Before the crisis, the character is perfectly fine being Just Friends or totally platonic bickering partners with another. But then, that other character gets romantically involved with an interloper, causing their not-at-all love interest to suddenly feel the sting of their absence. Once they finally admit to themselves their feelings, the Romantic False Lead's got hell to pay.
In some works, this is the cue for a Relationship Upgrade. In other works where Status Quo Is God, the envious one will stubbornly refuse to come clean and revert back to her "friend" self once the romantic complication is out of the picture. It's a Aw Look She Really Does Love Him moment—but a hidden one. This arc is especially common when the jealous one is a Tsundere.
Sometimes this trope comes into play after a couple has broken up, with one side having convinced herself that she's over him, until seeing her ex with a vixen causes her to gnash her teeth.
If one partner isn't in denial and deliberately stages such an incident to make the other jealous and admit her feelings, he's pulling an Operation: Jealousy. Sometimes overlaps with Unrequited Love Switcheroo—a flip between which lover's love is unrequited. The writer might need to Derail The Love Interest if the new love is working out too well for the plot to continue.
- In Itazura na Kiss Naoki Irie finally comes to terms with his true feelings for Kotoko Aihara after he hears that her longtime friend Kinnosuke proposed to her. He confronts her and tells her that he doesn't want her loving anyone else. The pair share their first honest kiss and get their Relationship Upgrade. It only gets better from there.
- Tomari in Kashimashi: Girl Meets Girl admits her feelings for Hazumu only after she catches her kissing with another girl, Yasuna.
- Ranma ½: Multiple times, both ways, between Ranma and Akane, Ranma and Ukyo, and Ranma and Shampoo.
- In Samurai Pizza Cats, Polly constantly denied her feelings for Speedy, insisting they were "Just Friends"—even though she constantly got jealous of the time he spent with Lucielle. She even said she didn't like him, he was too goofy in the final episode. It took him almost dying trying to destroy a comet that she finally realized her denial and that she, in fact, loved him. They get together in the end.
- In the anime version of Angelic Layer, Tamayo treats Kotaro only as a close friend until he develops obvious feelings for protagonist Misaki.
- In the Lovely Complex manga and anime, Otani has never been able to see Risa as anything other than a friend...until she's suddenly swooning over Maity-sensei.
Otani: You're always saying "Maity this, Maity that"!! That's why I'm so annoyed!!
Riza: ...Why should you be annoyed?
Otani: How should I know? Annoying things will, of course, annoy me!! Don't ever mention his name again!!
- Inuyasha: Happens in both directions between Inu-Yasha and Kagome, with Koga as Kagome's Romantic False Lead and Kikyo as Inuyasha's Psycho Ex-Girlfriend back from the dead.
- Kenichi: The Mightiest Disciple: Miu constantly denies that she has any interest until Kensei Ma's daughter Renka shows interest.
- Tomoe from Kamisama Kiss is a regular ass to the heroine Nanami 95% of the time but should another man so much as even talk to her watch out.
- Elizabeth of For Better or For Worse had this problem: one plot arc involved her breaking up by proxy with Anthony before the school dance, only to get insanely jealous when her friend felt sorry for him and opted to take him instead. Infamously, this plotline was later echoed and writ large when Anthony got married and Liz lamented that she should have been the one he chose instead.
- Harry Potter
- In Harry Potter, Ron and Hermione have a textbook Slap Slap Kiss going, but Ron is in complete denial about it until Hermione goes to the Yule Ball with Viktor Krum. He's still in denial after that, too.
- It happens to Hermione, as well, when Ron begins "dating" Lavender in the 6th book.
- Later in The Half-Blood Prince, Harry realizes he has feelings for Ginny when he sees her kissing Dean.
- Emma: The titular heroine's best friend Harriet confesses she is in love with Mr. Knightley. It instantly comes over Emma like a thunderclap that she is in love with Mr. Knightley!
- The Princess Bride: The attraction that sparks off the jealousy is one-sided, but Buttercup first realizes that she's in love with Westley when the Countess Rugen starts ogling him.
- J.R. Ward's Black Dagger Brotherhood series uses this trope in Lover Awakened. Zsadist is forced to realize he's bonded with Bella when his brother-in-arms Vishous provokes him. Basically, Vishous acts like he's going to go after her, at which point Z tackles him in a jealous rage, and Vishous explains to Z that he's invoking this trope while being strangled.
- At the start of the Dragonlance Chronicles, Tanis Half-Elven dumps his childhood sweetheart, the elven princess Laurana and tells her he is in love with another woman, Kitiara. It is only after Elistan starts sniffing around Laurana that Tanis realizes he does still have feelings for the elf maid.
- Amelia in Vanity Fair.
- In Mockingjay, Gale reveals that he didn't realize he loved Katniss until another guy flirted with her.
- In The Dresden Files, Harry first realizes and admits his feelings for Murphy after she went on a romantic trip with Kincaid and Harry felt like he wanted to kill him.
- In General Hospital, for geeky Spinelli and fashionista Maxie, it took the arrival of similarly geeky Winifred for Maxie to realize her feelings for Spinelli. And then she slept with Johnny. Hey, it's a Soap Opera.
- Subverted in Better Off Ted. Linda tried to induce this by introducing Ted to her ex-boyfriend... but he and Ted hit it off and become friends. Then Ted pretends to hate him when he realizes Linda was only trying to make him jealous.
- Smallville: Clark and Lois did this with each other often, until they finally hooked up in Season 9.
- Castle: This trope is the bread and butter of the show.
- In Fawlty Towers, Basil and Sybil appear to have nothing but contempt for each other; however, Sybil gets very upset, when she thinks that Basil is pursuing a guest in "The Psychiatrist", and Basil frantically tries to prove that he isn't.
- Community: Although Brita constantly insists she has no feelings for Jeff, she ends coming to terms with her feelings when Slater attempts to renew her relationship with him.
- This is also subverted when Annie attempts to get Rich to join their study group. Jeff is seemingly jealous because of his feelings for Annie, but it's later revealed that he was being apprehensive simply because he hates how perfect Rich is, and once to learn how to manipulate others with similar perfection.
- iCarly: Sam, if her actions at the end of "iSpeed Date" were meant to indicate her feelings for Freddie. Carly might end up doing the same in a future episode.
- Teased a few times with Josh and Donna on The West Wing, but hammered home on Donna's part when Josh starts dating Amy Gardner.
- In the series Eva & Adam, about middle-schoolers in love in Stockholm, Eva only realises she likes the new boy Adam when her best friend seems to say she may be interested in Adam.
- NCIS: In the oft teased Tony and Ziva relationship, the two will usually deny any romantic feelings for eachother but will frequently show jealousy when the other person is in a relationship, i.e. when Ziva was with Micheal, Ray etc. or when Tony became involved with E.J. and Jeanne.
- In Suits, Rachel kisses Mike after finding out he has started a relationship with Jenny.
- In Raising the Bar, Bobbi gets jealous when Jerry is attracted to a professor he has brought in as an expert witness. He calls her out, and she finally wisens and acts on her feelings for him after pushing him away a few times.
- In Leverage, Paker shows pretty much no interest in Hardison, in fact most of the time she is rarely focused on anything rather then her next theft. That is until Hardison shows an attraction to a client who is also a hacker, to which she starts to show clear jealousy towards this relationship.
- Played straight and then averted in That '70s Show. Hyde realizes he has feelings for Jackie, who has been pursuing him and trying to make him jealous. They then go on a date and realize there's not actually any chemistry between them. (...Then later they hook up out of boredom and become a couple for a time, until Hyde runs off to Vegas and drunkenly marries a stripper.)
- Caroline has one in the 3rd season premiere of The Vampire Diaries after seeing Tyler with a date during Elena's birthday party. Being what she is, she mind controls the girl to go away and makes her feelings for Tyler pretty clear. Cue Relationship Upgrade.
- Paramore's "Misery Business" is an extended musical Take That to the former girlfriend in this situation. Including calling her a whore. Given that, according to Hayley Williams, it's based on events from her own life, it's a possible twofer...
- Avril Lavigne's "Sk8er Boi" is a song about a girl who is in denial about her love for a boy she knows until he's already been claimed by another. Unusually for arcs invoking the trope, she doesn't get him in the end. Here the rival is the song's point-of-view character, possibly the artist herself—more normally we follow the fate of the girl having the epiphany.
- Toby Keith's "How Do You Like Me Now?" is about a guitarist/songwriter gloating through the radio at the girl who rejected him in high school and went on to marry some rich guy who never has time for his family.
- "Judy's Turn to Cry" by Lesley Gore (the sequel to "It's My Party (And I'll Cry if I Want To)") has the singer get Johnny back this way.
- Tchaikovsky's Eugene Onegin has a tragic example: Eugene hadn't returned Tatyana's affections until after she married Prince Gremin, after which he realized that he had loved her all along. They meet, and it becomes clear that she still loves him as well, but she decides to remain faithful to her husband.
- Super Robot Wars games plays with this trope and Kouji Kabuto. Kouji in Mazinger Z has Love Interest in the form of Sayaka. Kouji also appears in UFO Robo Grendizer, where he has another Love Interest, Maria Grace. Both of them are Tsunderes. It's a Running Gag that whenever they meet in Super Robot Wars game, they both gets hit by a Green-Eyed Epiphany and starts fighting over him. The best part? Kouji has no idea what's going on.
- Valkyria Chronicles plays with this trope when dealing with Welkin and Alicia. Welkin's mannerisms and (for the lack of a better word) obsession with nature put Alicia off in the early going, but as the game progresses, she begins to appreciate how Welkin's knowledge gets them out of rough situations. The anime, however, jacks it up to eleven.
- El Goonish Shive: Sarah isn't in denial, but Elliot is, and he's dating Nanase. When Sarah finds this out, she runs off crying. Who steps up to the plate and fixes things? Nanase, of course, by dumping Elliot so she can move on and he can be with Sarah. It helps that Nanase's a lesbian and realizes later that this is why she never felt sexually attracted to Elliot.
- Margaret from CRFH only starts to return Dave's affections when he finally starts to return Blue's.
- Skin Horse: Marcie has started 'dating' Chick Magnet/Wholesome Crossdresser Tip. Slightly less effeminate Chris (who is begrudgingly forced to admit that he understands why Marcie is attracted to Tip a little too well) won in the end when his jealousy forced him to make a move for Marcie... which may have been Tip's intention all along. For the record, Tip's reaction to being dumped was essentually "K. Can we still have sex?"
- Bittersweet Candy Bowl: LUCY. Oh dear god, Lucy. After nearly a decade of Belligerent Sexual Tension with Nice Guy Mike, she finally realizes she's in love with him - almost a year after he gets back together with Sandy! To add insult to injury Lucy's constant teasing has pushed Mike to the point where he wants nothing to do with her. Can you say "heartbreak?"
- In Shadow of the Templar, Sandra's jealousy of Mike's relationship with Diana is one of the major things that lead to them becoming a couple at the end of the third book.
- Code Lyoko: Tired of this trope rearing its ugly head over and over again between her and Ulrich, Yumi finally decides to put a stop to it by once and for all being Just Friends. The plan has failed as marvelously as you would expect.
- Kim Possible:
- Ron's jealousy over Eric was crucial to helping him discover his own feelings for Kim.
- The convenient Mankey/Monkey concerns Ron had about Kim's earlier boyfriend, Josh... although Ron helped her somewhat with that romantic pursuit despite his misgivings.
- The same happened to Kim herself, when she jelled against Ron and Yori. And Ron's growing friendship with Felix as well, which was especially amusing since Kim apparently has a "Ron Night" each week that both she and her parents are aware of and yet didn't consider that maybe they had a little more going on than simple friendship.
- And by dating we mean constantly making out