Adventure Time: "The Red Throne" was considered by many fans as one of, if not, the most reviled and hated episode of the series, due to Finn acting like an immature teenager trying to win Flame Princess back after their already controversial break-up in "Frost and Fire" and "Earth and Water" while trying (and ruining every attempt) to help her reclaim the throne, Cinnamon Bun becoming smart via an Ass Pull and the ending, with Cinnamon Bun saving the day and declaring his love to FP. Season 7's "Bun Bun" not only reunites the two again after not talking to each other for an entire season, but none of the events of "The Red Throne" are mentioned or referenced whatsoever in the episode and the rest of the series, meaning that most of the episode was retconned from the series (that and the Fire Lord being removed from the series due to Roddy Piper's death).
The episode "Best Burger" is one for the much-maligned "Family Fracas", giving us another competition between Bob and Jimmy Pesto, with Chuck Charles overseeing the event. While Bob still does not win, Jimmy crashes and burns hard, the contest between Bob and a famous chef is an incredibly close run, the winner was a deserving Nice Guy, and the restaurant picks up a significant amount of business on the back of it.
As a whole, the reaction to this episode made the writers learn that it's just not fun for the audience when the characters they root for lose for no reason and the Hate Sink wins. Subsequent episodes show Jimmy Pesto and Hugo either as laughably incompetent or losing for their efforts to do things in the most jerkish way possible.
"All That Gene" serves as one to "Gene It On" by being another episode about Linda and Gene's relationship. "Gene It On" had Linda desperately wanting to live vicariously through Gene's cheerleading and smothers him in attention to do just that until Gene finally snaps at her and she declares he's "not her favorite anymore." "All That Gene" shows Linda genuinely wants to help Gene get the part of Quiet Eli because she believes in him, but the lengths of bribing the director undermine her best interests and causes a rift between them before Linda makes amends. The problem with "Gene It On" being Linda doesn't really learn why she was wrong to treat Gene the way she did, while "All That Gene" has Linda making a well-intentioned mistake for the sake of supporting something Gene really wanted to do and then making a better effort to offer him true support.
BoJack Horseman: Despite its public and critical acclaim, many fans felt that Season 3 was unreasonably punitive of BoJack, and that he didn't deserve most of what happened to him, despite his previous actions. The Downer Ending to his plotline while everyone else's ended on a positive note didn't help. Season 4 appears to be made with this in mind; BoJack makes major strives in more positive Character Development, makes some amends with his mother, finally manages to not destroy a relationship with his half-sister Hollyhock, and several of his broken friendships are, if not mended, then at least patched up. BoJack even gets to drop the season's sole F-bomb. His own ending is an unambiguous Hope Spot, while the overall angst is about evenly divided by the Ensemble Cast, with Diane and Mr. Peanutbutter's marriage breakdown, Princess Carolyn's miscarriages and Todd's sexuality issues.
Daniel Tiger's Neighborhood had the episode "Daniel Can't Ride Trolley; Daniel Can't Get What He Wants". Both segments in the episode had a moral of "stomp your feet when you get angry and you will feel better". Unfortunately, this seemed very similar to a temper tantrum in the eyes of most parents. A recut version of this episode was made in 2019, with some scenes edited and the line "stomp three times" redubbed with "Take a deep breath".
In "The Time Traveler's Pig" and "The Deep End", Dipper has to sacrifice his potential happiness for Mabel, causing fans to complain that she never even considers doing the same. In "Sock Opera," Bill Cipher actually uses this argument, and Mabel's treatment of him in that episode, to trick Dipper into letting Bill steal his body. When Mabel confronts "Bipper" at the end of the episode, he almost talks her into sacrificing Dipper for her own happiness...only for her to remember how often he helped her and refuse, saving the day.
In Justice League, a three-part episode ("The Savage Time") revolves around the Justice League trying to Set Right What Once Went Wrong after Vandal Savage usurps control of the Nazis and uses them to conquer the world by way of time travel. They succeed, but the episode ends with Hitler about to be cryogenically defrosted and restored to power. This led to a massive fan-outcry, to the widespread Fridge Horror that this implied the Justice League had blithely restored the Holocaust in the process of returning to their own world. It got so bad the producers publicly stated that Vandal's manipulations meant that Hitler had neither the time nor the resources to enact the Holocaust, having been frozen before he could start and then put back in charge during the end of the Nazis' reign over Germany.
When Brainiac makes his return, he created a skullship. It's design is more closer to the comics and is meant to address complaints some people had with the other skullship that appeared in Static Shock.
During the first season, Superman had the tendency of being defeated by a number of villains frequently, sometimes in ways that wouldn't logically incapacitate him, which netted complaints. The writers caught on and the second and Unlimited seasons brought him more in line with how he was back in Superman: TAS, which resulted in him not being knocked down as easily.
In the first season, there was a Courtroom Episode where Kaeloo wins against Mr. Cat by emotionally manipulating him and then harshly punishes him despite him being nice to her for once. This episode was hated by nearly the entire fandom, who thought the episode was too unfair to Mr. Cat. Then, Season 3 had another Courtroom Episode, and this time around, Mr. Cat won by hoisting Kaeloo by her own petard, which the fans thought she deserved.
Episodes like "Let's Play Golf" and "Let's Play Danger Island Survivor" prove that Kaeloo is not a Karma Houdini after all, assuaging the wrath of fans who watched the episodes where Kaeloo does get away with some pretty shitty stuff.
Fans of the series who felt like Mr. Cat and Stumpy got too much screen time were pretty happy with Episode 149, where Mr. Cat does not appearnote For the first time in the series and Stumpy is relegated to a minor/supporting character while Kaeloo and the bunny twins get more focus.
Many fans of the show felt annoyed by Kaeloo's constant manipulation of Mr. Cat's emotions and her using his love for her against him. In Episode 108, we get to see her emotional blackmail backfire on her while Mr. Cat watches with a confident smirk.
In Episode 171, we find out that Mr. Cat's constant tiredness is his own fault for staying up late at night instead of sleeping, assuaging fans' fears that he was sleep deprived because of the other characters bothering him while he tried to sleep.
The extensive Love Triangle subplot between Korra, Mako, and Asami in Book 1 of The Legend of Korra was widely panned as bring rushed, getting in the way of the real story involving the Equalists, and ultimately feeling shallow and unsatisfying. Season 4 featured a Clip Show episode with the first segment exclusively dedicated to Mako's messy love life, with side characters pointing out all the mistakes that Mako made. Mako ends up agreeing with them and admitting his mistakes, in what was basically an apology to the fans. In general, Book 3 was this after Book 2 in correcting numerous mistakes from re-railing several characters that had been become jerks, idiots and/or weak, giving a proper reason for why Korra had been secluded instead of the White Lotus messing up Aang's wishes, more compelling and coolervillains to overall getting back to the franchise's Central Theme that meant the women were rivaling the men in competence again.
The Lion King (1994) spin-off The Lion Guard's very first episode addressed the long term criticism of The Lion King promoting "segregation" of the hyenas and the portrayal of them as evil. Jasiri is the first non-antagonistic hyena introduced in the series (the second if you count book canon) and she mentions that the roles hyenas play are just as much a part of the Circle of Life as the lions. It goes so far as to retcon-away the evil nature of hyenas; apparently they are mostly good as a species, it's just The Pride Lands have coincidentally seen more evil ones than good ones.
Some viewers of The Loud House found Clyde's crush on Lori too weird, especially how he'd get a nosebleed, act like a robot, and pass out. Later episodes had him obsessing over Lori a lot less, and when his crush on Lori was brought up, he'd usually do something mundane like imagine being married to her or get hearts in his eyes, rather than bleed, pass out, or act like a robot.
In Season 4 of Rick and Morty Beth and Jerry's "relationship" is barely even touched on, and when it is it's typically very briefly to set up a joke. This is in direct response to fans coming to dislike the two and how their marriage problems were focused too much on, particularly in Season 3 where they bordered on taking the spotlight from the titular Rick and Morty, and fans complaining that Beth and Jerry are much more interesting and entertaining characters when they're not constantly padding episodes with their relationship drama.
The Simpsons episode "Brother, Can You Spare Two Dimes?" was hastily developed and tacked onto the end of Season 3 after the negative response to the Downer Ending of Season 2's "Oh Brother, Where Art Thou?", and specifically overrides said Downer Ending, with Herb regaining his fortune and reconciling with Homer.
The episode "The Principal and the Pauper" was widely derided for its revelation that Seymour Skinner was actually a former petty thug named Armin Tamzarian who assumed the real Skinner's identity after the latter went missing in action in Vietnam, made even worse by the fact that the real Skinner ends the episode expelled from Springfield while the impostor carries on with his life. "Boy Meets Curl" made all that Canon Discontinuity, firmly establishing that the Principal Skinner we've been following is in fact the real Seymour Skinner.
One aspect of Gem fusion that made many viewers uncomfortable was the idea of romantic partners giving up their personal autonomy to live full-time as a combined being like Garnet. The Steven Universe: Future episode "Together Forever" addresses this by revealing that Ruby and Sapphire sometimes willingly split (as opposed to when they're arguing or on a mission that requires their separate selves) to pursue their own separate interests. Garnet explains to Steven that a healthy relationship isn't about people completing each other, but complementing, and that her two component Gems still live their own lives independent of each other.
In Teen Titans, Cyborg was always shown firing his sonic Arm Cannon from his right arm, until one day he used his left. Fans pointed out this apparent plot hole, and some time later, during a crucial fight, he simply converts both arms to cannons.
A complaint some had about the Loads and Loads of Characters that were introduced in Invasion, was that many of them were dumped in rather haphazardly, especially prominent with the second iteration of the Team. It introduced seven, later up to nine, new Team members but of them only Blue Beetle and Impulse got a lot of focus, giving the impression that the others were kind of just "there" in the midst of the large cast (it didn't help that Executive Meddling cut Invasion to 20 episodes from the planned 26). Now, while Outsiders also introduces many characters in the first few episodes, many of them are cameos until later, while the three big new additions to the main cast in the early episodes — Black Lightning, Geo-Force and Halo, are given proper development before focusing on new and other cast members. Same could be said for later recruits Forager and Cyborg, both of whom are very well-developed after their first appearance.
Terra being The Mole is made clear at the end of her debut episode, showing that the writers are aware that this plot point is already well-known as opposed to kicking around it.
The irony with the above is most, if not all, of the heroes are ALSO aware from the very beginning that Terra is The Mole compared to most versions where no matter how explicitly evil she is, they're completely unaware and blindsided. The changes allow the viewers to get a look into Terra's mindset and understand why she is willing to spy for Slade (and why she ultimately turns on him when she realizes the heroes truly care about her) and also allows the heroes to seem far more intelligent.
It was a very common complaint among fans that The Light in the first two seasons often bordered on, or were, Invincible Villains, with even the hardest fought victories ultimately resulting in them gaining some kind of benefit that negated whatever the loss they incurred. The second half of the season has Zatanna cleverly trap Klarion in Fate's Tower (though this is later somewhat undermined by him seemingly escaping off-screen, if his appearances in the Light's view screens in some of the last episodes of the season, including the season 3 finale, are to be believed) and in the next episode has the Outsiders outmaneuver Lex Luthor, resulting in him being humiliated on live television and leaves him raging, as well as establishing that Luthor does, in fact, share some of his comic counterpart's pettiness and greed, and despite previous statements to the contrary, isn't above getting revenge when someone actually manages to hurt him. This continues when Superboy, Superman, Cyborg, and Black Lightning also force him to resign from the position of Secretary-General due to evidence found via Terra's earpiece, although possibly due to Joker Immunity, he isn't removed from the Light because of this.
After the controversial Harper/Violet kiss as the show's first romantic LGBT depiction (which was criticized for feeding into stereotypes about attraction between women), "Quiet Conversations" would delve into Harper's background to provide context for her actions, give Violet time to herself to properly address her own identity issues, and provide positive LGBT depiction with the reveal that Kaldur and Wyynde are a couple (helped that Kaldur being LGBT was something originally intended but was meddled by Cartoon Network in the show's initial run) as well as having the two explicitly showing affection to each other onscreen.