Avengers, Assemble! is often accused of relying too much on idiocy to make the plots move forward. The series attempted to duplicate the Teeth-Clenched Teamwork attitudes of West Coast Avengers, but for the most part, it resulted in a bunch of characters who spent far more time arguing with each other while the villain continued their plans in the background.
Beavis and Butt-Head intentionally invokes this trope to its logical extreme. The entire point of the show is watching the two dumbest characters in history struggle with mundane tasks. If either character had a single shred of intelligence, it wouldn't be nearly as funny. However, every other character in the show, except maybe Daria, also seem completely incapable of recognizing that B&B are just complete idiots as well.
The main characters of Da Boom Crew are trapped in a game they coded, and yet are continually surprised by what they encounter.
The entirety of The Grim Adventures ofthe Kids Next Door was just one big Idiot Plot that involved all kinds of KND and Billy & Mandy characters falling for some of the most pathetic Paper-Thin Disguises in fictional history. We can expect this thing from those minor Billy & Mandy characters but every single KND moon base operative falls for them too. The only ones without an Idiot Ball attached were Mandy, Grim, Numbuh 5, The DCFDTL, and (most of the time) Numbuh 1. Billy, on the other hand, is an Idiot Ball, so he doesn't count.
As mentioned above, this is standard fare for The Grim Adventures of Billy & Mandy, to the point where few episodes begin without being catalysed by Billy AKA Idiot Ball incarnate and Grim and Mandy stupidly giving in to his demands. For Grim, he's their best friend/slave forever, but one expects better from Only Sane Woman Mandy (though it could be because she enjoys watching Billy in pain).
Even after over 50 years, Scooby, Shaggy, and the rest of the gang still run from every monster they see after so many frauds. Might be justified though, as thefew times they do think it's a hoax, it turns out the monsters are real.
And even if they know it's a hoax, often the monster is dangerous in their own right, but virtually every monster could get taken down if faced by more than a single unarmed cop, so then the question is why they never call authorities against, say, a lone ghost miner.
It should be noted that Scooby-Doo! Mystery Incorporated subverted this to a degree. Many of the monsters were indeed humans in costumes... that weren't exactly afraid to inflict physical violence on the gang. They may be teenage sleuths, but they don't have guns or real means to protect themselves, so keeping a distance and running for their lives were justified. Not to mention the main local law enforcement is a sheriff who (especially in early seasons) sees it as town policy to not investigate or apprehend the monsters until they've been thoroughly proven as hoaxes, since the town is a tourist trap that relies on local legends of monsters to attract people. He could either put in a lot of work to investigate the mystery and shut down a potential revenue stream in the process, or declare it an evil monster, fence off the area, and call it a night.
The various Super Mario Bros. cartoons were often driven by the characters being suddenly weakened to the point where they walk into or can't escape traps that they would have easily dealt with before. Other ridiculous examples include them just standing and watching as Harmless Villain King Koopa tosses Chain Chomps at them, which latch onto their ankles like makeshift manacles and leave them easy to capture.
One Chaotic episode involves Kaz's science teacher receiving scans from the UnderWorlders in exchange for the technology to travel between dimensions. Did he not stop to consider that if Chaotic was invaded, all his scans would be worthless? (It was All Just a Dream though.)
An even more blatant one is the episode where Kaz is in danger of being able to return to Chaotic because his mother will take his scanner away, all because Kaz keeps insisting, time and again, to everybody in his vicinity that Chaotic and Perim are real and he even does his school assignments based on his adventures there, this despite having absolutely no way to prove (except for a Contrived Coincidence at the end of the episode) that these places actually exist.
In the episode "Where Is Thy Sting?," first when Bumblebee and Wasp switched places with none of the other Autobots noticing that Bumblebee (really Wasp) has purple eyes as oppose to his normal blue ones. This was visible even with Bumblebee's battle mask up. Then, Optimus and Ratchet get into a battle with Jetfire and Jetstorm of the Elite Guard which could have been avoided.
The Transformers had many of these, most famously in "A Prime Problem" where Megatron constructs an exact replica of Optimus Prime that he controls via remote, only to have the real Optimus show up, and Teletraan 1 inexplicably is unable to tell them apart when scanning them. Instead of, you know, asking the Primes questions only the real Prime would know or not noticing that the fake Prime mixes up Ironhide and Bumblebee (which given the fact that Megatron has been fighting these guys for millions of years and should freaking know them by now, is another level of stupidity), their solution is to have them race to see who's the fastest. Became a bit of Memetic Mutation in the fandom.
And of course numerous episodes where the Decepticons are shown the ability to create incredible machines that do unworldly things, yet half of the season 1 and 2 episodes revolve around them trying to steal rather mundane human inventions that they, could, you know, probably create themselves without drawing attention.
Nearly every single episode of ThunderCats (1985) relies on the titular characters being as thick as possible. Lion-O, with a firm grip on the Idiot Ball, is a very good example, though since he's a kid in an adult body it's somewhat excusable. Occasional episodes, however, will have him pass it off to the others, usually Tygra who gaily runs with it straight into trouble.
Arthur has had several cases of this over the years; perhaps most notably is the failure of Arthur's parents to discipline D.W. whenever she takes to giving Arthur a hard time or just being the self-entitled brat she frequently is. Most of the time they just blow it off or just grin cluelessly while Arthur endures her antics, even when she embarrasses him in public or in front of his friends. Even when she throws a temper tantrum or is just being obnoxious for the sake of attention, they rarely do act upon her behavior, almost as if her being the younger sibling somehow grants her a free pass.
"Buster Baxter, Cat Saver" sees Buster become an overnight celebrity after rescuing a cat from a tree, and the entire town showers praise upon him just because its overreacting owner called him a hero. Pretty soon all the press and merchandising causes Buster to become conceited, as if the tale of someone fetching a cat out of a tree was so unheard of that it demanded the front page coverage it receives.
Arthur's entire dilemma in "Arthur's Mystery Envelope" rides on Mr. Haney apparently saying nothing about the package he asks Arthur to bring home to his mom, and on Arthur not simply asking what it was. Sure, Arthur and his friends may have overreacted and were too quick to assume the worst like it meant bad news, but they're just kids and simply explaining to Arthur what the deal was would've spared the poor kid his sister's harassment later.
"Locked in the Library!" involves Arthur and Francine both inadvertently falling asleep and ending up locked inside the library after closing time. Apparently the staff don't do a quick head check to make sure everybody has left, so the two of them were utterly screwed when they came to.
D.W. pretends to lose her voice in "For Whom the Bell Tolls" so that she can take advantage of Arthur, and when Arthur catches her in the act and reports it to his mom she makes zero effort to investigate whether this is true or not, instead sticking to D.W.'s story and acting as if D.W. essentially forcing Arthur to be her servant was anything unusual for her.
Nobody in "Play It Again, D.W." seems to take her obsession with listening to Crazy Bus seriously. Even when they are forced to wear ear plugs because of it, they do little to curb her constant disruptions from playing the song too loudly and too constantly, leaving Arthur to endure it even when he's trying to get a little peace and quiet or finish his homework.
Apparently Francine never stops to think that turning in a paper she didn't write could possibly be against the rules in "Francine's Pilfered Paper", despite being one of the smartest members of the gang. Lucky that Catherine pointed out her mistake before it was too late. What makes it even worse is that Mr. Ratburn is somehow fooled into thinking it was her own work; never mind that it doesn't take a genius to tell the difference in quality between a scholarly research article (or if it wasn't that, any sort of paper written by any sort of professional adult) and a third grader's paper.
In "Revenge of the Chip" Mrs. Read tells the city newspaper and the family the story about how D.W. thought she'd die from eating green potato chips, unknowingly causing D.W. major embarrassment even though D.W. had told her family flat out not to repeat the story right in front of her at the start of the episode.
Arthur and the Brain find themselves panicking when in "Arthur and the Very Mean Crossing Guard", the guard in question threatens to go after them if they don't pay to cross the street, and they believe every one of his outlandish claims. And if that weren't bad enough, it turns out at the end that he was only kidding around and didn't mean to actually scare them; however from the way he goes on about it, it sure didn't sound like a joke, making both sides guilty.
"Waiting To Go" is all about Brain and Binky panicking because their parents are late to pick them up from soccer practice, leave them to fend for themselves in the parking lot when the wait turns out to be no more than fifteen minutes; the gang has been seen to walk home just fine without much problem, and their panic is very much out of nowhere.
"Buster Gets Real" is all about Arthur trying to preserve his friendship with Buster who has given up Bionic Bunny in favor of reality shows because he argues that Bionic Bunny is "not real", and thus not worth his time; Arthur fears that they no longer have anything in common as a result of this. Ignoring the fact that Buster is seen watching Bionic Bunny again in episodes that have since followed, someone as imaginative and flighty as Buster rejecting his former interests strictly because it's "not real" comes off as an extremely out of character moment that is made strictly for the sake of this conflict between the two.
The infamous "Arthur's Big Hit" largely rides on the ability or the unwillingness of Arthur's parents to discipline D.W. when she doesn't stop fiddling with Arthur's model plane, or his failing to keep it safe when finished even though she had interrupted his work constantly. Her not realizing a model plane can't fly is understandable, but when she breaks it and the hit is given, Arthur's parents never sufficiently punish D.W. for her part in the incident onscreen, and he seems to be dealt the more severe punishment.
The idiocy however really sets in as Binky, who has no involvement in the affair, is ordered to hit Arthur to prove how tough he is when he and his band overhear what Arthur did. He ultimately goes through with it solely under peer pressure, and this is strictly present to force Arthur to see his own fault, by involving someone who had nothing to do with it.
Part of the reason why some episodes of Foster's Home for Imaginary Friends aren't so fondly remembered is because if they're not overly sadistic and mean-spirited, then they're relying on this trope to make the plot work (as well as also sometimes having the sadism on top of all the idiocy):
The last act of "Duchess of Wails" is a pretty egregious example since everyone whose names aren't Mac, Bloo, Duchess or Terrence suddenly turn into a bunch of giant dumbasses. The episode starts with Duchess getting adopted by a family that turns out to be Mac's new neighbors. Duchess' constant dismay over her new stresses Mac's mom out to the point where she wants to move out. Terrence makes Mac believe that they're moving to Singapore (which he thinks is in Wisconsin) so he teams up with Bloo to vandalize his neighbor's apartment to make them believe Duchess did it so that they can return her to Foster's. When that doesn't work, they just outright kidnap her and return her to Foster's by force. For no explained reason, Terence is somehow able to beat them there despite being slowed down by falling into a pile of wet cement, and tells everybody that they're coming to return Duchess (while purposely leaving out the reason for why). Everybody blindly takes his word and blocks their attempts to get her back in by bombarding them with sharpened carrots and apples among other things. It's only after they've needlessly tortured them that they find out why they were returning her so they take her back... On the condition that Mac & Bloo become Duchess' personal assistants and go through the same suffering that everyone else did at the beginning of the episode. Even worse, Terrence manages to get off scot-free for the whole ordeal besides a couple of angry glares from everybody when they realize they've been tricked.
The whole thing with "Crime After Crime" suddenly suffering from Mood Whiplash in the final act by pointlessly torturing Mac for about two minutes could've been avoided had it not been for this trope. A running gag throughout the episode is that Frankie has to keep making "It" until she gets it right due to the bowl with the "It" in it continuously getting ruined by loose plaster from above falling into the bowl due to people jumping on Madame Foster's bed. The fourth time this happens, it's because of Mac which causes Frankie to come upstairs and forcibly kick him out believing that he's been the one jumping on the bed all day. What follows is about a minute and a half of Mac being chased by the police due to his bag being full of diamonds that Bloo had placed inside in order to try and get out of having to eat the "It" for dinner. All of this pointless cruelty towards Mac could've easily been avoided had Frankie just moved the "It" bowl the first time it was ruined.
On Phineas and Ferb, the incredibly awesome Fireside Girls are trying to raise money to protect an endangered critter. They ask P&F's help because their attempts at making money, like running a lemonade stand, ended in disaster. Unlike other instances of sudden ability lack on the show, it is not presented as ironic or even pointed out that these girls have been a race-pit crew, mission control on a space flight, and rebuilt a time machine despite faulty instructions. Yet they cannot run a lemonade stand. However, given that this is brought up 35 seconds into the episode, sets up a different plot and involves one of the Fireside Girls inexplicably covered in bandages, it's possible that this just counts more as Rule of Funny.
The Idiot Plots don't detract from the show since they're a large part of what drives it along, but they're there nonetheless (and, as stated, are a huge part of what drives it along). The only reason nobody discovers Timmy Turner's fairies is because of the stupidity of everyone else. Even when they're disguised as ordinary objects, with obvious faces, and they speak while in this state, in front of large crowds. Timmy's parents (and even random people on the street at times) will, instead of questioning Timmy's various talking possessions, simply remark that "That [object that clearly should not be speaking but did] is right!"
Timmy's Mom: Those gleeful goldfish are right to cheer!
A surprisingly good use of this trope is the first episode featuring Norm the Genie. Timmy is explicitly warned by Wanda that the genies are notorious tricksters and that their wishes always bite the users in the butt. The audience knows full well that it won't end well, but Timmy rationalizes using Norm anyway with this:
Even before the obligatory Reset Button at the end of each episode, people rarely notice or care about the huge, unexplained changes in Timmy's behavior/appearance/life or the city of Dimmsdale as a whole, even if they're personally affected.
Even more obvious is how most of Timmy's bad wishes that fuel episode plots could be easily resolved with one counter-wish. (Usually hand waved with "Magic can't affect [antagonist]!" or one of Da Rules blocking the counter-wish.)
Most of Timmy's wishes border on Too Dumb to Live territory, but Wanda and Cosmo generally say "okay, your funeral" instead of explaining why his wish is insane; Wanda has repeatedly gone on vacations or personal business alone when she knows that leaving Timmy and Cosmo on their own can and does result in The End of the World as We Know It.
One of the worst specific examples is "The Grass is Greener". The entire circus plot would literally have not happened had Timmy not overheard his parents talking about him, or more correctly would have not happened had his parents decided to phrase their opinion in literally any way that wasn't basically "Timmy is a worthless little prick who should have been a girl and then I would be much much happier... [Timmy walks out of earshot, sad, to go make preparations to run away] ...is the exact opposite of how I really feel!"
Two episodes had Timmy babysitting Poof, despite the fact that Poof is immortal, so he doesn't need protection. Given that Poof is Goo Goo Godlike, Timmy probably needs protection from him.
The plot of the episode "Man's Worst Friend" happens almost entirely because of Timmy Taking a Level in Dumbass and not being able to tell Sparky from his anti-fairy counterpart, despite the latter being, you know, completely blue.
In the to-date final season, Season 10, the idiocy of the entire cast of characters (sans Chloe, and even she isn't above making dumb decisions herself) seems to have reached critical mass. There are few plots and problems aren't instigated by either one or more characters (and not just Timmy, either) making ridiculously poor decisions, characters doing bizarre and/or dangerous things with no rhyme or reason, or by Cosmo and Wanda repeatedly being careless with their wands solely so Timmy and/or Chloe won't be able to solve their problems with magic/wishes:
In "Girly Squirrely" Cosmo and Wanda end up getting eaten by a bear and, for no adequately explained reason, Wanda tells Cosmo that they should dip their wands in the "bubbling brook" (that is very obviously the bear's stomach acids) to see how deep it is, and their wands end up ruined. What makes this example all the more baffling is that it was Wanda (normally the brains of the pair) who made this suggestion to Cosmo.
In "Fairy Con", it's made abundantly clear throughout the episode that Cosmo is considered the single worst and most incompetent fairy godparent ever, yet apparently every single fairy left their wands with Cosmo as they went into the con, and of course Cosmo, the clueless moron that he is, leaves the wands in a position to get stolen by Crocker at the climax of the episode.
Though the Justice League episode "War World" is closely adapted from a popular DC Comics storyline from the early 80s, "War World" is easily the weakest episode of the first season of Justice League, in large part because of its flaming idiot plot. This World's Finest review says it best:
"Ebert defines an "idiot plot" as a plot that could be solved in 5 minutes if the characters did not act like idiots. We get this in the very first scene, when Superman, J'onn and Hawkgirl are trying to detonate an asteroid. Something goes wrong with the explosion and Supes and J'onn are left stranded in deep space. We never get a full explanation for what exactly went wrong and who was at fault, a sure sign that the writer, having made one of the heroes an idiot, is trying to avoid pinning the blame on anyone. But if this person had not screwed up, we wouldn't even have a story. Nor is this the only occasion when someone acts like an idiot: Why are GL and Hawkgirl gassed in part two? Because they're arguing like idiots. In the fights on War World, why doesn't Superman just fly away from Draaga? Because he's an idiot."
And then there's the Justice League Unlimited episode "Clash", which relies entirely on Superman acting like an idiotic Jerkass for the story to work. Heck, even Batman points out Supes is acting rashly and out of character and Superman ignores him.
The JL episode "A Better World" only works because when JLord!Martian Manhunter comes to trick the Justice League into coming to his world, everyone takes him at his word, and no one even thinks about staying behind to mind the home fires, provide backup, work on the problem from a different angle, nor sending just an advance crew to verify the story in question. How many shapeshifting, mind bending, illusion-producing villains have each and every member of the JL fought? You would think at this point they would know better than just running off after someone because they tell a good story.
The Batman Beyond episode "The Call" only works because apparently, the Justice League no longer gives physicals anymore, allowing people to walk around for years under mind control, or infested by parasites. How many parasitic, mind-raping, body-snatching villains have each and every member of the JL fought? You would think at this point they would know better.
The Batman: The Animated Series episode "I've Got Batman in My Basement" is a very embarrassing example. As Batman ends up unconscious and a bunch of kids hide him in their basement. While Penguin is sneaking around the house trying to get back a treasure that Batman confiscated from him and is in the house, cue Penguin and his mooks acting completely incompetent as they get totally thrashed by the kids reenacting Home Alone. This is especially sad as it's Penguin's debut episode. Even the show's creators don't like talking about it.
Superman: The Animated Series had an episode called "Blast from the Past, part 1" with Mala, a Kryptonian Phantom Zone prisoner, being released because her sentence was rather light. Superman wanted to see if she could help him protect Metropolis and at some point in the episode, Superman loses all sense of compassion towards a person who had clearly been isolated in an Infernal Prison for years and constantly held the threat of being sent back over her head. The Idiot part comes in when you watch the episode and notice that Mala is genuinely trying to be Superwoman and the only reason she descends into villainy is because of the OOC jerkassery of everyone else in the episode.
The Simpsons does this a fair bit, though it's often justified in that everyone in Springfield is fairly stupid.
"The Great Louse Detective" involves an attempt on Homer's life, so the police bring in Sideshow Bob as a consultant. This is stupid enough on it's own considering that Sideshow Bob has tried to murder Bart numerous times, but the only measure they put down to keep him from doing so is a shock device attached with nothing but some tape around his leg. The only way the episode can work is if Bob is too big of a baby to rip the shock device off his leg at any time, especially since the device causes Bob great pain whenever the Simpsons press the button and thus the pain of removal would be preferable.
Even stupider is that the committee had already approved that they passed, and were just about to sign the papers before Skinner insisted that Bart go up.
"22 Short Films About Springfield" is a pretty good example, even for the universally dim residents of the town. Whereas Homer is already pretty stupid in his own right, here he takes it Up to Eleven by trying to get a newspaper out of a machine while juggling groceries, Maggie and Santa's Little Helper, causing his daughter to be trapped inside and having no way to get her out due to throwing all his other quarters on the the train tracks. Even more sensible characters get in on the idiocy: whereas Marge tries to get gum out of Lisa's hair by putting a variety of ineffective foods in it (even at one point smearing mayonnaise on her and telling her to go sit out in the sun), Principal Skinner, who is a Mensa member, burns the meal that he was making for Superintendent Chalmers and instead of manning up and admitting to what happened, makes up an outlandish story involving calling grilled Krusty Burgers "steamed hams" and localized Aurora Borealis instead of just turning his oven off. Predictably, his home catches on fire.
Played for laughs in "Treehouse of Horror VII" when Kang and Kodos impersonate presidential candidates Clinton and Dole during the 1996 election. They do a terrible job of pretending to be Clinton and Dole, but nobody really notices, and they end up chalking their blatant Evil Gloating, unnatural speech patterns, and unusually close relationship to just the eccentricities of politicians. Even when Homer reveals that they're both aliens who plan to Take Over the World as soon as either of them are elected, Kang still wins the election because nobody's willing to vote for a third party candidate.
Bender even has a virus scanner which catches the spam, but looks at it anyway.
Then again, most characters hold a deliberate Idiot Ball.
Leela (checking e-mail): Spam, spam, junk. (GASP) The very last pygmy rhino is going extinct?! Unless it gets my credit card number?!
"Bender's Game" features an idiot plot set into motion and resolved by Professor Farnsworth in one of his "less than worthy of being a professor" moments. Because fuel prices are higher than they were before, he reasons that the world would be better off if he and his crew went on a difficult quest to destroy the source of that fuel and then replace it with something almost the same... but infinitely inferior, effectively crippling society as they know it. This plot is made even stupider when another character, Bender, becomes so insane that he cannot distinguish fantasy from reality. He eats a shitload of radioactive waste that transports all of the characters into his dream, wherein they still try to accomplish the professor/wizard's idiot plot.
Later episodes show they did end up using a more efficient fuel-whale oil.
"The Day The Earth Stood Stupid" is an intentional idiot plot, with floating alien brains draining the intelligence of every person on Earth. The only one who's immune to it is Fry, due to lacking a delta brainwave...which means he's already The Ditz to begin with, and ends up only marginally smarter than everyone else.
The Weekenders: "Tish's Hair" hinges on Tish (the smart chick of the clique) reading a sign that's supposed to say "Your hair is the pits" as "Your hair is it" and not notice that it's been obscured by a tree, and hearing Carver's sister's comment "That's the worst I've ever seen" and thinking it's referring to Carver's shirt instead of her 'do.
In Teenage Mutant Ninja Turtles (1987), the episode "Zach and the Alien Invaders" is easily the biggest offender of this in the entire series, considering that the whole premise is about Zach convincing the Turtles that he's seen aliens, and robots, and other dangerous things that ended up being harmless, and getting in trouble for it. Because it's not like the Turtles have ever fought aliens or robots before, except you know like every episode where Krang and Shredder attack the Turtles with the Foot Soldier robots which happens on a regular basis! Later on Zach does see aliens that are trying to take over the world, and helps the Turtles stop them, but despite him being right about the attempted alien invasion, the episode ends with a horriblyBroken Aesop of "That's okay, Who listens to kids anyway?", which is why despite featuring the one and only appearances of Wingnut and Screwloose, this is easily still regarded as one of the absolute worst episodes in the entire series.
The episode "Leonardo is Missing" also falls under this, which is lampshaded by Splinter at the end, but unlike the first example, this episode is actually still fun to watch.
Splinter: Next time you leave, Leonardo, make sure to leave a note.
Splinter's backstory qualifies as this. The master's coming, and Splinter's rival pins his gi to the wall with a knife. Splinter tries to bow, and is verbally lashed by the master's aide for failing to do so, even though he's clearly trying and just as clearly is being physically stopped from doing so. He says nothing in his defense. He reaches back and pulls out the knife, and the aide thinks he's attacking the master even though he's just kneeling there holding the knife, not leaping forward and stabbing whilst yelling "SIC SEMPER TYRANNIS!" He's banished, and again he says nothing in his defense.
"Mikey Gets Shellacne" was the Flanderization for Mikey's stupidity. Not only did Mikey think putting more mutagen on him would make him a "super mutant" (despite Donnie having the foresight to write "Mikey do not eat me" on the jar of mutagen), he also turned Dogpound, who was an already sizable threat for the Turtles, into a stronger, faster, more powerful form. Coincidentally enough, Mikey gets his hands on the Smart Ball minutes later after this incident (which is a bit of an Ass Pull considering what this episode has shown).
In the episode "Your Baloo's in the Mail", the entire plot could have been resolved in the first scene if Rebecca had just trusted Baloo and told him that she had a winning lottery ticket that needed to be delivered first class to the lottery office the next morning. Or she could have done it herself. She just won the lottery, nothing short of major surgery couldn't be understandably postponed.
In the episode "Save the Tiger", Baloo saves Shere Khan's life in the first scene and Khan wants to repay his debt to Baloo by granting him any request he wants. Considering the fact that Khan said that his company is worth several billion dollars, Baloo could have simply asked for a couple million dollars in cash, bought the Sea Duck back from Rebecca, and lived a comfortable life like he always wanted to. Instead, Baloo constantly pesters Khan with tons of small requests and tries his patience which basically leaves Baloo with nothing in the end.
Invader Zim's whole series is based on this—the story could be resolved instantly if any human except for Dib noticed that Zim was obviously an alien. Their sheer stupidity is part of the humor, though. Even Zim and Dib themselves hold the Idiot Ball a lot, so a lot of specific episodes fall under this trope.
This was the subject of many Aqua Teen Hunger Force episodes. Master Shake was especially prone to these moments. An example is "Broodwich", where Shake could have saved himself a whole episode of trouble if he left the Broodwich alone.
X-Men: Evolution: "Joyride". To put it simply, villain Avalanche joins the X-Men to get into Kitty's pants. Scott doesn't trust him. Meanwhile, the New Recruits start taking the X-Vehicles out for joyrides. When it becomes obvious someone is taking the vehicles out for a joyride they start to suspect Avalanche. Two ways this could have been avoided: Lance could have told them it wasn't him and that he saw the New Recruits sneaking around, or Xavier could have checked their minds/Logan could have used his advanced senses to smell the cars and detect who had been using them. In the end Avalanche takes Kitty with him when he realizes they're taking the X-Jet, thanks to their presence, Jubilee accidentally fries the control panel, and they're nearly blown up by the US military. Avalanche then quits because life at the mansion is too hard. Also, with all of the security at the mansion, things were really flimsy enough that a group of kids who couldn't properly beat a training simulation could crack security and sneak off in the various cars and jets? Surely after it became apparent that someone was using the vehicles, the team would think to at least put a better lock on the garage.
The entire episode "The Super Speedy Cider Squeezy 6000". The presented "happy" ending of the episode was not anywhere near the best solution, but the entire plot could have been avoided in numerous ways, such as Flim and Flam offering a reasonable business offer, Granny not accepting their bet, Flim and Flam not allowing the Apple family to bring in additional ponies to help, the Apples not forking over control of the whole farm as a result of the bet (it wasn't part of the stakes), or the Apple Family hiring additional help from the get-go rather than attempting to do all the work themselves. In short, if anyone in the cast had even a modicum of business sense, there wouldn't have been any problems.
Even worse is their return episode, where they once again are scamming (despite being called out as frauds and run out of town before) and everyone (not counting the other mane 5) falls for it, except for Applejack. Worst of all Granny Smith herself falls for it the worst, as next to Applejack she should have been the first to call them out on their scams.
"Look Before You Sleep", also from the first season, has Applejack and Rarity fighting like children for the duration of the episode. Their bickering over an incomplete job trimming tree branches before a rainstorm spills over into Twilight Sparkle's first slumber party and nearly ruins her night. However, Twilight isn't any better in this episode. She becomes so infused with her slumber party guidebook that she thinks it can somehow solve the problem of a giant tree branch in her bedroom.
A lot of the conflict in the season 2 premiere "The Return of Harmony" could have been avoided if Princess Celestia had gone with the Mane Six rather than letting them stupidly wander in on their own. While it's true that she can't use the Elements of Harmony, she already has intimate knowledge of how Discord works since she's faced him before. Discord also could have literally ended the series with a single snap of his finger, thus saving himself a lot of trouble.
The season 2 finale "A Canterlot Wedding" has a lot of this. With the Mane Six and Shining Armor, it's justified since the former don't know Cadence and assume she's just being a Bridezilla, and the latter is brainwashed, but you'd think that at least Celestia would have picked up on the fact that something is seriously wrong about her niece. Even Twilight Sparkle, the Only Sane Mare of the episode, has a brush with the Idiot Ball when she barges into a room and loudly announces Cadance to be evil instead of trying to be subtle about it. On the villainous side, we have such gems as openly admitting you're an imposter after, only moments ago, fully convincing the only one suspicious of you, imprisoning Twilight Sparkle in almost the same room as the real Cadance, leaving the whole thing guarded by unarmed bridesmaids, and clashing with Princess Celestia (though she wins the fight, it's made amply clear she was not expecting to). Also, even though it's daytime and all, you'd still expect Princess Luna to wake up and help when the city is being invaded...
"Games Ponies Play". The entire plot revolves around the main cast not realizing that the pony they picked up from the train station wasn't the games inspector, something that could have been completely averted if any of them would have referred to her by name or in any way attempted to confirm who she was.
The season 4 finale. For one, Celestia's plan of action is to send the God of Chaos out to confront the Big Bad. Without sending backup. The premiere of the same season establishes that he's an untrustworthy guy, so Discord predictably Face-Heel Turns with the help of the Manipulative Bastard. So what's the next plan of action? Not telling the others about said betrayal. This allows Twilight's friends to easily get captured by Discord and later be used as a bargaining chip in the Big Bad's favor. They're only stopped because he was stupid enough to turn on Discord, who could have easily won for him, too early, and not killing Discord afterwards or the Mane 6 after draining Twilight.
In "Princess Spike", the conflict of the entire episode only exists due to the fact that the entire cast failed to handle the situation in the most logical fashion. A few examples include Twilight being sleep deprived because she had to plan an entire conference herself, Spike being given extremely vague instructions about what to do while she was asleep, leading to him creating a ton of trouble by trying to handle her duties for her, and Spike attempting to help Twilight sleep by stopping anyone near the tower from making any noise as opposed to closing the window, or maybe just getting her some earplugs. Better yet, she could've cooked up a spell to create a sound-free environment, like the one she comes up with on the fly two episodes later to chat with Moondancer in private.
In general, the bad guys almost never think to just knock out Twilight at the first possible opportunity. No matter how powerful the magic of friendship is, it can't do anything if Twilight (or Starlight in Chrysalis' case) isn't in any shape to invoke it. All they would have to do to dramatically raise the chance of success for any given evil plot is hire a goon or two to walk over and restrain someone who lacks combat experience.
On the flipside, the villains rely exclusively on their magic, so Anti-Magic should work perfectly fine on them.
"The Nasty Patty" episode of SpongeBob SquarePants where SpongeBob and Mr. Krabs thought they killed the health inspector, when all they did was knock him out. When the police arrive and they confess, the health inspector walks out of the freezer, dazed, leading SpongeBob, Krabs, and even the police to believe he is a zombie. Fortunately, he was not. It was all intentional, however, and the narrator even lampshades it at the very end.
Narrator: Yes, they are all idiots aren't they?
The conflict of the episode "Wormy" is sparked primarily by Sandy not bothering to mention anything about Wormy's metamorphosis.
The episode "Sandy, SpongeBob, and the Worm" relays on her stubbornness and not believing SpongeBob when he tells her that the Alaskian Bull Worm is WAY too big for her to handle and pissing it off is a very bad idea.
"Squid's Day Off" is equally set off by stupidity. Squidward could have done a few things besides going crazy with paranoia. He could have just shut the Krusty Krab down for the day and told SpongeBob to go home, he could have stopped trying to stay at home and just stayed in Mr. Krab's very comfortable office, or he could have just set the Krusty Krab's sign to "OPEN".
SpongeBob: It's almost like we could've taken the whole day off!
Ben 10: Destroy All Aliens arguably has this bad. The Omnitrix is clearly malfunctioning, but Ben does not tell Tetrax nor anyone else that could deal with it until the halfway point of the film. It doesn't help that, because of these errors in communication, Azmuth, who was visiting to fix the Omnitrix's malfunction, ends up being turned into an angry, incredibly dangerous To'kustar, causing his father to assume that Azmuth died, causing him to attack Ben, whose watch absorbed the To'kustar. This, again, can be traced back to Ben not telling anyone he can trust about the watch, to see if something's wrong with it, as well as admitting he was really grounded.
In The Avengers: Earth's Mightiest Heroes!, Wonder Man happened this way: Simon Williams goes to Tony Stark to demand to know why he's out to destroy his company, but Tony brushes him off and he storms out; this leads him to seek out MODOK and get revenge. They meet multiple times after Simon's been transformed into an ion-creature, but Tony never tells him that he only wanted to buy out Williams' company because it was failing financially, but he believed in Williams' scientific developments and wanted to work with him. He doesn't even tell the rest of the team until the end of the episode, after they've been calling him a hear.less bastard for ruining Williams' life the whole time!
One of the many criticisms made to Ultimate Spider-Man is to contain several examples of this: at certain points, the characters end up in a situation that would have never happened if not for 1) Spider-Man making a stupid decision or 2) Nova being an idiot.
The two parter "Blade and the Howling Commandos" could have been over in 2 minutes. Upshot - Dracula wants a MacGuffin that will allow him and his vampire armies to walk in daylight. The catch: it comes in two pieces that have to be united for the effect to happen. Blade and SHIELD have one piece. There is then a big argument about who Blade's team will be to go and find the second piece...as opposed to just breaking the one piece right there and calling it a day.
Distressingly common in King of the Hill, where pretty much any character (Bobby especially) will believe anything any random stranger tells them and then stubbornly hold onto those beliefs in the face of all contrary logic or facts. The pilot episode has throwaway characters who appear for all of five seconds assuming Hank is physically abusive towards his family, and as such Hank spends the rest of the episode fighting off a clearly-unqualified social worker who is constantly trying to move Bobby in with a foster family. It gets worse when they start reusing the basics of this plot, when characters (most commonly Hank) are accused of things that are clearly out-of-character for them (again, most commonly by throwaway characters who only stick around long enough to make those accusations) yet everybody refuses to believe them when they deny the accusations.
"Pigs Is Pigs", a Disney short from 1954, is a shining comedic second-order Idiot Plot (as is the Ellis Parker Butler story it was based on). Basically, the recipient of a package containing two guinea pigs gets into a dispute with a slavishly by-the-book railway agent over the shipping rate — the agent insists that they are actualpigs, and therefore the higher rate for livestock applies to them. The customer, unwilling to pay the extra four cents, leaves in a huff, and the agent sends a telegram to railway headquarters to determine the rate, which is shown to be quite possibly the most inefficient organization in the free world. The mountains of paperwork the telegram requires are essentially mindless busy work for the staff, the board of directors argue and bicker and fight for days, and have to employ a fact-finding staff and a zoologist to arrive at the correct answer. Meanwhile, the package remains at the station, where the agent allows the guinea pigs to breed unchecked (and their reproductive speed is exaggerated to Tribble-like proportions). When their numbers start to crowd him out of the station, he tries to slow them down by playing them Irish jigs. Eventually, the station explodes. When the agent finally gets word of the verdict, he runs to tell the customer only to find that he's moved without bothering to leave a forwarding address. The agent is left with no choice but to return the guinea pigs to the railway headquarters — and the original two now have a million descendants and counting. Thus, a conflict that could have been resolved in less than a day with a simple trip to the library ends.
Speaking of a simple trip to the library, Flannery (the agent) is actually shown reading out of a book entitled "Care and Feeding of Guinea Pigs". If he'd bothered to read past "A cabbage a day keeps the doctor away", he not only would have found out how to sex guinea pigs, and that the only way to keep them from breeding is to keep the males and females separated, he probably would have read that guinea pigs are, in fact, rodents.
In Gargoyles, it isn't uncommon to any character (no matter how intelligent) to hold the Idiot Ball, but "Eye of the Storm" takes the cake in Idiot Plot. In this episode, Goliath and co. arrive in Norway in the winter, and needless to say, Elisa can't withstand the low temperature as well as her gargoyle companions. Suddenly, Odin appears in disguise and offers a coat in exchange for the "Eye of Odin" (a powerful magical artifact and Odin's actual eye). Goliath, knowing the corrupting power of the eye and finding the idea of anyone trying to bargain with the life of an innocent immoral, refuses the offer. Pissed off, Odin leaves and tried to challenge Goliath in the form of a polar bear. When it failed, Odin proceeds to kidnap Elisa and vows not to release her until he gets his eye back. Goliath, believing that Odin doesn't deserves such power, but knowing that he doesn't stand a chance against a deity, is forced to use the eye himself, turning into an avatar of Odin. While he gains enough power to face Odin and rescue Elisa, he also becomes mentally unstable and tries to protect his friends by abusing his powers and trapping them in a cave. Only when Goliath almost killed his daughter did he realize that he was going too far and relinquish the Eye. As noted by several viewers (and Greg Weisman himself), the whole conflict could have been avoided if Odin had been honest from the beginning, rather than acting as a divine dick.
According to Greg Weisman the reason for Odin's Jerkassery isn't so much celestial douchery as it is a combination of Values Dissonance and Poor Communication Kills. By the ancient customs of Norway, Odin's offer of a trade was quite customary (similar to a modern reward for returning missing goods. The eye is after all rightfully Odin's), but Odin had not been in contact with mortals for centuries. He assumed wrongly that such customs were still used, leading to the conflict. To his credit, Odin actually admitted to having done wrong and apologized for his actions.
Elisa Maza was forced to carry the Idiot Ball in Deadly Force where we see that, despite being an experienced police officer, she is still dumb enough to just leave her gun lying around loaded in her apartment for anyone to find, which leads to Broadway, who shares the Idiot Ball with her by way of his complete and total ignorance of just how dangerous guns are, picking the gun up, playing with it like a child after sneaking into a movie theater to watch a western, and then accidentally shooting Elisa when he pulls the trigger, almost killing her. This continues to bite Elisa in the ass for the rest of the series when her idiot police chief forces an unwanted and mostly useless partner on her, Matt Bluestone, who spends most of the show just annoying the Hell out of Elisa and getting in her way, because the chief is apparently dumb enough to believe that any cop who gets shot needs a partner.
Though the Chief's idiot ball is actually justifiable. The ballistics of the bullet would've matched the ballistics on record for Eliza's assigned firearm, something they would have checked because she's a cop who'd been shot. So far as the Chief knows, Eliza has either allowed her gun to be taken and failed to report it (thus qualifying as incompetent) or attempted self-harm with her assigned weapon (and is thus of questionable mental state). Her ending up with a partner is insurance against both of those possibilities occurring again.
In "Call Girl" Lois gets a job as a call girl on a phone sex line. Not only does Lois not recognize the very distinct voices of men she knows, nor do they recognize hers, but Lois actually does what the callers tell her to do instead of just saying she did.
Furthermore, Peter falls in love with Lois over the phone (not knowing it's her) and she gets mad at him for "cheating on her". Completely failing to realize that if she doesn't change her voice or personality over the phone, then her idiot husband will fall in love with her all over again.
Almost every episode of the show (especially those revolved around Peter) revolves around this trope, usually completely intentionally.
The love triangle of World Tour between Duncan, Gwen, and Courtney. Courtney generates nothing but blind hatred for Gwen, who never tries to apologize to her throughout all this despite clearly feeling guilty for kissing her ex-boyfriend, and takes most of the abuse sitting down rather than defending herself. The fact that Duncan gets off scot-free for cheating on Courtney does not help.
One of the several reasons All-Stars had a negative reception was the fact that the treatment of the main antagonist revolved around this trope. Mal, an inherently evil alternate personality of Mike, takes over the latter's body so that he can wreak havoc For the Evulz and claim the million for himself. Unlike his predecessors, but much like his immediate successor Scarlett, Mal has no redeeming or comedic traits, and manages to make the sadistic host Chris look like a saint. However, he rarely formulates, let alone executes, a truly effective plan against all the other campers. Even though Duncan actually tells Zoey that he met Mal at juvie and therefore knows how dangerous he is, the majority of the cast, including Zoey herself, remains oblivious to the Malevolent One's presence. It is not until the end of the second to last episode does she finally learn the truth, and that realization occurred after many repeated warnings. The smarter campers never seem to catch on until it is too late, so Zoey is left to take him down in the finale regardless.
To make matters worse, demonic Alejandro and scary Chef both noticed Mike's unusual behavior and commented on it, yet nobody took action. One would have to think something was wrong when everyone watched Mal brutally beat Izzy to a pulp in the ring, but the idiocy rages on.
Take into consideration that most, if not all, of the plots probably wouldn't happen in the first place if Kevin, Nazz, Rolf, Jimmy, Sarah and Jonny (and Plank) simply ignored the Eds and their scamming (which they sometimes do).
Several early episodes of The Dreamstone seem reliant on this, either due to the Urpneys' Villain Ball Magnet role or the heroes' Story Breaker Powers. "The Dream Beam Invasion" is a glaring example, when the heroes find out Frizz and Nug have shrunk into someone's dream, the Dream Maker briefly forgets he can just get rid of the bubble so the Noops can shrink in and submit them to a gratuitous Kick Them While They Are Down sequence as a Plan A for getting rid of them, which only wastes enough time for the Urpneys to grow back and become large enough to scare away the Noops. Basically the heroes pulled the most evident Villain Ball in the show.
The common criticism towards Young Justice is that the majority of The Light's plans wouldn't have succeeded if the heroes of the show had acted just as intelligent or competent as The Light. Granted, this show's producer is the creator of DavidXanatos, so the villains are pretty smart. The team does wisen up by the end of both seasons and pull off their own gambits against the villains.
One episode of My Gym Partner's a Monkey involves Slips, the snake, shedding his skin. All the other students in CDMS are going through various changes involved with adolescence (such as Adam growing a chest hair). As a result, everyone believes Slips has a contagious disease causing them to go through these changes, and then they start a riot, causing Principal Pixiefrog to intervene and show them a video teaching them about growing up. The fact that none of the students were aware about growing up and blamed Slips for it places it into this category.
The entire show's premise of a human mistakenly sent to a public school for animals is an Idiot Plot that anyone could solve with a simple call to the board of education.
The entire second season of Frisky Dingo qualifies, because of the presidential election arc. Nobody seems to realize that Xander and Killface both fail to meet constitutional requirements: Xander is younger than 35, and Killface is not a natural-born US Citizen. They're eventually called out by a Pompous Political Pundit, but when it's too late to change the ballot.
The entire premise of Wolverine and the X-Men revolves around the idea that Xavier would trust Wolverine, a grumpy, burned out, roughneck loner with damaged memories and possible latent sanity issues, with the responsibilities of leading the X-Men. And that's before the X-Men all get kidnapped by ninjas.
Though Archie's Weird Mysteries has had its share of Idiot Plots, it's The Extra Terror-estrial that really takes the cake. The plot revolves around the gang helping an obvious E.T.Captain Ersatz called Gleebo who is being pursued by evil aliens, with the twist being that the "evil" aliens are actually cops and Gleebo is actually a criminal. However, despite the police knowing Gleebo's entire modus operandi being tricking others into protecting him, the police make no attempt whatsoever to identify themselves as cops despite wearing police-like uniforms with badges and speaking English fluently. The whole plot could have been avoided if the cops hadn't stupidly and repeatedly charged in with guns blazing, giving the gang every reason in the world to believe Gleebo's story.
Another episode, "Green Eyed-Monster", involves Archie jilting Betty and Veronica in favor of a new girl at school when he gets sick of their fighting over him. Archie, however, doesn't realize said new girl is actually a disguised fish monster who intends to take him prisoner in her underground cave. Betty and Veronica figure out the girl's true identity and try to tell Archie that he's in trouble, but he brushes them off repeatedly, thinking they're just jealous. Considering that this is far from the first unusual thing that has happened/appeared in Riverdale thus far, and the fish monster's human disguise has green hair, you'd think Archie would at the very least consider the possibility of Betty and Veronica being right, even if he was rather cross with them at the time.
Hulk and the Agents of S.M.A.S.H. runs on this. Nothing would happen in this show without some combination of random Idiot Balls being handed out to the cast, Forgot About His Powers, and Power Creep, Power Seep, among other things. People are continually out of character just to make random things happen in the name of driving the plot. In one episode, Thor asks Skaar to be an Asgardian prison guard. But not just any guard, Loki's sole prison guard. Keep in mind that Loki is intelligent enough to trick Dr. Doom into being his errand boy, and Skaar is slow even among the slow Hulks. Of course, Loki tricks Skaar into doing something horrible, and an entire episode happens because Thor doesn't have the good sense to not have one of (if not the) smartest liars in the MCU guarded by someone with the intelligence of a 7 yr old. Another episode only happens because Red Hulk, AKA General Thunderbolt Ross, a highly decorated US Army General, has no understanding of geography, and trespasses in Latveria, home to Dr. Doom. Then there's the premise of them holding the Leader as prisoner in their base (as opposed to The Raft or somewhere similar) after they capture him, even though the Leader is one of the smartest characters in the MCU, and no one on this Hulk team (even She-Hulk, who is a stunt woman in this incarnation) is known for their brains. Of course, Leader pwns their base later on in the season, and no one there can stop him because they're all idiots.
Played for Laughs in the Uncle Grandpa episode "Escalator", which has a worldwide panic caused by Uncle Grandpa and Pizza Steve getting trapped on a broken escalator. Not an elevator. An escalator. Lampshaded by Mr. Gus at the end, when Uncle Grandpa tells him they've tried everything, and he asks if they've tried just walking down.
Adventures from the Book of Virtues in the pied piper episode. Anne has to paint a fence for her mom, but she got invited to a birthday party. So to keep her promise to her mom, she asks Zach to do it, but doesn't want to pay him $15 for a job that only took an hour. Apparently, she never thought to simply either ask her mom if it was alright that she does it another day, do it earlier, or ask her mom if it's alright if Zach does it.
Avatar: The Last Airbender: The series finale relies on a monumentally stupid case of Poor Communication Kills on behalf of the heroes to force Aang to fight Firelord Ozai at the height of his power. Sometime offscreen after "The Day Of Black Sun", Aang, Sokka, Katara and Toph decided that since Ba Sing Se had already been conquered by the Fire Nation, there wasn't anything Ozai could use Sozin's Comet of +300 Firebending for, so they may as well wait until after it passes to challenge him. For some reason, none of them think to tell this to Zuko. Meanwhile, Zuko has learned that Ozai plans to use the comet to incinerate the entire Earth Kingdom continent, but doesn't inform the others of this because he thinks they must be planning to stop Ozai before then anyway so it doesn't matter. Had either side brought this up to the other early on, they could have gone after Ozai before the comet arrived and saved themselves a lot of trouble, but instead they keep quiet until the comet is only two days away and it's too late to do anything about.
Clifford the Big Red Dog: The episode "Boo!", features everyone around town freaking out over the giant ghost that's running around town... except that the ghost's actually Clifford. While many folks around town had gotten together to watch scary ghost movies in the first place, possibly causing nerves to get shot, it still shouldn't have been that difficult to figure out what the giant quadrupedal Bedsheet Ghost wandering around town was, especially folks who are very familiar with Clifford like the Bleakmans or Victor and Pedro.
Also, in the episode "Clifford's Carnival", Jetta is tasked with getting the door for the farmer bringing the tractor and trailer for the hay ride at the eponymous carnival. Jetta, however, gets distracted and is not there when the farmer arrives. What makes this an Idiot Plot is the fact that the farmer makes no effort to get anyone's attention, find another way in, or even open the door himself. He just stands there waiting for a long time before giving up and going home. In a sense, it's also an Idiot Plot in the long term as the carnival officials evidently didn't make it easier for the tractor get on the grounds in the first place. Although everything works out in the end when a hay trailer is attached to Clifford instead, if all parties had put more foresight into their actions, it would have saved them a lot of trouble.
Rugrats: The adults never seem to learn how to keep their infants from running headlong into the jaws of death multiple times. They just seem to set their kids somewhere with little if any supervision. They topped themselves by giving toddlers access to what is essentially a go-kart in the first movie, which led to them getting lost in the woods for days. And while the adults buckling down, getting some toddler leashes and playpens that weren't easier to break out of than Arkham Asylum, or at least hiring someone who wasn't narcoleptic as a babysitter, would probably kill the show, it's still jarring to see how much the show relies on Stu & Didi being candidates for most negligent parents in any medium. Especially considering the stakes are played fairly realistically.
Wakfu special episodes, those with the Ogrest, are riddled with this, sadly: couldn't Otomai have started by trying to reason with Ogrest? Or getting the Dofus out? Since, you know, it was his backup plan, presumably all along? Couldn't they have researched the feasibility of Count's idea in the first place, instead of just going with it, no questions asked? Couldn't lady Echo simply have explained her concerns instead of playing Mad Scientist? And why is everybody acting like such a jerk? They were able to discuss things before... Rubilax and Armand are suddenly the most reasonable of characters? Adamai sums it up well.
The Being Ian episode "Is There an Ian in the House" is driven by the utter failure/refusal of every so-called medical professional involved to recognize that Ian's leg isn't broken in spite of overwhelming evidence to the contrary.
This applies to several plots in The Flintstones, though like some of the other examples on this page, they're Played for Laughs. That being said, the climax of "The Hot Piano" (an early episode where Fred tries to get Wilma a piano for their wedding anniversary) is made possible by the fact that the Bedrock police apparently don't know what one of their most wanted men ("88 Fingers Louie", a person who takes pianos and sells them on the black market) looks like. Additionally, when they think Fred is Louie, (after simply seeing Fred with a piano he bought from the real Louie and assuming the worst) they shrug off both his and Wilma's insistence that Fred is not Louie; continuing to try and jail him until word gets out that the real 88 Fingers Louie has been detained. It does lead to a heartwarming and Funny Moment where Fred (with help from both the police and Barney) presents Wilma with the piano, but all the same...
The Star vs. the Forces of Evil episode where Star gets a bike, "Star on Wheels". Why doesn't Marco tell Star that she could use her feet, and not just the brake, since she doesn't know how to use it? Or the very visible hand brakes, since the idea of peddling backwards to activate the brakes threw the alien Star for such a loop? Or for that matter, why wouldn't Star just jump off the bike, given that she's got superhuman durability and couldn't possibly be hurt by doing so? Also, Glossayck's refusal to help, because it's a non-magic situation only adds on to the idiocy.
Another episode has Star go on the lam after she accidentally destroys a cop car. She does not think to try repairing it with her magic—granted, knowing her it might not have worked, but still. In any event, she hides outside by the river, rather than, you know, hopping into another dimension like she does every other episode. Why not go home to Mewni, or, if she didn't want to face her parents, stay with Princess Pony Head or something?
Teen Titans: The Brotherhood of Evil. Instead of, say, killing the heroes they capture, they decide to put them into easily reversible stasis to fill their Teen Titan collection of heroes. So when those they didn't defeat show up (because they never verified if they were dead), they release the ones they had captured and beat the crap out of them. To make things worse, the leader of the Brotherhood is a brain in a jar chessmaster with superhuman intelligence, and one of his top lieutenants is an immortal general who participated in almost every major war in history and is supposed to be the best strategist in the world. They should know better.
The Jedi and clone troopers in the entirety of the Search for R2-D2 two-parter would have saved R2 and destroyed the listening post with no trouble if it weren't for their insistence on bringing the obviously defective R3-S6 unit along and making it do important tasks that it inevitably screws up over and over again because it's a mole.
"The Gungan General" would have lasted about two to three minutes if not for every single character constantly taking leave of their senses:
It starts with Hondo deciding to hold Anakin and Obi-Wan for ransom. He apparently did not realize that when combined with taking Dooku prisoner in any sane universe, this would put him on the bad side of both the Separatists and the Republic (not to mention getting on the bad side of three of the most powerful and dangerous people in the galaxy).
Following this display of insanity, Obi-Wan, Anakin, and Dooku repeatedly forget that all three of them are powerful Force users who could easily get the restraints off or mind-control someone to do it for them.
It ends with Anakin holding Hondo prisoner and easily able to take him back for trial, only for Obi-Wan to instruct him to let Hondo go because they have no quarrel with them, apparently forgetting that Hondo kidnapped them, was planning on ransoming them, and tortured them when they tried to escape.
The Holocron arc features multiple characters, both good and evil, making errors in judgement.
The second half of "Lightsaber Lost" is ten minutes of Le Parkour which could have been resolved with three seconds of telekinesis via Ahsoka using the Force in order to take her lightsaber from the person she was pursuing. This is made all the more apparent due to the multiple uses of the Force in the episode itself, just not when it would have caught the lightsaber thief.
The episode "Shadow Warrior" is this as well, particularly on Grievous' part due to the errors that he makes in this episode.
The final arc of season five, which deals with Barriss Offee framing Ahsoka for bombing a hanger in the Jedi Temple. The entire Downer Ending could have been averted if Ahsoka had done a single thing that didn't make her look more guilty or if the Jedi Council and Republic Senate had bothered to even halfway try conducting a reasonable investigation.
Superfriends basically ran on this, as a consequence of having an enormous cast of heroes and badly outnumbered and overpowered villains, but a particularly notorious one is the plot of "Invasion of the Fearians." For reasons too complicated to explain here, the Legion of Doom has to terraform Earth to make it like Venus. They do so by tricking the Superfriends into doing things that are incredibly obviously bad for the planet, and also count on the presence of a specific member. For instance, Sinestro throws yellow asteroids at the Earth, and instead of just sending Superman or really anyone else to smash them, they send Green Lantern, whose Weaksauce Weakness means that his only recourse is to move the Earth out of orbit so the asteroids don't hit it. Then he doesn't put it back. The resulting Inferred Holocaust was apparently required for the process, and when the Superfriends figure it out, Green Lantern proceeds to easily move the Earth back, foiling the Legion's plan. Basically, it's the Legion relying on Superfriends doing the stupidest possible thing they could do in that situation, and the Superfriends doing exactly that and not trying to fix it until the last minute.