In Ah! My Goddess, Keiichi gets turned down by Sayoko, the most popular girl at the college they attend. Once Belldandy shows up in his life, Sayoko starts to get jealous of him and tries to break them up in various ways, with no such luck. In Season 2 she starts to realize her own feelings for him.
Kimi No Iru Machi: Haruto has been infatuated with Nanami all through middle school, and continues despite misconceptions that he's dating Yuzuki, a family friend who moved into his family's home to go to the same high school. He confesses, and Nanami rejects him, because she sees that he's become hung up on Yuzuki. He eventually moves on to Yuzuki, and Nanami soon starts acting rather jealous...
And then Yuzuki moves away, breaks up with him because she can't handle a long-distance relationship, and gets a new boyfriend. Haruto follows her and spends a good while trying to rekindle their relationship, until Yuzuki's new boyfriend dies of complications from a degenerative illness... At which point Yuzuki, who turns out to have still carried a torch for Haruto after all, finds out that Haruto has started to develop feelings for Akira instead.
In Magician's Academy, happens to George and Metallis. George at first is turned off by Metallis' attempts at confessing his love, then the latter falls in love with a girl, Suzuka, and begins aggressively pursuing her. George immediately starts to get jealous and tries to win Metallis' affections, or at least his attention, but ultimately fails at the end.
Naruto Chapter 469 has Naruto's long-time crush Sakura tell him that she's no longer interested in Sasuke and wants to be with him instead. After she spends the entire second half of the chapter trying to convince Naruto that she really means it, he rejects her because he thinks that she still loves Sasuke (which she does). It also shows Naruto's Character Development in that he's not nearly as starved for attention as he once was, and has moved past the Green-Eyed Monster state he was in back when the Love Triangle first developed and he felt inferior to Sasuke and is now a recognized hero on his own.
In Ranma ½, the one time Ranma is interested in Shampoo is during the "Reversal Jewel" Arc, when Shampoo showed disgust at the mere sight of him, however, it passed.
Toradora! has a weird one: Ryuuji and Taiga have unrequited crushes on Minori and Yuusaku, respectively, and team up to help each other. Yuusaku actually started the previous year by confessing to Taiga, but she rejected him without a second glance - now he seems Oblivious to Love. Minori seems the same way (or to simply be The Ditz), but occasionally shows flashes of being anything but. Yuusaku actually moved on to develop his own unrequited crush on his senpai in Student Council, and is too kind to hurt Taiga with an overt rejection. Minori actually shares Ryuuji's crush (sort of) but wants her best friend to be happy. By the end, it turns out that it was really Ryuuji and Taiga who were Oblivious to Love all along.
In Tonari no Kaibutsu-kun, Haru confesses his love to Shizuku but is rejected. Shizuku later begins to regret this and confesses her love to Haru however this time Haru rejects Shizuku.
This happens in Sekai-ichi Hatsukoi. In high school, Ritsu was chasing his Sempai, Saga Masamune. After reuniting a decade later, it's his Sempai turned boss, now named Takano Masamune, that is determined to win him back.
Early on Buffy the Vampire Slayer, Xander had a crush on Buffy. In the comic book continuation of the series, however, she realizes she may have fallen for him, only to find out he's now dating her sister Dawn (who, ironically, had a Precocious Crush on him as a teenager). In this case, though, years passed between the end of Xander's crush and the beginning of Buffy's, during which time they both dated (and in Xander's case, almost married) other people.
In the first issue of Archie Comics, "Pep Comics 28". Archie had just moved into the neighborhood; albeit a couple years younger than he was in later issues and with the nickname "Chic" and tries in his first issue to impress his neighbor Betty Cooper to try to get her to date him through dangerous stunts which she believes make him look arrogant. After Veronica moves in during "Archie Comics 1", the whole dynamic was changed to a Betty and Veronica format where Betty has a really big and sometimes obsessive crush on Archie.
X-23 had a crush on Hellion, who believed she was a mindless, apathetic robot and was not shy about saying so. This was the source of much painful confusion for X-23, and after getting some Character Development, she left the school so she could sort out her trauma. Later on, Hellion (who was just beginning his own Journey Of Self Discovery) went through a Trauma Conga Line in which everything he had once believed about the world was turned upside down, and went off to find her. The comic makes it rather clear that he isn't interested in her out of genuine love, but rather a desperate need to no longer be alone- and once Hellion shows up, a far more confident X-23 rejects him. This probably counts as a Deconstruction.
One Futurama fanfic had Leela realizing her feelings for Fry just in time for him to finally give up on her and date someone else.
In the Homestuck fanfiction Herding Cats, Karkat wrongly thinks this is what has happened between him and Nepeta.
Tavros, who by this point has become incredibly Wrong Genre Savvy, informs Aradia that this is what has happened between them (he used to be flushed for her, she used to be pale for him). Aradia informs him that actually, she was never in love with him, and what's actually happened is that he's now a complete dick.
In Welcome to Silent Hill, Sherlock had accepted that Watson would never love him back. Guess what happens in the epilogue?
Kyon: Big Damn Hero has this in a kind of strange way between Kyon and Sasaki; Kyon had a fairly obvious crush on Sasaki during middle school, but once they go to high school they drift apart and Kyon starts getting involved in, well, stuff. And then she starts being significant to the plot again (and having her own crush on Kyon) once he's gotten himself over his crush he didn't realize he had and was set up in an Arranged Marriage with Tsuruya. He's also involved in his really strange harem-situation with his fiancee.
This trope is quite popular in the Kyou Kara Maoh! fandom, with Yuuri realizing that he's in love with Wolfram after Wolfram has already moved on.
A Growing Affection does this to Sakura; Naruto announces in the first chapter that he is no longer in love with her. By the end of the first book, she is in love with Naruto, but he and Hinata have started dating.
ThisRoy/Ed fanfic deals mostly with Ed being in love with Roy while Roy only wants him for sex. By the end, Roy begins to realize he's in love with Ed after all, but at this point Ed has had enough.
This trope is gaining in popularity for Enjolras×Grantaire fics in the Les Misérables fandom, where it goes under the label "Piningjolras". Levels of IC-ness and quality, as always vary
Harry Potter has a crush on Cho but is fully aware that Ginny has a crush on him. After things don't work out with Cho, and Ginny has already moved on, Harry develops a crush on Ginny after dealing with a bout of jealousy — a Green-Eyed Epiphany — over Ginny's love new interest.
Onegin/Tatiana in the Russian novel/opera/film Eugene Onegin Though Tatiana still loves him, but she's married to someone else now, and he treats her better than Onegin ever did or will.
Central to the plot of Wendelin Van Draanen's novel Flipped, which starts with with a young girl's crush on a new neighbor boy her age (who finds her to be a really annoying know-it-all), shows her feelings changing from said crush to disillusionment as they grow up, and ends with the boy's own growing feelings for said girl going as far as said boy ruining his own social rep among his peers to show how much said feelings have grown.
In Gone with the Wind Rhett doesn't fall for someone else, but he loses interest in Scarlett over a period of some years, as her indifference, mistreatment, and obsessive pursuit of Wilkes wore away at his feelings for her. By the time their daughter Bonnie died, it was mostly over before Scarlett even fully grasped that it had started.
In the Anne of Green Gables series, Anne's childhood friend Gilbert Blythe has a crush on her for about two and a half books. When he finally proposes to her, she rejects him because she isn't in love with him. Near the end of that book, Anne realizes she actually is in love with Gilbert, but she is convinced he is engaged to another woman. Luckily, the engagement turns out to be just a false rumor.
The Russian adaptation of The Shadow by E. Schwartz features this. First, the writer and the princess fall in love, but then the shallow princess abandons him for his shadow. In this variant, the writer survives and defeats his shadow, the princess is once again in love with him, but now he is only interested in Annuncuiata, another girl.
Another Russian Book called Militia Sergeant features this in a classic variant. Nikolaj Zacharow, a young militia officer, and Natasha, a daughter of a factory director, meet, but Natasha wants him to make a caerer, and not be stuck in militia, so she abandons him. Years later they meet, he is already a captain, her love for him comes back, only for him to reveal that he is already happily married and only agreed to meet her to say goodbye.
While not played entirely straight this trope appears in The Hunger Games. By the time Katniss realizes she's in love with Peeta he has been captured by the Capitol. They manage to save him and she expects a very happy reunion. Instead he tries to strangle her because he's been brainwashed into thinking she's a mutation who wants him dead. Ouch.
Live Action TV
The main theme of Season 6 of Bones. Booth tells Bones he loves and wants a relationship with her in the 100th episode, Bones turns him down, they part for seven months, Bones realizes her feelings for him, Booth has a new beautiful Blonde girlfriend, Hannah. Lampshaded in The Doctor In The Photo where Bones tells Booth her feelings for him and he informs her that he has moved on with Hannah now.
Then Bones prompts Booth to propose to Hannah, but Hannah is not ready to settle down. Booth ends up breaking up with her on the spot and then tells Bones that he doesn't want to be in another relationship anytime soon.
In Glee when Emma is in love with Will Schuster. Later, Will finds out that he loves her too. But Emma's already dating this dentist who drives a sweet ride. Then Will tries to woo her by being cool like the dentist. Too bad the dentist is played by John Stamos...
Also works with the whole Finn/Rachel/Jesse situation; Rachel pines over Finn for half of season one. Finn seems to return her feelings, but is dating Quinn. Then when he finds out Quinn cheated on him with Puck, he breaks up with her, and Rachel assumes that she can automatically jump into the place of his girlfriend. He rejects her so he can go out with Brittany and Santana. Rachel quickly moves onto Jesse, just in time for Finn to decide that he has feelings for Rachel. Rachel then rejects him, and he spends the rest of the season trying to get back together with her. They get together in season two, but he breaks up with Rachel when he finds out that she kissed Puck out of spite. She spends most of the rest of season two trying to get back together with Finn, but he's moved onto Quinn, who is dating Sam. Sam breaks up with Quinn when he finds out Quinn kissed Finn. Quinn and Finn start going back out, but Quinn can tell that Finn still has leftover feelings for Rachel. Finn breaks up with Quinn when he realizes that he's really in love with Rachel, who in the mean time has had an episode-long crush on Blaine, who also has an episode-long interest in her (Kurt, of course, has a crush on Blaine), and expressed an interest in Sam. She winds up sort of getting back together with Jesse, only for Finn to kiss her in the season finale, leaving Jesse in the lurch.
Taking the meaning of the word Switcheroo to a whole new level.
Friends: Ross and Rachel do this so many times its unbelievable. S1: Ross —> Rachel. S2: Rachel —> Ross. S3: Ross —> Rachel then Rachel —> Ross. S4 and S5: Rachel —> Ross. S6: Ross —> Rachel. S8/9: They swop per episode. S10: Ross —> Rachel. Phew.
Later in the series it happens again; Joey falls for Rachel, falls out of it, and guess what: she proceeds to fall in love with him. Phoebe even lampshades Rachel's tendency to do this.
Ephram and Amy on Everwood count as he's with Madison when Amy finally decides to be with him.
Hannah Montana : Miley's at first annoyed by Jake's attempts to woo her, but then she falls for him and he's already moved on.
Done interestingly on Dollhouse - Paul Ballard is in love with Echo while Melly is in love with him. Then Echo falls in love with Paul, though they don't consummate the relationship. Then Alpha kills Paul's mind and it's re-made without his love for Echo, though she still loves him anyway. Then in the next ten years they spend together he falls for her yet again and they're implied to have a relationship, but she won't say she loves him. Then he dies. Joss Whedon, you make puppies cry.
Britta rejects Jeff in Community from the very first episode. But when she develops feelings for him (at last), he's with Michelle. Troy also starts to like Annie when she's finally into someone else (Vaughn in this case). The season finale brings a surprise (or not so much) resolution to both cases by finding a common link.
Gilmore Girls has a variant on this: Rory dumps Dean for Jess; Dean longs for her for a while, until he moves on, which visibly upsets Rory. When R&J's relationship is going through a hard time because Jess treats her like dirt, she finds out Dean's engaged. As with many Unrequited Love Switcheroos, they eventually get together ... but not for long.
Scrubs can also be mentioned, in the first season that is: at first JD likes Elliot but it's not reciprocated; after they sleep together, she still likes him but he's moved on; on the third season it's done again: first he likes her again but she's with another guy, then she dumps such guy but JD's not interested any longer. Then, on fourth, she's with his brother and that annoys him and so on...
The Big Bang Theory, though it may not count in full as Leonard was arguably never really into Leslie or Dr. Stephanie as much as he was with them just for the rebound.
But it's played straight in that when Penny breaks up with Leonard and he gets together with Priya, she re-develops feelings for him note Admittedly, this is after considerable brainwashing from Amy, who convinces Penny that Leonard was a perfect boyfriend, who dumped her, not the other way around. In season 5, after Leonard breaks up with Priya, he and Penny get back together. But by the beginning of season 6, Penny is already questioning the future of their relationship.
There's also the on-and-off romance with Bernadette and Howard, which shouldn't being going anywhere considering that they're now married.
Maybe ER a bit, half-way in the series: John's got a major crush on Abby, but she's with Luka; when they break up, she makes it understood that she wants to be with John, but he's already with Susan. Arguably, there's also a bit of that with Ray and Neela later on.
The UK version doesn't fit as well considering that by the time Jim was dating Karen, Pam had called off her wedding and broken up with Roy because of Jim; when Tim was seeing Rachel in the UK Version, Dawn was still with Lee and did not seem to return his feelings yet. Remember how Dawn rejected Tim at the end of the second series? The show never had a switcheroo.
Ah, but in the very last UK office programme, the second part of the Christmas Special, Tim gives Dawn a painting set as a present (because at some point she had mentioned she had always wanted to carry on with her love of painting), which she only opens while on her way back to the airport with her fiancee. A few scenes later she returns to the Christmas party and kisses Tim, stating that she was no longer engaged, which is when the two leave the party together.
Dwight remained hung up on Angela for a long time after they ended their secret relationship, and had even entered into another secret affair with her after she got engaged to Andy. Dwight spent the next several months trying to get Angela to leave Andy and be with him. However, he eventually gave up after learning that Angela had lied about not sleeping with Andy, and that she had been stringing both of them along. About a year later, when Dwight and Angela made an agreement to have a baby together, she realizes she wants to be with him, but he has long since moved on. And now from the looks of things it seems to be happening again in season 9, first he wants to be with her again, but she turns him down because she is still married to Senator Lipton. However, now that her husband has officially come out of the closet and her marriage appears to be over for good, it is heavily implied that Angela still has feelings for Dwight, and becomes jealous when he starts to date someone else. As of the most recent episode the switcheroo is all but confirmed when Angela confides in Oscar that she is still in love with Dwight. In the series finale, Dwight and Angela get married.
Randy and Catalina on My Name Is Earl. After their Citizenship Marriage, Catalina feels obliged to sleep with Randy, but is determined to do it as badly as possible to put him off. Only... afterward, she can't believe how sensitive he was to her, and her behavior in the bedroom has put him off. Said behavior involved rubbing a dead fish on her armpits, hiding it under the bed, and jumping him while saying "Make love to me like your father did to your mother."
Many times with Ed/Carol on Ed. "Carols" go from Nick Stanton to Bonnie Hane to Dennis Martino to Frankie Hector.
Bright/Hannah/Topher and Ephram/Amy/Madison on Everwood.
iCarly A Christmas wonderful life episode where Carly wishes her brother was normal. As part of the changes caused by her wish, Freddie, who has at the very least a strong crush on Carly in the series, has given up on Carly romantically, dating a whiny brat. He also gives her an extreme cold shoulder which indicates their friendship is now non-existent. Carly finds out she is now dating Nevel. Carly pretty much breaks down at the idea that Freddie doesn't love her and that he isn't her friend.
Toyed with in the Torchwood episode "Adam", in which Toshiko stops hopelessly pining after Owen and gets a boyfriend, while Owen suddenly starts pining after her. But in reality, their personalities were changed by an alien who gave them Fake Memories and made himself Tosh's boyfriend. Interestingly, despite having their memories wiped, their relationship did seem to change after this episode, with Tosh going so far as to ask for a date and Owen accepting it. Theneventsintervened.
This is done a few times with Gary and Valene in Knots Landing during the 8 seasons they were seperated.
Dylan and Brenda in Beverly Hills 90210, Brenda breaks up with Dylan after a pregnancy test scare, he spends the next several episodes trying to win her back. Brenda begins to have second thoughts about the break-up right when Dylan begins to become interested in someone else.
For the first two seasons, Andrea has an enourmous crush on Brandon, who (for the most part) only sees her as a good friend. In season 3, Brandon begins to realize his own feelings for Andrea, but by then she has given up on him and began dating someone else.
Early on in Buffy the Vampire Slayer, Cordelia has a crush on Angel, who is in love with Buffy. In season 3 of the Spin-Off series Angel, Angel develops a crush on Cordelia, but by then she seems to have moved on from him and has fallen for the Groosalugg. Like Xander and Buffy, several years passed between the end of Cordelia's crush and the beginning of Angel's.
Also, Wesley seems to finally get over his feelings for Fred just in time for her to realize her feelings for him.
Hyde and Jackie in That '70s Show. After Hyde and Jackie break up, he wants her back, but she clings to Kelso for support, who also still has feelings for her. Eventually she realizes she has to choose between them. By the time Jackie chooses Hyde, he has moved on to somebody else.
Hillary: ...Oh, my gosh, what am I saying? I'm gonna go lie down.
The main character in Psych, Shawn Spencer, spends most of the early seasons trying to go out with Detective Juliet O'Hara, who keeps rejecting him. She finally comes around and admits she like him too, when he's on a date with his high school sweetheart.
Then he breaks up with said girl, but Juliet has moved on to a rich guy they met on a case.
Josh and Donna from The West Wing were constantly on this trope. Josh gets jealous of Donna's random dates in season 2. Then Josh moves on enough to get a crush on Joey Lucas, and Donna gets jealous. Then Donna moves on enough to get involved with Cliff Caley, and Josh gets jealous. Then Josh starts dating Amy Gardner, and Donna gets jealous. Then Donna starts dating Jack Reese, and Josh gets jealous. Then Josh starts dating Amy Gardner again, and Donna gets jealous. And this is all before either of them ever said anything to make their romantic tension anything other than an ambiguous Ship Tease.
ITV's Primeval, in classic scifi fashion, turns this trope on its head with the relationship between Nick Cutter and Claudia/Jenny. Nick and Claudia fall in love by the end of season one. Then Nick goes back in time and accidentally changes time so that Claudia is erased from history. She is replaced by Jenny who looks just like her but has a different background and personality Nick and Jenny start to show feeling for each other, but Nick dies right before Jenny finds a picture of Claudia that convinces her that Nick was telling the truth.
Conner and Abbey's story also has a more traditional switcheroo. Abby rejects all of Conners awkward advances. But when Conner starts going out with Caroline she tries to sabotage their relationship.
Then Conner figures out that Caroline was working for Leek and wasn't really interested in him. He realizes she played him for a fool and turns to leave... Of course, Caroline is suddenly interested in him for real.
This nearly happened in Pushing Daisies. When Olive Snook finally gets over Ned and moves on he begins to doubt that his feeling for her were truly those you would feel for "just a friend".
Castle has feelings for Beckett, but she has on-and-off romances with other characters. He attempts to get together with her at the end of season one, only for her current boyfriend to walk up behind them, and for Castle to chicken out.
Season two finale: Beckett attempts to ask Castle out, only for his ex-wife to show up. The two then head for the islands.
Season three ends with them relatively evening the score, as Castle calls Beckett out on not talking about their Fake-Out Make-Out and telling her that he loves her as she blacks out after being shot.
At the start of season four, she tells Castle she doesn't remember anything about the events of the Season 3 finale. She's lying.
At the end of season four, they start a relationship.
Lizzie McGuire- Throughout the series, Gordo has a crush on Lizzie and she has no idea. One episode reveals that back in the fourth grade, she had a crush on him.
While dating Cady, Sam beings to suspect that she is The Devil's daughter (e.g. flowers and animals die in her presence). He doesn't know he's The Devil's son yet, though, which could indicate that all those things happen because of him.
Mal and Inara from Firefly have an extremely complicated version of this trope. It starts with Mal, and then Inara starts to reciprocate somewhat, culminating in her giving him a kiss out of relief when she had been afraid he died, but of course, Mal was unconscious at the time and didn't figure out it happened. Just when it seems like the two might address the rapidly growing Unresolved Sexual Tension between them, Mal sleeps with Nandi, which causes Inara to completely breakdown and realize she's in love with him but can't do anything about it since she's a Companion, and further motivates her to leave Serenity. In the Big Damn Movie, she returns and it's implied that she might stick around to be with Mal.
Amber and Alfie from House of Anubis. Alfie was well known for following Amber around like a lost puppy for all of season one and part of season two. They did date, but Alfie was still pulling most of the weight and they eventually broke up. Then, as Alfie fell for another girl...Amber grew feelings for him and was now the one chasing after Alfie.
A Girl of the Week tried to pull this one on both Charlie and Alan in Two and a Half Men. Back in high school they had both snubbed her: Charlie because she wasn't pretty enough and Alan because he was just clueless. She went through extensive cosmetic surgery and attempted to seduce them both just so she could then reject them and rub their noses in it. Of course, after seeing how crazy she had become, they didn't count it as much of a loss.
This was the premise of the final season of The Parkers. Nikki spent the whole series chasing Professor Oglevee, who saw her as an Abhorrent Admirer. In the last season, however, she met someone new and became engaged. That was when the Professor realized he loved her after all. After some wedding-day hijinks, the series ended with Nikki and Oglevee finally getting married.
Conway Twitty's "Don't Cry Joni" fits this trope very well.
Anberlin's song "A Day Late" is a song where the singer is giving a Just Friends speech after a Love Confession that came after he had moved on to somebody else.
The Miyuki Nakajima song "Milk 32." "Milk," a guy who works at the bar of the same name that, well, serves milk, is in love with the narrator; however, the narrator only goes to see him when she's just been dumped. One day after being dumped, she comes to visit "Milk," who avoids talking to her and gives her glass after glass of milk to distract her, until finally he leaves. The singer is then left calling for Milk and for her receipt, when she realizes that she actually kind of liked him.
"Sunday Morning" by No Doubt is all about a Bob gloating over how an Alice gets a taste of their own medicine.
You're trying my shoes on for a change.
They look so good but fit so strange.
The Backstreet Boys song "Bye Bye Love" is arguably this trope.
German pop group Die Prinzen's song "Gabi und Klaus" is all about this. Gabi loves Klaus but he doesn't want her anymore. Klaus realizes he makes a mistake, Gabi tells him to get lost.
"Perfect Timing" by Pretty Balanced
She can ignore you as much as she likes, she doesn't like you anymore.
She's fucking gorgeous you can't help but blush. Why didn't you notice her before?
The Doc Walker song "She Hasn't Always Been This Way," couples this trope with She Is All Grown Up, with the guy in the song realising that his friend's little sister—who had crushed on him when she was much younger—is now very attractive and, in the words of the song, "outta my life, outta my reach..."
The point of Stevie Wonder's song "Don't wonder why".
"I Want You Back" by the Jackson Five
When I had you to myself/I didn't want you around/Those pretty faces always made you/Stand out in a crowd/But someone picked you from the bunch/One glance was all it took/Now it's much too late for me/To take second look
"Taken" by One Direction
I slept on your doorstep/Begging for one chance/Now that I've finally moved on/You say that you've missed me all along
Tchaikovsky's Eugene Onegin. The young Tatyana writes a love letter to Eugene, who does not return her affections. It is only after she marries Prince Gremin that he realizes his true feelings for her. She admits that she still loves him, but decides to stay with her husband because he treats her better than Onegin ever would.
Briefly in The Order of the Stick: after Roy's spent time as a woman, he apologizes to Miko for having treated her as a sex object; she expresses interest in him now that he's learned his lesson, but he shuts her down, having realized that she's an arrogant, destructive fanatic and he was only interested in her because he was thinking with the Trouser Titan.
You call it the...
That's not the point!
In Homestuck, Kanaya has a crush on Vriska, who's in love with Tavros. Long after Kanaya "Discard[s] The Preposterous Infatuation" Vriska is punched across the room by Kanaya and promptly swoons over her.
At first, Annie seemed indifferent to Jack's attempt to flirt with her in chapter 31 of Gunnerkrigg Court. Then, by the end of chapter 34, this happens.
In El Goonish Shive, this is briefly shown as one of the effects of a "swish" of a magic wand. No one in universe is aware of any of the effects of the wand because that is how it works.
Lucy of Bittersweet Candy Bowl is the king of this; not only does Mike pursue her for years only for her to keep pushing him away until she accidentally helps get him back with his Long Distance Girlfriend -and- actually manages to convince him that she doesn't actually like him, but Paulo, who has had a crush on her for years, when finally given the opportunity to get with her turns her down (because she is looking for a rebound at the time) and ends up dating other girls instead, making Lucy jealous.
Melissa Hellrune of Eerie Cuties and Magick Chicks is a prime embodiment of this trope. At first, Ace Whiteclaw pined for her affections, but after being blatantly rejected, he matured greatly over the course of the comic and starting dating Brooke. Melissa, on the other hand, was transferred to an all-girls school and now realizes what she missed out on when she initially rejected him.
Leslie and Robin of Short Packed keep switching who wants to have a relationship between them. At first Robin only has her around in a onvoluted plot to get her Straight Gay friend and Leslie actually liked her. Eventually Robin reciprocated her feelings but Robin cheats on her when on a massive sugar high. Robin wants to get back together but Leslie doesn't want to despite still having feelings for her. Then Robin mellows into someone Leslie could have a relationship with and she gets together with her old friend.
Happens in The Guild after Codex breaks off her "fake relationship with a fictional version of Fawkes," who normally only does one-night stands. However, to the latter's surprise, Codex proves "interesting," so he makes an attempt to pursue her further, only to be told off.
Although nothing's certain until Season 5, this also seems to happen with Codex and Zaboo, after Zaboo finally (mostly) gets over Codex at about the same time she concludes (privately) that he passes her "litmus test."
It's confirmed now.
Danny Phantom started off with Sam giving off most of the romantic vibe towards Danny who remained clueless for the most part. When Sam started dating someone else, Danny starts to realize by end that he likes her. They eventually get a Relationship Upgrade.
Largely the plot of the "Arnold Loves Lila" episode of Hey Arnold!. When Lila believes Arnold has a crush on her (thanks to Helga's hastily re-written "Arnold loves Helga Lila" graffiti), she starts to like him too, but he "likes her, but doesn't LIKE-like her". Once she gets the message, he really does start to "LIKE-like her," but too late; now she'd rather be friends.
There's also the "Arnold Visits Arnie" episode where Arnold meets bizarro equivalents to characters in his own neighborhood, including "Hilda," a seemingly well-adjusted Helga he is immediately attracted to... who has a thing for Arnie. Meanwhile Arnie's girlfriend "Lulu" seems more interested in Arnold than her real boyfriend...
The thing is, in the bizarro universe, the one-sided love square is reversed. In the normal world, Helga —> Arnold —> Lila —> Arnie —> Helga, whereas in the bizarro world it's Hilda(Helga) —> Arnie —> Lulu(Lila) —> Arnold —> Hilda(Helga).
Family Guy: 8 Simple Rules for Buying My Teenage Daughter: Meg becomes interested in Neil (who had been obsessed with Meg) only after she realizes he has a girlfriend.
Undergrads, Nitz develops feelings for Jessie after seeing her naked... for exactly one episode. Prior to this episode and in every episode following, she loves him but he has no interest in her. Which makes her blowup at Nitz in the finale about not noticing her feelings rather silly since he openly said he had feelings for her...
The one episode where he showed interest in her she rejected him because his approach to her was completely wrong, mostly by just acting like they're already a couple.
Played for Laughs in the Fanboy and Chum Chum episode "Fanboyfriend". Lupe, a Huge Schoolgirl falls for Fanboy after he... er... saves her from a spider. For most of the episode, Fanboy tries to make Lupe understand that he is not interested - but at the end of the episode, after Lupe gets radioactive superpowers, the feelings are flipped.
Kaeloo and Mr. Cat have this happen rather frequently. Who's crushing on whom depends on the episode.
Although the ending makes it ambiguous as to whether PB gets a Green-Eyed Epiphany as a result or not.
Mako and Korra in The Legend of Korra. Korra starts crushing on Mako, but he rejects her when she asks him out since he's dating Asami. Then, he gets jealous when he sees her with his brother Bolin and the two let the issue drop until later on in the season when Asami finds out Korra had a crush on Mako and then she starts seeing that there are still sparks between the two. By the season finale, Mako breaks up with Asami and confesses that he's in love with Korra, who reciprocates it.
Truth in Television, anyone can relate to this trope at some point or other. The French even have an expression for this common situation : "Je t'aime, moi non plus" (literally : "I love you, neither do I")