This trope is when a plot point, story element, character arc, or relationship arc is methodically taken apart, reset back to something resembling the status quo ante, and advanced over and over again. It can seem like the writers have realized that they cannot successfully take a series past its basic premise, so rather than provide any long-term resolutions or adapt the plot, they keep putting the characters back where they were before and forcing them to learn the same lessons, go through the same Unresolved Sexual Tension, or fight the same Tournament Arc that they did last season.
This is distinct from Negative Continuity in that in the latter there is no expectation that the series' plot will advance. The Yo Yo Plot Point occurs within continuity and is frequently all the more glaring for that fact. After all, there are only so many times that the same relationship can break up or the same character can attempt to go to college before it gets silly.
Note: This trope is not about plot points that get dragged out long past when they should have been resolved. This is about plot points that are resolved, and then un-resolved, repeatedly.
The Yo Yo Plot Point can be an Enforced Trope in a popular series that is intended for a very specific demographic; after all, True Love Is Boring to the target audience of Shōnen. In this case, watch out for Creator Backlash or a continually rotating stable of writers. Related, when a series changes writers, sometimes the new folks want to revisit plot points from previous arcs and deliberately reset their predecessors' work. If it happens over and over again, it can seem like this trope to the audience.
Post Script Season is related, but typically happens only once. See also: Status Quo Is God, Failure Is the Only Option, Sequel Reset, Heel-Face Revolving Door, Aesop Amnesia, Once an Episode. In comics, Joker Immunity and a Cardboard Prison are often employed so that villains may be defeated many times over.
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Anime and Manga
Ken Akamatsu, writer of Love Hina, should really have known when to cut a long story short. Most readers figured out pretty quickly just who Keitaro's "promise girl" was, and the plot itself answered the question in the 10th of 14 volumes. So throwing in umpteen further "complications" to spin out the romantic tension ("Is she really the Promise Girl?!!") for its 14-volume run wasn't really effective, especially since he and Naru outright admit that they no longer care if she really is the girl in volume 12 and finally kiss. The same thing happened with Keitaro's TokyoU career: he was accepted after the second year of the story, but in order to keep the protagonist's educational prospects as a source of tension, Akamatsu had a large bell fall on top of him, preventing him from taking up his place there, though it did result in him taking a level in badass in the meantime. Considering that Akamatsu is obviously a Rumiko Takahashi fan, we should be thankful that he ended the manga after 14 volumes instead of 45.
Kira and Rei of MARS are supposed to be "rescued" by each other's love. However, pairing them up early in the story just won't provide the Wangst-fuel for fifteen volumes, so the comfort and stability (and Character Development) they create for each other is constantly tested via Expansion Pack Past. The result is that they seesaw between "well-adjusted individuals" and "pair of head cases" as each trauma comes to light, with the unaffected partner having to rescue the victim all over again. With Kira in particular, the pattern started veering away from tragic and towards ridiculous, and issue upon issue was heaped on her. By the end of the story, there doesn't seem to have been a torment that she hasn't suffered.
Poor Sora of Kaleido Star is a living yoyo: no matter how hard she works, no matter how spectacular a performance she turns in, at the end of each Kaleido Stage production she falls back to the bottom of the pecking order and has to work her way up all over again. It's only at the end of Season One that she's acknowledged as the true prima donna of the stage... whereupon the show got a sequel, and a Post Script Season saw her "star" status usurped yet again.
Early in the run of Marmalade Boy, protagonists Miki and Yuu find their slowly-developing love to be threatened by new characters, love triangles, and typical rom-com misunderstandings. Fortunately, love wins out, and they remain together in the end. This happens again. And again. And keeps happening. It seems that you simply cannot add another new character or event to the story without having Yuu and Miki (especially Miki) question the other's already-proven affection. In fact, a few episodes before the end of the anime, Miki herself admits that she's tired of the constant doubt and worrying and calls off the whole relationship. This is later resolved, but you can't help but agree with her.
For a non-romantic example, there's InuYasha. While the romances are definitely of the "will-they/won't-they" variety, the true culprit is the main plot of killing Naraku. They get close, then he escapes. InuYasha gets a new attack that makes it possible for him to kill Naraku. Naraku levels up and defeats it. Rinse and repeat for way too long.
This plagues the elongated conclusion of the 4th World War arc in Naruto. At this point, most readers have lost count of how many times during the climactic battle Naruto's allies have come to doubt their usefulness, then overcome their doubt by resolving to do their best regardless, then soon fell prey again to that same doubt; how many times the Big Bad has wavered towards doubt in his philosophy, then back to absolute faith in it and trying to make Naruto doubt his philosophy, and then back again; how many times, conversely, Naruto himself has felt the need to go through a revelation of why his ideals are worth believing in and fighting for, prompted by him relating to his possibly-Love Interest, Action Dad and Rival Turned Evil each in turn, only for his resolve to soon waver enough that another revelation is in order; and how many reveals of either the good guys' or bad guys' seemingly unbeatable "True Power" there have been, only for that power to be beaten soundly, trumped and superseded, followed by ominous hints of the next Ultimate Power That Will Surely Decide Everything.
Rogue and Gambit of the X-Men are notorious as victims of this trope. Even more so than Scott and Jean, writers seem to have a dislike for giving them any kind of stable love life. Several issues were promoted as "the one where Rogue and Gambit finally get together!" but any long-term reader will realize that this will only last ten comics at best before they split up again, for increasingly ridiculous reasons. And then the chase will start all over again. Gambit lampshades this in X-Men Legacy, explaining to Rogue that he doesn't even get jealous anymore because she'll always end up back with him eventually.
And this is all alongside someone deciding they want to put their "once and for all" stamp on Gwen Stacy's clone(s) (which would be three or four since the mid-90s).
Batman was put through the wringer, in a multi-month multi-title event, and came out of it promising to be less of a jerk to his friends and allies in the future. Didn't last.
Main plot of Strangers in Paradise is lengthy will-they-won't-they relationship, and so are several main subplots. That reasons for this yoyoing are more realistic than in other examples doesn't help, because they go back and forth just too many times. One plot that isn't romantic features organization "The Big Six" repeatedly pursuing the main character. Each time the story resolves with the leader of "Big Six" dead and the organization seemingly dismantled, or at least promising to leave main characters alone. However, each time it soon turns out that "The Big Six" still exists and one of ex-minions, now promoted into the big boss, decided to continue pursuing the main character for various reasons.
The Martian Manhunter is ridiculously powerful, his only vulnerability is fire, and unlike most superheroes with weaknesses, his origin doesn't contain a particularly good reason why he's vulnerable to fire. Those facts combine to ensure that every time a new writer gets a hold of him, they come up with the "real" reason he's vulnerable to fire and (since they usually decide it was all in his head the whole time) usually have him overcome it for good. Again. Until next time.
Professor X of X-Men fame has an autistic son - David Haller, a.k.a Legion - with tons of superpowers and multiple personalities, some of which are evil. He's too unstable to be a superhero, so when he turns up it's almost always in the position of "villain-who's-really-a-victim." But he's basically a good kid, so every time he goes berserk he has to have a mental breakdown first. And since he's a sympathetic character, his stories have to end with him "finally getting the help he needs." In other words, virtually every David Haller story is: Legion has a relapse/Legion goes on a rampage/Legion is subdued/Legion is cured. Wash, rinse, repeat.
During the Marvel NOW! run of X-Men Legacy, it's revealed that he did get help, and it did work... until Xavier died, and all of it was undone. Still, he is much better off than he was before.
Fantastic Four has a few stock plot points that tend to repeatedly cycle. A) Johnny learns to act mature, B) Ben learns to accept his appearance, and C) Reed learns to appreciate his family and not shut them out. They can usually be relied to forget these lessons whenever the book changes writers.
Raven of Teen Titans seemed to have found peace after she defeated her father in the "Terror of Trigon" arc, but she wound up infected by his influence again in the early '90s. After her corrupted body was destroyed, she seemed to be free of evil (even if she was stuck in a golden spirit form). Flash forward to Teen Titans volume 3 and on, where the resurrected Raven had to fear being corrupted yet again by her father, who was inexplicably resurrected himself in Judd Winick's run of "Titans". The plot point of Raven going missing and having to be found or rescued was also recycled twice within volume 3. In the New 52 reboot, Raven's back to trying to fight her father's influence. Writers also seemed to constantly recycle the "will they or won't they?" question about her relationship with Beast Boy, seeming to settle on the two getting together before everything was rendered moot by Flashpoint.
Harry Potter: Harry is loved by all, Harry is despised and ostracized. Specifically, separate events in years 1, 2, 4, and 5 tarnish the attitude of Hogwarts students toward their local celebrity, but his reputation is usually fixed by the end. (In year 7 he becomes "Undesirable Number 1" after the bad guys take over the government and the school, but it's not as clear what the general opinion of him is.)
Zoey's Unwanted Harem problems in The House of Night. The first couple of books had her being torn among her boyfriend Erik, her jock ex-boyfriend Heath, and poetry teacher Loren. The third book resolved the love polygon, albeit in an abrupt and contrived way that brought into question Zoey's intelligence, by having Erik leave Zoey after she slept with Loren which severed her blood-based connection with Heath and then Loren turned out to be working for the Big Bad all along and was killed off at the end of the book with the clear message that Zoey had learned her lesson and would work hard to repair her broken relationship with Erik. But then the fifth book brings Zoey's Unwanted Harem right back with her renewing her blood-based connection with Heath thanks to a contrived "you need to drink his blood or else he'll die" situation (and making their connection even stronger than it was before) and getting a Replacement Love Interest for Loren in the form of Stark. To top all this off, Erik is derailed into a possessive jerk to justify why Zoey is suddenly going back on her earlier vow to stick to just him, and she proceeds to repeat the "woe is me, I'm a ho for being unable to choose between three hot guys" indecisiveness/wangst from the second and third books all over again. The sixth book appears to try resolving at least one factor of this love issue for good by killing Heath off, only for the very next book to reveal that he's not so dead after all and Zoey proclaims her love for him, even though she's still stringing Stark and Erik along. Romantic Plot Tumor doesn't even begin to describe it.
The Bloody Jack novels have this in a bad way. Since Book Two, every single book has Jackie wind up in trouble with the law, be separated from her "true love", Jaimy, land in some kind of Attempted Rape / Virgin Tension scene, and flirt and make out with at least one attractive young man (or, on occasion, an attractive young woman). Usually, by the end of the book, the troubles are sorted out and Jackie and Jaimy are/are on the brink of being reunited—and then a new problem tears them apart.
Live Action TV
Gilmore Girls: This proved to be a huge problem in the latter seasons with Lorelai and Luke. After five years of will they or won't they, Lorelai proposed to Luke at the beginning of season 6 and he accepted. Instead of dealing with the myriad other potential plots the show had going on at the time (namely, the fallout from Lorelai and Rory's estrangement), a long lost daughter was introduced who literally served no purpose other than to break up Luke and Lorelai and send Lorelai into a quickie marriage with old flame Christopher which in turn served no purpose other than pushing Lorelai and Luke getting together "for good" back to the series finale.
Especially irritating as going ahead with the marriage would have opened up a ton more storylines (moving in together, having children, Lorelai getting pregnant, Rory getting a sibling, more drama with the parents etc.) and everyone, including Rory, knew Lorelai and Christopher were terrible together making Lorelai look like an idiot for going back to him yet again.
Soap Operas - thanks to their never ending nature, decades on the air, and poor quality of writers at the helm of most - suffer greatly from this. True, it was never uncommon for super couples to get divorced and remarried several times over. However, it seems like these couples divorce and remarry each four or five times over the course of ten years. Problem is, the things that break the couples up in the first place are never addressed or rectified. It's usually some variation on Your Cheating Heart, however.
Egregious example alert: On General Hospital, Carly Benson and Sonny Corinthos have been married... and divorced... four times. In the past decade.
Ross and Rachel, who got together and split up multiple times over the course of Friends, are a perfect example.
Averted, however, with the Chandler/Monica relationship. Once they got together, they stayed together, and their relationship evolved realistically in a way that benefited the show.
How I Met Your Mother: Ted and Robin's relationship. The first episode ends by saying she's not the mother, the first season ends with them getting together, they break up, they relapse, they wind up living together, have a Friends with Benefits thing going on for a bit, she dates Ted's best friend Barney for a while, then Ted realizes he wants her back... a minor theme of seasons 6 and 7 has been the strain of Robin being best friends with two of her most serious exes, with hints that there's still something between her and Ted. This seems to be solved for good, as Robin and Barney are confirmed to be married and the series will be ending soon.
Robin's dissatisfaction with her career in Season 4. There was a pattern of Robin hating her current news reporter job, quitting it, discovering a supposedly-awesome job...and the cycle repeats with that job apparently being terrible too.
Buffy had a She's Back moment once a season, minimum, usually in the final episode. Every time she "accepts" being The Chosen One, you just know she's going to backslide.
Also, Xander and Anya are in love and having sex on a constant basis, then Xander proposes, they spend the entire sixth season bitching and moaning about it, then Xander leaves her at the altar, Anya goes back to being a vengeance-obsessed demon, and by season seven, they're back to having sex, and Anya commenting about it in her awkward manner.
Xander would regularly have episodes in which he would come into his own, demonstrate that years of facing eldritch dangers without superpowers implied something about his competence and courage, and put his Butt Monkey status behind him. ("The Zeppo", "Graduation Day", "The Replacement", etc.) It never lasted. (Though he seems to have gone back in that direction in the Season Eight and Nine comics.)
Lois and Clark had it bad too, marrying the eponymous characters twice before they finally married for real. (To the point where the actual marriage episode was entitled "Swear to God, This Time We're Not Kidding.") At least one of the marriages involved the Frog eating clone of Lois Lane. Yeah...
Earlier on in the series, before Lois knew that Clark was Superman, the scenario came up repeatedly in which Lois would bring up something important to their relationship, and every single time, at the worst possible moment, Clark would have to become Superman and perform some rescue, which made it seem like he was blowing her off and avoiding the subject.
LOST's love triangle between Jack, Kate, and Sawyer. Kate just keeps bouncing between those two guys like a ping pong ball well into the fourth season. Lampshaded when she leaves Sawyer for Jack yet again, and Sawyer doesn't react at all, telling her to her face that he knows within a few days she'll have found some reason to get mad at Jack again and come back to him.
And later after Jack and Kate get off the island, their engagement ends when it's revealed that Kate has been covertly fulfilling some promise to Sawyer, even though he got left behind.
In its short time on the air, even Firefly had one of these: The status of Simon and River on Serenity. Were they crew, or were they passengers? It fluctuated wildly from episode to episode, and even into The Movie.
Some of it may have been because of order issues and misaired episodes...but it's fair.
In Grey's Anatomy, the whole Meredith/Dr McDreamy thing - they're together, then she wants him but he doesn't want her (although he secretly does), then he wants her but she isn't sure whether she wants him or not.
Scrubs has POV character JD, each of whose (very short) relationships mirrors the last one, contrasted by just about any other main character, all of whom go through some serious Character Development over the course of the series.
Not to mention the number of times JD and Elliot get together, then break up, then... well, you know the drill. There was a joke about in the first 3 seasons that JD and Elliot have sex again once every year. This was dropped after their 3rd breakup, though it was revisited at the end of season 7. When they finally got back together, Jordan lampshades this and says that after 7 years no one cared about it anymore.
Supernatural has major yo-yo-ing going on, enough to make it borderline Narm at times. The cycle is as follows: Sam (or Dean) has an issue but won't talk about it. Dean (or Sam) knows something is wrong and keeps pushing Sam (or Dean) on it, only to be frozen out. Tension builds. Sam (or Dean) keeps secrets. Dean (or Sam) finds out about them. Finally there is a huge fight and Sam (or Dean) walks out. An episode follows where the two of them are seen going their separate ways. Then they realize the importance of family and get back together, and the cycle is renewed. (Notice how the original issue that caused the whole thing never actually gets addressed...)
The writers appear to have noticed this, since they've been easing up on that a bit recently, specifically after Bobby's death in the middle of season 7. They still lie to each other and do crap behind each other's backs constantly, but they're much quicker to forgive because they both know the other has good intentions.
Another example would be how there always has to be something wrong with Sam. It started with his Psychic Powers in the first couple seasons, then his increasingly Jerk Ass behavior in the third season. In the fourth and fifth seasons, his drinking demon blood and the effects it had on him. In the sixth season, he was a Soulless Shell for the first half and had his Hell-wall for the second half. In the seventh season, he had the fallout from the Hell-wall coming down (mostly limited to hallucinations of Lucifer). In the eighth season he started getting sick as part of his trials to close the gates of Hell. And finally in the ninth season, he is tricked into allowing the angel Ezekiel to possess him in order to heal him from the damage done to his body for failing to complete the trails. Most of the time these events are only marginally connected to the main plot, and most were either solved with a Deus ex Machina or just quietly forgotten about once the arc was over. This is infuriating because it both implies Sam is not inherently interesting as a character and must always have something wrong in order for the audience to care about him, and because Dean has never gotten such an arc (minus a few self-contained Monster of the Week episodes) leading to accusations that Sam is favored by the writers.
Nip/Tuck: lives on this trope in the later seasons. Characters from previous seasons whose plot threads seem to have been resolved are brought back in with the magic words "Previously On Nip/Tuck."
Heroes. Claire's relationship with her adoptive father and her power is pretty much like this. In the first season it was believable. But every damn season, it's like she just found out she can heal and has a secret agent as a father. By the time she reconciles with the fact, it's time for her to start freaking out again.
SYLAR'S DEATH. Apparently Killed Off for Real in Volume One. Recovers from his fatal chest wound in Volume Two, but without his powers. Then gets his powers back. Then, in Volume Three, steals Claire's power and becomes immortal - but aha! All powers get switched off during the eclipse, so he finally dies then - but, whoops, as soon as the eclipse is over his dead and decomposing body heals itself and he returns to full strength. He gets Killed Off for Real at the end of Volume Three, because his power can't save him when you stab him in the back of the head and drop a burning building on hi - oh no wait, according to Volume Four, it can. Then he gets effectively 'killed' at the end of Volume Four when his mind is erased and replaced with the mind of Nathan Petrelli. Volume Five rolls around, and this is promptly retconned to his mind being still alive inside Matt Parkman's head - and then he takes Parkman over and even eventually gets his own body back. So Parkman traps him down and does the next best thing to killing him - imprisons him inside a personal Hell and bricks him up in a basement. This lasts maybe all of an episode before Peter Petrelli breaks him back out. Luckily, as part of the Heel-Face Revolving Door thing Heroes seems to love so much, he turns out to have repented while unconscious, and was last seen alive and well, again, but now a good guy. Had the show not been cancelled, this would undoubtedly have been changed back to his usual evil self before long. Also, he probably would have died some more.
The show suffered from a bit of this with the Chase and Cameron relationship. They sleep together, nothing happens, they start sleeping together regularly, Chase decides he has feelings, Cameron rejects him repeatedly, they finally start dating, move in together, get married... then get divorced. Seemingly finally resolved as they wrote Jennifer Morrison out of the show (almost) entirely.
The show seems to be averting it with House himself. Surprising many fans, after his stint in a psychiatric hospital House managed to go the entirety of Season 6 without going back to Vicodin, even right up to the last moment of the season finale when he chooses Cuddy over pills. This comes after repeated failures in this area over the course of the series, and his repeated Off The Wagon moments are actually a pretty realistic depiction of drug addiction and relapse.
For a long time, this was the best way to describe House and Cuddy's relationship. They would get together, break up, sleep together, decide to be Friends with Benefits, actually become an Official Couple again, break up, and repeat. The cycle was broken eventually; House and Cuddy broke up (again), and decided they were Better as Friends.
Queer as Folk: Brian and Justin's relationship is a bit like this, as they break up and get together again about once a season. Of course, being Brian and Justin, it's never quite resolved even when they are together.
Party of Five Charlie and Kirsten. They have a Will They or Won't They? thing going on in season 1, they get together, he cheats on her and they split up until reconciling near the end of the season. They plan to get married in season 2, Kirsten leaves him at the altar and they get back together in the season finale. In season 3 they split up due to her depression and she ends up marrying someone else. That husband leaves in season 5 and they reunite again. Thankfully the first episode of season 6 is their wedding and the drama is finally resolved.
Julia and Griffin. She cheats on Justin with him, eventually getting together until he goes off to military school, then gets back with Justin but they split by the end of season 2. At the start of season 3 she starts right back up with Griffin but then they go through more relationship drama in season 4 and split up again. Then seasons 5 and 6 have a regular thing of her getting jealous whenever he shows interest in another girl.
Star Trek: Thanks to multiple writers and a poorly fleshed-out character background, Spock'sability to lie and lack of emotions tended to bounce around from episode to episode, with some of them determining that his emotions were always on the verge of constantly boiling over and others treating him as an automaton with a physical inability to tell a fib. The writers attempted to resolve this long-running subplot in the Motion Picture and its sequel, where it is fully established that Spock has embraced his human side just in time to make a Heroic Sacrifice at the end of the movie, cleaning and wrapping up his Character Arc... And then they brought him back in the next film and it turns out he has forgotteneverything he learned.
The rest of the series were even worse about this. While The Original Series and Next Generation often portrayed Vulcans as cracking jokes (deadpan, of course) and, though keeping to logic, experiencing and understanding emotions (though of course this varied within the show), Tuvok would never joke, would say he had no emotions and often said he had never experienced emotions. This last part was contradicted when the writers decided he'd had a bout of emotionality as a boy and had to be taught how to control them.
Averted in Frasier: after seven years of Will They or Won't They?, Niles and Daphne finally got together in the season 7 finale. However, in the beginning of season 8 it looked like the writers were gonna use various plot elements (mainly Niles' ex-wife Maris) to stop them from actually being together. Thankfully, though, these issues were resolved in a handful of episodes, and the writers managed to integrate Niles' and Daphne's relationship into the series for its final four seasons.
On Boy Meets World, Cory and Topanga have three major breakup arcs after they first officially get together at the start of season three, and two of those arcs happen after their relationship was retconned into being life-long true love.
On Glee, Rachel and Finn are supposed to be the Official Couple, but they've fought and broken up and gotten together again numerous times, and are generally much less stable and mature than almost any other couple on the show.
Mad Men: Don Draper's Dick Whitman past comes back to haunt him in some way once a season. However, in a case of Tropes Are Not Bad, the recurring nature of the Dick Whitman problem makes perfect sense. Truly facing and dealing with this landmine secret (stealing another man's identity to commit desertion during wartime) would likely destroy the life he built for himself, a tall order for anyone and especially someone with Don's hobo like inclination to run when things get tough.
Veronica Mars in everything pertaining to the title character's various love interests, and most of all her on-again-off-again relationship with Logan, which induces half of the yo-yo-ing in her other relationships to begin with. The two of them go through a constant cycle of fake-outs, second thoughts, setbacks, deal-breakers, revelations and reconciliation, spanning the entire series from act 3 of season 1 going forward. There's a reason this show reruns on the Soap Opera Network.
On Smash, the person that will play Marilyn Monroe in the Show Within a ShowMarilyn: The Musical (later Bombshell) kept flip-flopping from episode to episode, in fact within episodes sometimes. First Ivy, then Karen, then Ivy again, then Karen, then Rebecca, finally Karen. Halfway through season 2 it flips to Ivy again.
The Big Bang Theory: Leonard and Penny have been through a few breakups and keep running into the same exact same problems in their relationship. Most of time it's due to Penny feeling insecure due to her and Leonard being too different (particularly their different levels of intellect) and her being afraid of committing.
The Warcraft series (and especially World of Warcraft) is slowly starting to suffer from a case of this when it comes to the relations of the Alliance and the Horde. They're at war? Not anymore. Oh wait, now they're fighting again... And here comes the next excuse for them to ally with each other!
Finally gets resolved in To Boldly Flee, where his shitty life has got him so broken that he's all too willing to fly into a Plot Hole and make a Heroic Sacrifice to become the universe and finally be happy.
And now that he's back, up goes the yo-yo in Son of the Mask, where he's been reduced to looking through garbage for his latest review fix, blames the audience for it and sob-begs the devil to please kill him because he can't take reviewing life again, once more.
The Simpsons: Marge tiring of Homer and considering leaving him in more recent seasons.
Addressed in the movie where Marge does leave Homer after being unable to put up with his selfishness, ignorance, and shenanigans. Naturally, they do reconcile at the end.
Any episode involving Moe.
King of the Hill in regards to Bobby being accepted by Hank despite his eccentricities. They would repeatedly find something to bond over, only for the next episode to have them again not seeing eye to eye.
The Series Finale contains such a plot, but its frequent use in earlier episodes removes the sense of closure from the episode.
Total Drama Island and subsequent seasons are chock full of it, especially when it comes to character development; they're very Reset Button happy. Things that seem to get resolved as many times as the writers need them to include Heather's Defrosting Ice Queen progress, Gwen and Trent's relationship and later the Courtney-Duncan-Gwen love triangle (possibly resolved at the end of "World Tour" but unclear), Lindsay becoming less of a ditz, Bridgette and Geoff's relationship, Cody's unhealthy crush on Gwen, and constant fluctuations between disdain and respect for Sierra.
Duncan and Courtney's relationship is a particularly bad case. After spending half of Season 1 in Will They or Won't They?, the season ends with them (somewhat) happily together. Then Season 2 comes along and Courtney breaks up with Duncan, but they get back together in the finale. Then they break up again in the reunion special only for them to get back together in the same freaking episode. Finally, they seem to have broken up for good in Season 3, but, as mentioned above, we can't be certain.