The titular character of The Amazing World of Gumball, despite the many times his schemes have gotten him and Darwin in trouble, never seems to learn from his past mistakes and continues to implement the same schemes that got him and Darwin in trouble before. Darwin does try to talk some sense into him, but Gumball mostly ignores his warnings.
Contrary to what he says in the page quote, in many areas, Stan of American Dad! doesn't forget certain Aesops (accepting his gay neighbors or his ethnic Iranian ones), but like the Peter Griffin example below, they have lampshaded his inability to do so in other areas.
Stan: There's something you should know about me by now, Roger. I don't learn lessons.
The episode with the page quote, concerning Stan lying that he came up with Roger's idea, ends with him taking credit for Roger's idea. Even shortly after lampshading his inability to retain lessons, he still forgets the current lesson.
Another interesting example and partial Lampshade Hanging comes with Roger. One episode ended with him revealing that he didn't really feel like a part of the Smith family, which is why he got insulted when they threw a comedy roast for his birthday (at his request). The others actually get indignant because not only has this issue been dealt with before, but in that episode and others they had repeatedly gone out of their way to please his ever-insane needs and desires. As Hayley pointed out, if he didn't think they cared about him by that point, it was his problem, not theirs. Roger seems to get it then, though who knows if it will stick this time.
Deconstructed in Archer. Sterling Archer never learns his lesson about being a better person, which makes him highly and reasonably disliked among his peers. However, a major recurring issue for Archer in this trope is that he is repeatedly made aware of his faults, and oftentimes doesn't simply blow them off or ignore them, but his efforts to truly change are often stymied as much by his dysfunctional coworkers and family as they are by himself; essentially, any progress he tries to make tends to get shot down because he continues to interact with people who directly feed his issues in the first place. Archer himself aptly sums it up in the Season 11 finale:
Sometimes happens on Arthur, but usually it's lampshaded with one character pointing out to the offender early on that they've learned this lesson before, while the offender tries to justify how the situations are different.
Avengers Assemble is incredibly bad about this, in particular about any stories surrounding the Hulk. Whether it's respecting his actual level of control over his anger, realizing that Banner and Hulk are two parts of the whole, or even just understanding that he is more than just "Hulk SMASH!", it never sticks and the lesson has to be learned again in another manner.
Though Hulk is the most notable of this, the other characters aren't any better. Iron Man letting go of his ego, Cap realizing that he's not part of a military team, Falcon realizing he isn't just an add-on, Hawkeye working with the team, Black Widow realizing she is part of a team to begin with, Thor with his relationship with Loki. Each lesson is learned and relearned over the series because none of them actually stick!
Ben 10: The sheer number of times Ben has learned lessons about being nicer to Gwen, that being a hero is about putting others before yourself, using the Omnitrix smarter not harder, and respecting other people, only to promptly discard them by the next episode is truly staggering. It's even lampshaded on occasion, with one of the movies (Ben 10: Destroy All Aliens) having Gwen quip that Ben is probably just going to forget the lesson he just spent the entire runtime re-learning again.
The 2nd Lucky Girl episode has Gwen also guilty of this, as the episode opens with her telling Ben, "You should be grateful for what you've got; I only got to be Lucky Girl for a few hours." And later, while they're talking about a new charm she found, we get a flashback to Gwen destroying the other charms of her own volition, while ignoring why she did this: to Be Herself, and also keep them out of Hex's evil hands. It's an actually positive use of the trope because the original moral was nonsensically saying that having powers was stopping Gwen from 'being herself' in the face of Ben who uses the Omnitrix all the time with no issue. In this case, the aesop is forgotten because well... it's worth forgetting.
Ben 10: Alien Force has Kevin Levin. He's constantly looking for a deal, and it's constantly biting him in the rear, usually because he trusts his old partner Argit despite the many times the latter has screwed him over.
Ben 10: Omniverse has Ben forgetting that he needs the help of his friends and family to be the hero he is, not to mention avoiding letting his fame go to his head. His new partner Rook calls him out on this, though.
Big City Greens is known for delivering moral lessons every episode due to its family-oriented nature, but The Hero Cricket has a tendency to forget what was just learned. For instance, he learns it's wrong to scam in "Wishing Well", but the episodes "Flimflammed" and "Chipwrecked" have him scamming others otherwise, and he learns to think before he acts in "Cheap Snake" but acts like he never did such in "Hurt Bike".
In the Big Hero 6: The Series episode "De-Based", Fred clicks a link in an obvious Four Nineteen Scam e-mail, which downloads a virus to Basemax. A few episodes later, he gets captured by Noodle Burger Boy when he misses every red flag in an obvious fake e-mail saying he won a contest he never entered. This is lampshaded when he says he's learned a valuable lesson, and Go-Go snarks that it feels more like a repeat lesson.
Bob's Burgers: Jimmy Pesto always seems to bring out the worst in Bob, and it takes a while for Bob to learn that struggling to one-up him isn't always worth the effort.
The 2015 reboot of Bob the Builder sees Scoop suffer this as a result of his regression into a childish idiot.
Brandy from Brandy & Mr. Whiskers was probably the epitome of this trope. Several episodes were about her either learning to care about others for a change or just care about Mr. Whiskers.
BoJack Horseman: Handled brutally in the season 3 finale. Diane learns she has more potential than writing shallow celebrity tweets...and ends up with a job writing for a feminist clickbait website. Princess Carolyn realizes that her job is making her miserable and quits it to concentrate on her love life...before starting a new career in a basically identical job. Only BoJack recognizes that his starring role in his rebooted sitcom is just him repeating the mistakes he always makes...which is especially sad because he seemed a lot more sincere about it this time.
Season 5 puts a slight backpedal on BoJack's Character Development from the previous 2 seasons. After a stunt accident while filming a crime drama show, BoJack becomes dependent on prescription painkillers to cope with both physical and mental pain. He breaks his promise to Hollyhock over never taking them again, which leads to him confusing fantasy and reality, and ends up choking his co-star when she tries to dispose of the pills. During an argument with Diane, he stubbornly refuses to take responsibility for his mistakes, which contrasts his Heel Realization in the aforementioned season finale.
Every single episode focusing on Zipper has the team dismiss him due to his small size/strength, which makes him leave, only for everyone else to realize what an asset he actually was and fully accept him at the end.
The "team ostracizes a character, so they leave, only for everyone else to miss them and want them back" plot point actually happens multiple times to every member of the Rangers except for Chip. In fact, it's often Chip who's complaining that Dale's too stupid/Monterey Jack's too hot-headed/Gadget's too scatter-brained/etc. that makes whoever it is leave.
Muriel and Eustace in Courage the Cowardly Dog continue to be fooled by the Monsters of the Week (such as Katz and Le Quack) even after said villains had tried to harm them in the past. Not even their old age excuses them since Eustace acts incredibly immature for his age and Muriel doesn't seem to lack any wisdom or awareness whatsoever outside of her eyesight when not wearing her glasses...or does she?
Count how many times Muriel has bashed Eustace on the head for mistreating Courage.
And let's also count how many times Eustace was warned to not do anything stupid that would inflict some ominous curse on him and/or the rest of the family and stubbornly flouts them by doing it anyway. Lucky for him, the show makes great use of the reset button.
How many times did Darkwing Duck learn to put aside his pride and get serious/ask for help/play well with others/etc.? Probably about once an episode.
The Dawn of the Croods episode "It Crushes" has Eep develop a crush on newcomer caveboy Kevin note You might be asking, "what about Guy, her boyfriend?" Well this was an Alternate Continuity or Broad Strokes prequel series set before The Croods. However, The Reveal in the final episode that the whole series was just Eep relating it to Guy just raises further questions. and spending the whole episode overcoming it. Then she's back to mooning over Kevin in all his subsequent appearances, despite knowing he's a self-absorbed Casanova. Somewhat justified, as Eep is a teenager and they don't always think rationally.
Dinosaur Train: Adventure Island: Thurston Troodon is an arrogant enemy to Mr. Conductor, who always tries to show off his latest technology and be the best. As shown in the television series, he has to relearn his lesson every time, and sure enough, in the feature film Adventure Island, he says mean things about the Dinosaur Train and was too overconfident in his fancy robot dinosaurs that he didn't test them prior to opening the theme park, and they go rogue following an earthquake. Thurston lampshades that he never learns his lesson towards the end of the movie.
Dino Squad: Caruso’s obsession with being famous and endangering the others in the process is in at least three episodes close together, even though he should have gotten the message the first time.
Yet another Disney example - the Disney Junior short series Nina Needs to Go!, which is basically Potty Emergency: The Series, will always end with Nina saying "That will never happen again because now I know - don't wait to go!" But then, it happens again in another scenario.
Fenton Crackshell kept learning that it wasn't his mechanized battle suit that truly made him a hero, but his determination, brains, and spirit. He still put that sucker on at the earliest opportunity every episode, though. (Well, wouldn't you if you had one?)
Huey, Dewey, and Louie never quite got the message "playing pranks on your [parent equivalent] to get something out of them will only backfire in the worst way, and isn't very nice besides".
It was done a bit better with Uncle Scrooge, however. While he remained very cheap throughout the series, he was willing to at least put the safety of his family ahead of money (although not always their comfort). (He did still have a number of episodes in each of which he learned anew not to be so stingy, however.) Partially justified in that Scrooge's primary focus has been making money, finding treasures, and pinching pennies since at least his late teens; it's probably hardwired by now.
Eddy lives and breathes this trope. Most of the Eds' failure in their scams are mostly his fault, and no matter how many times Edd warns him of a significant flaw, Eddy always ignores him instantly. It's not just the scams either. Eddy continues to taunt the likes of Sarah and Kevin even after the times each of those two characters, especially the former, have given the Eds a good beating on many occasions. Heck Edd actually lampshades this in two episodes when it came to Sarah. After the kids are horribly injured thanks to another one of Eddy's scams, they attempt to run after the Eds, who attempt to escape to the amusement park to go to Eddy's brother for safety. When the kids finally confront the Eds, they witness the pain Eddy suffers at the hands of his brotherand are downright distraught. After Eddy's brother is defeated thanks to Ed, Eddy finally learns that all he had to do was be himself, and the Eds finally gain acceptance from the kids.
You would think that after the 50th time the kids were bilked out of their money by the Eds, they'd learn not to ever give them a cent and never listen to a word they say. However, since the central premise of most episodes is based around the attempts by the Eds to scam the other kids only to be caught or otherwise fail miserably, the Cul de sac kids have to fall for the Eds' scams over and over and keep giving them their allowances almost every episode for the series to be able to work.
In "Ella Borrows Trouble" on Ella the Elephant, Ella "borrows" a number of things from her friends without asking. She gets into trouble for it and learns an important lesson. Yet, in "Tea Party Trouble," she "borrows" her mother's favorite earrings for the tea party without asking, resulting in one being stolen by a seagull.
By the time of the show, Kuzco has completely forgotten the lesson he learned in the movie, that it's notall about him, and relearns the same lesson in the series at least Once an Episode. To be fair, it's shown in flashbacks during the film that Kuzco has been spoiled rotten since he was in diapers; eighteen years of self-absorption and Jerkassery don't just go away overnight. That being said, while he is still incredibly self-absorbed and narcissistic in The Emperor's New School, he is also more solidly a Jerk with a Heart of Gold rather than a completely unlikable Hate Sink like he was in the early movie, and his selfish antics tend to be more dorky than truly mean.
The Fairly OddParents!: Timmy's had to learn not to act like a Jerkass ("A Wish Too Far!", "Power Pals", "Fairy Idol", "The Jerkinators"), his parents' rules are for the best ("Ruled Out", "Channel Chasers") and there are worse alternatives to Vicky ("Totally Spaced Out", "Vicky Gets Fired") several times. If you count episodes with a Fantastic Aesop, add "time travel is bad" ("Father Time", "Twistory") and "make sure magic gadgets only work for you" ("Deja Vu", "Presto Change-O"). Furthermore, most of the episodes' plots wouldn't even be possible if he actually bothered to remember the dozens, if not hundreds, of times he's learned to be careful what he wishes for or to listen to Wanda's warnings of the potential consequences.
In one movie, Timmy states that he secretly wished for the entire earth to not age. It took 50 years for them to find out what had happened. Apparently after those 50 years, he had gained absolutely nothing of value; no knowledge, no experience. All that time he didn't even bother to wish to find out if and how he would be caught so as to avoid it. He still doesn't bother to add two bits of sense to any wish.
Family Guy once lampshaded its own tendency to end with Peter describing whatever lesson he had learned by ending an episode with this exchange:
Lois: Well, Peter, I guess you learned a pretty valuable lesson. Peter: Nope!
There are at least THREE times that Peter Griffin has learned to love and appreciate his daughter and promptly forgotten it by the next episode. Twice it happened before the episode was even over.
An early episode had Brian coming to terms with his unrequited attraction to Lois, which was handled with a heart-to-heart conversation that was actually quite touching (especially considering this is Family Guy we're talking about). However, several seasons later Brian is outright obsessed with Lois, including trying to forcibly kiss her and convince her to leave Peter in one episode.
Foster's Home for Imaginary Friends: Bloo swings around between extreme Jerkass and Jerk with a Heart of Gold and virtually every time he finally realizes how life is much more fun if you're not consumed by childish egoism, he is reset back by the beginning of the next episode, or, worse, flanderized into an even greater jerk then before.
Parodied in Futurama'sShow Within a Show, The Scary Door. A Lazy Bum scientist builds a robot to do all the important things in his life for him, while he relaxes. Years later, he sees that the robot is the one who is given an award for a lifetime of scientific achievement. The next second, his son walks into the room and hugs the robot instead of him. Feeling a case of tragic irony incoming, the scientist tells the robot to experience it for him. The robot falls to its knees in horror, while the scientist cracks open a beer bottle.
Garfield and Friends: Played with in the two-part U.S. Acres episode, "Egg Over Easy"; Wade, who is afraid of everything, gets the idea to shell himself up in a paper mache-egg so he'll be safe when Sheldon tells him that he decided to stay in his eggshell to avoid the world's disasters.note Specifically, wars, the economy, and the NBC fall schedule. Wade soon finds out that there are disadvantages to being an egg, such as not seeing where he is going due to his eggshell obscuring his vision, and not being able to celebrate his birthday since he has to be born to have a birthday, and he can't blow out the candles or eat cake since his eggshell obscures his mouth. Wade also ends up getting captured by the Weasel, and he can't yell for help because his eggshell muffles his voice and he can't sound the alarm because his arms are still inside his eggshell. When Wade decides he doesn't want to be an egg anymore, he comes out of his shell and stands up to the Weasel. His friends save him, then decide to celebrate his birthday, feeling it only fair since he was finally born. At the end of the second part, Wade decides to shell himself up in another eggshell, figuring he should be safe now that the Weasel's gone. Bo is disappointed that Wade didn't learn his lesson and Orson feels that Wade's decision rendered the episode's moral pointless. Wade then gets chased by the Easter Bunny, who wants to paint him, learning that just because the Weasel's gone doesn't mean he's safe.
In the third episode, "Axed By Addition", Pete realizes that he has been a terrible father to his son, PJ, while he thinks PJ is sick and dying and spends the majority of the episode trying to apologize and ask for forgiveness for his mistreatment... then the doctors call him back, tell him PJ wasn't really sick, and he's right back to his abusive self for the rest of the series.
Mabel Pines had to learn several times over the course of one summer that she should not always put her wants above the needs of others, and that she should think more selflessly. Even though "Sock Opera" seemed to be written specifically to address this, towards the end of the series she was still willing to make a deal to place the entire town under a temporary bubble where time did not move forward after having a bad day where she learned the horrors of growing up and was met with the possibility of her brother not being there with her.
Invoked and parodied in Society of Blind Eye, where Blind Ivan feels a little bad when the negative repercussions of his amnesia ray are pointed out... only to zap himself with the ray to forget all about it.
He-Man and the Masters of the Universe Characters will often forget lessons learned in previous episodes. The most prominent example of this is Orko. On several occasions, he runs away because he feels his friends don't want him around, whether because they yell at him for screwing up or just ignoring him at times. At the end of every episode, there is a PSA about it, but since nobody in the show actually watches it, they all forget about it. Once, the Sorceress of Grayskull shows Orko how sad everyone will be in a year if he leaves. This doesn't prevent her having to save him in a later episode, unfortunately. Of course, Orko is not the only one with Aesop Amnesia. The other characters should probably realize that if one of their friends has the habit of running off at the slightest upset, they should probably walk on eggshells around said friend.
The Chained Heat episode "Bonding" showed Kim and Bonnie getting handcuffed together and learning more about one another in the process. Kim learns about Bonnie's family life, specifically her two sisters who belittle her at every opportunity. By the end of the episode, the two are getting along somewhat better, though by Bonnie's next appearance, she's just as shallow and mean as ever. This pattern pretty much repeats every time they're forced into a situation where they have to work together, and yet, never learn to get along.
Many, many times Ron learned the lesson about being yourself, and then promptly forgot about it. Actually lampshaded one time by Kim in "Ron Millionaire" where she mentions that he has a tendency towards this. It doesn't help.
One of the movies lampshades this even further, where Ron attempts to caution his younger self not to learn his lesson from one of these events in particular.
"OK, look, listen to me. In the future, you will change your hair and become a babe magnet. Keep that look!"
Well, the problem is at the end of the episode once he learned the lesson about his behavior he didn't need to alter his appearance back to the old style just because the new one had bad associations.
Another instance of lampshading could be argued to be the episode Team Impossible where Dash points out that Ron is supposed to be a master of mystical monkey kung-fu and Ron replaying that “it comes and goes”. Considering it “com[ing]” is almost always correlated with his self acceptance and self actualization, this is another example of his inability to hold onto those lessons.
Kim learns that her brothers can be helpful and not just nuisances at least twice, and to disregard peer pressure from Bonnie a good few times.
Kung Fu Panda: Legends of Awesomeness has a particular issue with Po never learning humility, passiveness, forethought, basically any aesop that could lead to things being better for him.
In The Legend of Korra, this is pretty clear from season 1 to season 2, as the headstrong Avatar Korra once again disregards the advice of her patient mentor to work for fast results with a Manipulative Bastardwho turns out to be totally amoral. As with her enemies, an elderly Toph even lampshades that an important lesson Korra often lets slip by is that nearly each of them had good ideas, but let them go too far. Toph even goes further to point out that Korra not learning her lesson is why she can't deal with newer enemies.
Just in general early on, Korra would often forget that she needs the help of her friends and family to be the hero she is, not to mention avoiding letting her status as the avatar go to her head. In Book 4, she cut herself off from the people she cared about, and Toph even points this out.
Actually averted with Tenzin. While the guy remains stiff and humorless throughout the series, he learns very, very quickly that Korra won't respond to rigid and studious teaching and that to be her mentor he has to bend a little. This lesson sticks with him throughout the series, and Korra consistently turns to him for advice when needed. He did attempt to be overly strict in Season 3 when teaching the new Airbenders, but that was because of bad advice.
The Loud House's main protagonist, Lincoln Loud, seems to suffer frequently from this as he ends up relearning the same lesson again and again. For example, after "No Such Luck", you'd have thought he'd stop telling lies for his own selfish needs, but "What Wood Lincoln Do?" came along and it shows him taking credit for other people's work, which is also cheating. What's the bet he'll forget that lesson again?
On Madeline, Pepito's cousins return in "Madeline and the Mummy" and seem to have completely forgotten why they stopped being brats in the last episode.
On The Magic School Bus, Janet seems to have relearned to not be such a snotty brat in just about every episode she appeared in.
Maryoku Yummy, being a series for preschoolers, tends to fall into this a lot. Every other episode, Hadagi has to learn not to be a big jerk, Ooka has to learn to be more responsible, and Shika has to learn that Maryoku is just right and stop fighting it already.
In Miss BG every episode usually deals with BG lying/telling tall tales, which in turn causes a massive problem amongst her friends and family, but she never learns her lesson for good.
Miraculous Ladybug has this in spades. If the characters learn a lesson in an episode (e.g. Marinette Dupain-Cheng learning she shouldn't let her crush on Adrien run her life, Adrien Agreste learning to stand up for himself, Chloé Bourgeois learning to be less of an Alpha Bitch, etc.), nine times out of ten they'll forget that lesson by the next episode and have to learn it all over again.
Molly of Denali: An educational example in "Bubbling Up." As it turns out, permafrost was making the stinky bubbles in Lake Qyah. Trini somehow doesn't know what permafrost is, even though she already learned about it back in "Not So Permafrost."
Candace of Phineas and Ferb has learned to have fun with life in every episode that's ever focused on her. A possible justification is given in one episode where we see inside her brain; at one point, her Id (which represents her desire to bust her brothers) wipes out sections of her memory; this could be taken to mean that her desire to bust her brothers is so strong that she voluntarily forgets any lessons she learns which would get in the way of it. Plus, even without that her basic sanity is... dubious, at best.
The Owl House: Zig Zagging. Luz Noceda wants to be able to do magic more than anything, but her impatience leads to her always trying to skip past the boring learning part, which always ends in disaster. Yet, time and again, she goes back to looking for a shortcut instead of realizing that, for her to really do magic, she needs to learn the old-fashioned way by just studying and slowly growing her talents. On the other hand, she and Eda are making up her education regiment as they go along since she lacks a magic bile sac and Eda can't see the glyphs that Luz can. It's natural that Luz keeps trying to see if the next adventure has the answer.
The Powerpuff Girls have it pretty bad, but then, they are portrayed as being in kindergarten, so it might be understandable that they don't always remember the lessons they've learned very well.
Meanwhile, the villains continue to try to take over the world, rob other citizens, and commit other otherwise illicit deeds even after the girls give them a good beatdown. Mojo Jojo, in particular, especially falls towards this whenever he conceives a diabolical plan to take over Townsville and destroy the Powerpuff Girls, not learning his lesson for the many times he keeps overlooking a flaw in his schemes and not taking the painstaking effort to put them into full detail before he implements them.
Parodied in Rick and Morty. Mr. Needful had given Mr. Goldenfold aftershave that made him irresistible to women, but also impotent. Upon confronting Needfull about it, Needful declares that everything has a price and laughs evilly. Goldenfold breaks down, declaring that he deserves what he got for his greed and hubris. Rick shows up, cures Goldenfold's impotency, keeping the aftershave's positive effects, and Goldenfold immediately runs off with several beautiful women, yelling "I haven't learned a thing!"
Rocket Power: Otto Rocket. Oh boy! Where do we even get started on this arrogant kid? Well to put it short, of all the times he disobeyed any authority figure's demands and warnings not to do anything that would get him into major trouble (such as snowboarding off the big jump and sneaking into the back bowl that is off-limits), it's a wonder why Raymundo didn't revoke his skating privileges for a while.
Rocko's Modern Life: Right after having a near-death experience involving going to Heck for the sin of gluttony, Heffer instantly asks Rocko if they could stop at another restaurant on the way to the movies. Rocko yells "Have you learned NOTHING?!" and takes off his face, revealing himself to be Peaches.
The babies of Rugrats get tricked by Angelica pretty much every episode and yet keep believing almost everything she says. To be fair, they are babies.
Instead of solving her problems on her own, Sabrina goes to the Spooky Jar (A Cookie Jar that contains a genie-like entity who is actually a Jerkass Genie) to solve her problems, only to create much much worse problems in their places. Despite this, she still uses it in several other episodes.
Any time Gem learns to accept and get along with Sabrina will have been forgotten by the start of the next episode. Sometimes this can be justified by use of magic, forcing Gem to forget about the experience. In other episodes, Gem really has no excuse. At the end of "I Got Glue Babe", Gem is already back to being a Rich Bitch about twenty seconds after she and Sabrina manage to unstick themselves after being stuck together for most of the episode.
In a first-season episode of The Spectacular Spider-Man, the Chameleon begins a crime spree dressed as the eponymous hero. J. Jonah Jameson, being who he is, immediately prints a story in the Bugle declaring him a criminal; of course, by the end of the episode, the Chameleon is revealed to be the criminal and Jameson is forced to print a retraction, something he had apparently never had to do before. In the second season, Venom also begins committing crimes and general violence while impersonating Spidey. Jameson soon ends up at the police station, demanding to know why Captain Stacy hasn't begun efforts to arrest Spider-Man yet. While calmly explaining his evidence saying that Spidey was not responsible doesn't work, Stacy simply calls him out on this:
Captain Stacy: This isn't the first time the Bugle got it wrong when a copycat dressed up as the webslinger. Now do you really want to embarrass yourself and your paper...again?
The above version of Jameson nails the comics Jameson perfectly in that regard. In the comics, he'll accuse Spider-Man of either being in cahoots with the current villain or BEING the current villain, as well as fall for the copycat Spidey routine time and time again, and he never learns and keeps doing it, even brushing off those who try to remind him what happened last time he did that.
While lessons the boys learn tend to stick ("Big Gay Al's Big Gay Boat Ride," for example), the same does not apply to the adults. No matter how many times Randy or Sheila learn lessons about actually listening to their children and respecting their wishes ("Bloody Mary" and The Movie, for example), they're back to publicly humiliating Stan and Kyle by the next episode.
This would also apply to Cartman, except he is a sociopath and one of the symptoms of a sociopath is a general inability to learn lessons at all.
Stan also has his moment at the end of "Two Guys Naked in a Hot Tub". After Pip, Butters, and another nerd help him save the lives of everyone at a party, Stan announces that he's learned not to judge nerds just for being different. Then Kyle walks by, and Stan starts complaining about what nerds they are.
The boys also frequently "learn lessons" about blaming their behavior on external influences, such as in The Movie. The trope is lampshaded to Hell and back in "Butt Out" (where they blame the tobacco company for making them smoke) by Kyle, who suggests that they come clean instead of letting things spiral out of control. Stan makes two such "I learned something today" speeches in a single episode. In "Chimpokomon", the kids are brainwashed by the Japanese into attacking the US. When the parents figure out how to snap the kids out of it, Kyle decides to go through with the attack. So Stan gives a "learned something" speech about the evils of blindly following the crowd. Kyle agrees and claims that, since all the kids refuse to attack, he still has to do it in order to prove his independence. Stan immediately does a speech saying the exact opposite of the first speech, completely confusing Kyle.
They also never seem to realize that whenever they (Cartman in particular) get involved with a Get-Rich-Quick Scheme (for whatever reason), things end badly such as the "Pandemic" Multi-Part Episode, where they are wrongfully sent to Peru after they start a pan-flute band. Not to mention Craig, who was roped into the scheme gone wrong, spends the entire two-parter lampshading this about the four main boys.
Any episode that focuses on Mr. Krabs' incredible greed. One could guess that love (of money in this case) conquers all.
Also, Squidward has learned to be less grouchy and to appreciate SpongeBob and Patrick‘s kindness, only to forget it by the end of the episode (or next episode at the latest), far too many times to count. Then again, SpongeBob and Patrick never seemed to learn that brazenly intruding into someone's life and ignoring their requests to be left alone is NOT an appropriate way to express kindness, so that one may be justified.
Star Trek: Lower Decks: In "No Small Parts", in-universe, the people of Beta III are letting Landru boss them around again, in spite of Kirk's speech and a "Do Not Obey" sign that his crew left behind.
Beast Boy learned several times not to be such a goof-off. It never quite took, at least completely. Same for Cyborg learning to accept not being human anymore.
Oddly enough, the rest of the team seemed pretty good about avoiding Aesop Amnesia. When Raven and Starfire learned to respect one another's differences, it stuck with them through the rest of the series.
Even more oddly, the last time the series dealt with Cyborg's humanity this trope was actually inverted. Cyborg goes Machine Worship too hard and has a Superpower Meltdown, requiring him to learn the opposite lesson. Poor guy just can't win.
Robin still struggled with not being a Jerkass throughout the series. He was trained by Batman so it isn't surprising he would default to Jerkass. Robin finally ended up throwing away the Jerkass Ball (mostly) for good after the episode "Haunted".
Early on the turtles learn the dangers of becoming overconfident. From then on, they end up becoming cocky again multiple times. However, when this happens Splinter is usually quick to humble them again, or they suffer the consequences of it in battle. This helps to make it feel like a realistic character flaw instead of shoddy writing.
Several episodes have repeatedly focused on Raphael attempting to control his anger issues. Something goes wrong because he generally can't control his temper, he realizes how much of a problem it can be, and then another episode puts him back at square one.
In Thomas & Friends, after the 5th season, Thomas and Duncan become especially prone to this. In fact, Thomas's character up to the 5th season was built on Aesops from past experiences in the earlier seasons. Suddenly, when season 6 debuted, he was a perfect schoolboy type. With the debut of season 8, he seemingly forgot every lesson he ever learned.note However, this is likely because this was the point where the show had been sold to a new company. It's even worse when he forgets the Aesop of patience by the very episode after he learned it. James is quite bad for this too, but it may be justified considering his personality.
The reboot, Thomas & Friends: All Engines Go, plays this straight up until "Thomas and Percy's Eggscelent Adventure", when Thomas asks to deliver eggs and other fragile ingredients. Gordon is reluctant to entrust this delivery to Thomas, because of his previous failures that he has done, listing examples (alongside Percy) from previous episodes. He entrusts the task to Thomas anyway but asks Percy to go with him.
In the episode "Song of the Petalars," young Lilliputian Emrick (questing to restore his people to their homeland) impulsively confronts a bird so large he's outmatched and protagonist Lion-O must save him. Lion-O complains of his teenage stupidity. Later, Lion-O (questing to save his people and their homeland), in his teenaged stupidity, impulsively leads his ThunderCats to confront enemy forces so large he's outmatched and a Deus ex Machina must save them. When Lion-O attempts yet another Leeroy Jenkins in "Old Friends," his new mentor Panthro quickly loses his patience.
In "The Pit", Pumyra is distrustful of Lion-O until he nearly gives his life to save her. In "The Curse of Ratilla", Pumyra is distrustful of Lion-O until he nearly gives his life to save her. In "Birth of the Blades", Pumyra is — get this — distrustful of Lion-O until — get this — he nearly gives his life to save her. Of course, knowing what we know now, this may well be justified.
No matter how many times Harold from Total Drama Island manages to save the day at the last minute with some special skill that only he has, future episodes will always have the other characters, especially Duncan, proclaiming that he's useless and should not be listened to/trusted to do any sort of task.
Astonishingly, the episode where Harold is treated the worst in this regard comes immediately after the one where he single-handedly saves everyone from drowning!
On Timothy Goes to School, this is generally averted. When the kids learned a lesson on the show, it tended to stick. For example, in "Fritz in the Mess Fairy," Fritz realized that there was no mess fairy and he needed to clean up after himself. Him being messy was never shown as an issue again in the series, despite the story's Here We Go Again! ending with Fritz having made another mess with the cleaning supplies in the process of cleaning Timothy's seashells. In "Small Change," Nora learns to accept and even like change and she is never shown having an issue with it again. And if Lilly still sometimes forgets things, it can be forgiven, as it's difficult for her, and she does try hard and sometimes succeeds.
You can practically mark it off on a checklist for every episode. One or more of the girls experiences a personal issue that could be easily solved with a little extra thought. They go on a mission that somehow relates to whatever the personal issue is. They learn from said mission how to overcome the issue. Cue scene in the last thirty seconds of the episode showing they haven't actually grown or learned anything.
There are multiple episodes where Britney joins the team and Alex gets jealous and thinks she's trying to take her place.
A disproportionate number of episodes in Transformers: Animated feature the plot device of Bumblebee being a cocky showoff, going off on his own, and messing the whole thing up in order to learn the value of teamwork and actually telling your leader what's going on. At least once, this has happened two episodes in a row.
There were also a lot of episodes in the first season that revolved around Sari recklessly using her Allspark key and having to learn that Allspark energy is not a toy. Thankfully, she did get much better about this by the time season 2 rolled around.
This is a fine tradition in Transformers, dating back to the original show where Optimus Prime would actually sum up the Aesop of the story to all the Autobots at the end of the story, just in case it wasn't blatantly clear enough. Amusingly, this probably technically makes the Autobots' Aesop Amnesia disobeying orders.
Just like Animated Bumblebee, Miko from Transformers: Prime also has to learn (and forget) a lesson every other episode. Which is: rushing headfirst into trouble can, well, lead to trouble. In fact, this has been the basis of so many episodes in the first season, some fans tend to chant "Oh, it's one of those episodes again..." when they see her doing something reckless.
Xiaolin Showdown had a couple of Stock Aesops, all of which were repeatedly learned and forgotten. A sampling includes "Don't futz around with the Shen Gong Wu for frivolous reasons", "Don't screw over your teammates", "Stop being jerks to each other". And while not really an Aesop, it was still rather glaring how they never learned that yes, even Jack Spicer can come up with a winning plan every so often, so don't just automatically shrug off what he's doing because he's a loser.
Daniel Tiger's Neighborhood has a bit of an unusual case. While lessons generally seem to stick from episode to episode, they often seem to take a while to sink in within a particular episode. For example, in "You Are Special," O has to hear several times "I like you / I like you / I like you / Just the way you are" before he stops trying to do stuff to be like the other characters to be special.
On ToddWorld, the show's prevailing aesop can be summed up as "everyone is different and it's important to understand, respect, and celebrate those differences." Yet in many episodes, this will be forgotten. Stella is the usual offender, but it can hit just about any of the main characters.
Possibly intentional in Season 5 of The Adventures of Puss in Boots, which has several episodes in which Puss and the San Lorenzans learn not to ignore Butt-Monkey Eames, but never seem to remember this, because it's Eames, and he's just that forgettable.
Voltron: Legendary Defender deconstructs it with Keith. He learns the fact that he can't be a hothead and needs to put the team's best interest before his own and forgets it every time. This comes to a head when he commits the same mistake after learning it in the very same episode, which leads to his team facing a threat without him and almost dying, leading Shiro to get back into Voltron and him to leave Voltron for the Marmora.
