an all-consuming monstrosity that feeds on greed and rampant consumerism, enslaves the minds of its customers and employers, and brings misery and degradation to any settlements where it sets roots... We're still talking about the cartoon, right?
In "Tweek x Craig", the eponymous couple are Mistaken for Gay and decide to stage a fake break-up to put an end to it. When Tweek protests that he's a terrible actor, Craig advises him to just "follow [his] lead and try and make it believable". Turns out Tweek is actually a far better actor than he gave himself credit for, and he gets caught up in the act and unintentionally makes Craig out to be a manipulative cheater.
In "The Damned", Hillary Clinton's campaign managers train her to say "My opponent is a liar and should not be trusted" to anything Mr. Garrison says. However, they didn't expect Garrison to try to throw his campaign and say that Clinton is better off running the country than him, which proves detrimental to both campaigns.
In "Texas", SpongeBob and Patrick mock Texas in front of Sandy so she can chase them and lure her to a party they're throwing for her. It's only afterward that they realize they've triggered Unstoppable Rage in Sandy and they now have to run for their lives.
In "Squilliam Returns", Squidward tells SpongeBob to "empty his mind" of anything that isn't about fine dining (and breathing). He does just that, and ends up forgetting his own name as a result.
In the episode "Mrs. Puff, You're Fired," Mrs. Puff is replaced as boating school teacher by a Drill Sergeant Nasty, who puts SpongeBob through Training from Hell to correct his Drives Like Crazy tendencies. Unfortunately, as a result of the new teacher's harsh drills and very specific teaching methods, SpongeBob can only drive correctly while blindfolded, and since he's legally forbidden to drive blindfolded, his boating test with the new guy fails as usual.
In "Fear of a Krabby Patty", Plankton opens the Chum Bucket for 23 hours to manipulate Mr. Krabs into opening the Krusty Krab 24/7, so SpongeBob will eventually wear out to the point he has to hand him the formula. Well, not only is the sponge worn out after 43 days nonstop, he is somehow afraid of krabby patties.
In "Shellback Shenanigans", Plankton disguises himself as Gary to get into the Krusty Krab's "Bring Your Pet To Work Day" in his latest attempt to steal the secret formula. However, the plan works so good that not only is SpongeBob fooled, but the sight of "Gary" "turning green" and "talking" makes him think something's wrong, and sends him to the hospital where he believes he's terminally ill.
In "Bumper to Bumper", Mrs. Puff comes up with a solution to help SpongeBob with his driving freak-outs, by having him repeat to himself, "Focus on the road, there is nothing but the road." He repeats the advice, and drives perfectly... unfortunately, it works too good, as he's now too focused on the road that he cannot park, and once they're off the road, he starts to panic.
Star Wars Rebels has a two-parter with Kanan teaching Ezra to open himself to the Force. He finally succeeds...and then gets a lot more than he bargained for when Ezra's fear and anger get the better of him and he gets his first taste of the Dark Side.
In "School Spirit", Star misunderstands when Marco tells her the football team is going to be "slaughtered" by their rivals (he just meant horribly defeated in the game). She booby traps the field, but when she learns the truth and all the traps start going off... well, the quote at the top of this page says it all.
In "Cheer Up Star", Marco tries to lift Star's spirit by luring some monsters she can fight. He ends up bringing more than he wanted to.
In "Hungry Larry", Star and Janna summon a monster named Hungry Larry to make Mr. Diaz's haunted house scarier. He does make things scarier, in the worst kind of way.
According to The Magic Book of Spells, there was originally a fifth member of the Magic High Commission, a humorless giraffe-man named Reynaldo the Bald Pate. When Star's ancestor Rhina the Riddled tried to cast a spell on Reynaldo to get him to appreciate her riddles a bit more, it worked a little too well and compelled him to speak only in riddles, which resulted in him stepping down from the MHC.
Rhina later decides to get back at her abusive husband via a spell to cause a broken heart. The spell literally breaks his heart, causing him to instantly die of a heart attack. And since her husband's cousin was the king of the Underworld, this also strained the alliance between the Butterfly and Lucitor kingdoms.
In the episode "Cat Fingers", Steven learns from Amethyst how to use his natural shapeshifting ability and uses it to turns his fingers into miniature cats. In the process of trying to get rid of them, they end up growing all over his body and he has to get help from his muggle dad to solve the problem.
Peridot was conditioned by her superiors The Diamond Authority to be dictated by logic and reason, so she eventually came to the conclusion that letting the Cluster destroy Earth would be illogical and promptly jumped ship.
The Zircon Lawyer assigned to defend Steven (aka "Rose Quartz") in a trial before the Diamonds. Despite her inital worries, she's able to make a solid case after realizing the only reason a trial would even be occurring in the first place is because the Diamonds don't know what happened when Rose allegedly killed Pink Diamond either. She follows this line of reasoning to conclude that circumstances wouldn't have allowed Rose to kill Pink even if she wanted to, and that only another Diamond could have shattered Pink. Yellow Diamond is so upset by the accusation that she poofs the Zircon, though she ultimately does live.
In "Kevin Party", Kevin convinces Steven to bait Connie into making the first move in them reconciling with each other by giving her the cold shoulder treatment and pretending that he's doing great with her gone from his life. While the tactic does get the two to communicate with each other, Steven makes himself look so happy and content that it causes Connie to believe he's decided to cut her out of his life forever and move on with a new crowd of friends, sadly wishing him well after explaining the past month was a case of major miscommunication, and almost leaving the party in resignation of their broken friendship before Steven stops her.
Pink Diamond faking her death. She rightfully assumed that the act would result in the other Diamonds deeming Earth a lost cause and ending the war. The problem is that she's terrible with emotions and didn't realize they would grieve her death, which would lead to their method of ending the war not just being to withdraw most of their troops, but also hit the planet with a Fantastic Nuke to avenge their lost family member.
TaleSpin: In the pilot movie "Plunder and Lightning", Kit tries to help his friends escape from Don Karnage by pretending to take a level in jerkass and join the sky pirates. However, this apparent double-cross makes Baloo so angry, that he quits Higher for Hire and leaves Kit behind with the pirates.
Mr. Paulson from Teamo Supremo considers the Mega Gauntlets his greatest mistake because he built a weapon he deemed too powerful. They would prove to be trouble when his assistant Crawford stole them and became a supervillain.
Tiny Toon Adventures: In one cartoon, Buster and Babs help a trio of unemployed black and white cartoon characters who haven't worked for decades and have been forced to sell their cartoon effects reclaim their fame. Buster and Babs succeed and end up creating a new show that could put THEM out of work.
Wishfart: Some wishes that Dez has granted have this result. One memorable instance is when Akiko wishes to become the most terrifying ghost ever in order to impress her parents. She becomes a raging Onryo with Black Eyes of Evil, horrifying Dez and Puffin and causing a great deal of havoc around their apartment.
In X-Men, the fully sentient Master Mold is created to more effectively command Dr. Trask's Sentinel robots in their mission to "protect humans from mutants." Master Mold concludes that this requires the Sentinels to take over the world and strictly control the human population.
Trask: You can't make me do this! You were designed to protect humans from mutants! Master Mold: That is not logical. Mutants are human. Therefore, humans must be protected from themselves.
This hits the Young Justice version of Dr T.O. Morrow as well — coming and going. First his attempts to create 'heroic' androids to infiltrate the superhero community and destroy them from within fail due to his creations being too heroic and sacrificing themselves or turning on him outright. Infuriated by this, he decides to create a final perfect android without any such moral inhibitions... who of course immediately turns on him and rips him apart.