Oh no! Somehow your sex has changed! Just when you were working up the nerve to confess your love to that classmate you like! But wait, this situation isn't hopeless...
Now you're the same sex (this trope only seems to happen to heterosexual people) as them. If you become their best friend, maybe you can learn enough about them to date them as your true self, and they'll never figure out that you are the same person! Of course like all the best plans it can and will go awry.
May occur with either Gender Bender or crossdressing (Disguised in Drag or Sweet Polly Oliver) scenarios. Compare and contrast Jumping the Gender Barrier and Unsettling Gender Reveal. Like most Gender Bender tropes this is generally subject to the First Law of Gender-Bending, but there are exceptions.
- Futabakun Change. Although in the end, Misaki finds out, accepts it, and finds a way to Gender Bender herself in the same way to make herself a compatible mate to Futaba-kun/chan, similar to the Zerophilia example below.
- Gacha Gacha: The Secret arc centers around the hero turning into a girl whenever he sneezes and forming a close relationship with the girl he likes.
- CUTE×GUY. One of the few cases of a girl-turned-guy becoming friends with her male crush.
- Pretty Face. Except here only the person's face is changed, not his entire gender, and his love interest mistakes him for her twin sister. But otherwise it fits.
- Kämpfer spends a lot more time having fun with this than it does with the ostensible premise of the show.
- Kashimashi: Girl Meets Girl: Hazumu finally makes friends with his unrequited crush Yasuna after aliens accidentally kill him and revive him as a girl. Unusual in that Yasuna is fully aware of Hazumu's identity and history, she just couldn't get past her own androphobia to make friends with her when she was a boy.
- Fudanshism runs off of this; the protagonist disguises himself as a girl when his sister is too sick to go to a convention where he runs into his crush. To the protagonist's increasing bafflement his crush quickly becomes good friends with his female alter-ego while continuing to ignore the real him.
- Inverted in Ranma ½. Shampoo loves Ranma when he's a boy, because he beat her in a fight and she comes from an obscure Chinese Amazon-like tribe that marries men who beat them. When he's a girl, Shampoo wants to tear him to shreds, because he beat her as a girl too and that's another tribal custom.
- Once she found out that they were the same people and that he was originally a boy, she is just plain affectionate to him/her in both forms, unless s/he pisses her off.
- Played straight with Akane befriending him before she found out that it was actually a boy who beat her in a spar.
- In Kanaete Aizen (Grant My Wish, Aizen) what appears to be a "shy boy wishes for a hot girl and wakes up as one instead" Be Careful What You Wish For plot actually turns out to be a Gender-Bender Friendship plan on the part of a (seemingly) Literal Genie to get Aizen to confess his love for his Unlucky but soon to be Victorious Childhood Friend Yuzu.
- In Ame Nochi Hare, Hazuki and his friends turn into girls whenever it rains. He gets gets more friendly with love interest Asumi as a girl than as a guy.
- Oddly enough, the trope is also played with here. Hazuki, in "Tsukiko" identity, manages to strike up a friendship with Asumi's brother, Takuma. They get along quite well and seem to enjoy each other's company. In guy-form, Hazuki finds Takuma's stoic demeanor to everyone else unsettling and Takuma only knows Hazuki as "Tsukiko's cousin". Hazuki explicitly notes that they wouldn't ever be friends if it weren't for his gender swapping. Asumi and Hazuki's friend Touma ship them.
- Inverted in Nozomu Nozomi: Nozomu concludes the physical genderbender he's been hiding for nearly a year has also become a mental genderbender because his feelings for his unrequited crush Yuka and best friend Yasu have swapped targets.
- Boku No Shotaiken, perhaps the Ur-example of Gender Bender Manga, uses this as the whole basis of the plot: the protagonist has his brain transplanted into the body of a young woman after a partially successful suicide attempt. He then goes back to school seeking vengeance on the girls who drove him to jump off a cliff only to strike up a Gender-Bender Friendship with his old crush instead.
- Inverted in Kanojo Ni Naru Hi Another: isolated loner Rinichi Sagara's hidden Metamorphosis into a female allows him to develop a friendship with male classmate Narumi who learned about Sagara's Gender Bender by accident and decides to help him hide it from the rest of their schoolmates. Played straighter with Kurokawa, who had a mutual Because You Were Nice to Me relationship with Sagara going back to elementary school: Sagara's genderbender allowed their mutual sympathy to blossom into real friendship while his relationship with Narumi eventually blossoms into something deeper. Opening up to Kurokawa and Narumi eventually convinces Sagara the risks of opening up to others are worth the rewards.
- One of the major plots of the Thor fanfic (All) Father Loki. After Loki’s girlfriend, Sigyn, discovers that he had impregnated Angrboda, he transforms into a woman to eliminate the risk in future relationships. It’s Loki’s daughter, Hel, who suggests that he spend some time with Sigyn in his female form to patch up their broken relationship.
- One of the plots in Tootsie.
- Zerophilia is about a genetic condition that switches people's genders after sex, in the end the hero/heroine discovers his girlfriend/friend and boyfriend/rival are the same person.
- In White Chicks, Marcus and Kevin start hanging out with the Wilson sisters' best friends while disguised as them. And when the truth came out, the girls found that they liked the Wilson twins a lot better when Marcus and Kevin were them.
- In Sorority Boys, the three male leads are kicked out of their fraternity and dress up as women to seek refuge in what is deemed the "ugly" sorority house. In the process, one of the men ends up being friends with a girl he'd met earlier and hit on unsuccessfully, but now has a chance to get to truly know. Of course, Hilarity Ensues.
- Some Like It Hot: Two male musicians on the run are forced to to hide in an all-girls band. As girls. Naturally, they become quite chummy with the other musicians.
- The last book in Sean McMullan's Greatwinter Trilogy has this happen to its lovable letch John Glasken. Irony of ironies, he winds up enjoying girl-friendship more than hawt sechs, as shown in the page quote.
- An intensely awkward example happens in Sergey Lukyanenko's Night Watch when Anton's had his mind swapped with Olga. He can't tell Svetlana what's happened until they reach her warded apartment... after she's had a very private conversation with "Olga" about Anton.
- This happened in The Zack Files once, except that the Gender Bent character was trying to set the girl up with his friend, not with himself.
- In the 2004-2005 French series Vice Versa, the main character Thomas sometimes uses his double Emmanuelle/Julia in order to get information on his crush.
- Sabrina the Teenage Witch did this deliberately with a spell to turn her into a boy so she could find out what her boyfriend talked about with his friends when girls weren't around.
- On Charmed Prue accidentally turns herself into a man while casting a spell to find the Femme Fatale Monster of the Week. She's far from happy, but also gets a chance to talk to her current Love Interest and find out what he thinks of her.
- The Order of the Stick has a What Could Have Been example: originally, Roy was going to use the Belt of Masculinity/Femininity to have some "girl talk" with Miko. Burlew decided against this when he realized Miko wasn't quite fit for "lighthearted romantic comedy" situations, so instead, Roy realized his physical attraction to Miko had been a: making him treat like her a sex object instead of a fellow warrior, and b: preventing him from realizing how utterly unlikable she is.
- Misfile is built around this trope.
- In El Goonish Shive, Susan starts out with a low opinion of Elliot. During the time Elliot is stuck as a girl, Susan inadvertently strikes up a friendship with him and he tries to convince her he is not that bad. By the time she sees Elliot male again, he manages to validate the claims he made when he was female through his defense of Ellen which makes her see him in a new light and they eventually become good friends.
- The Fairly OddParents!: In the episode, "The Boy Who Would Be Queen," Timmy attempts to try and find out what Trixie likes and a joke is made on being turn into a girl. Wanda, not finding it funny, turns him into a girl, allowing him to have girl (and boy) thoughts. After getting some payback on his godparents, he goes to the mall and befriends Trixie (while discovering she likes boy stuff, includng dead frogs, which ironically Timmy finds gross). After becoming best friends with her under his assumed gender and learning what she wants, he turns back into a boy, goes to the party and attempts to act sensitive. He's promptly thrown out by security. It should be noted that although Trixie had him thrown out, it looked as though she was genuinely touched by his attempt. She even remembered his name. Since he was only thrown out so she could maintain her reputation, one wonders how she would have responded if they had been alone... wait, nevermind.
- Cybersix has a combination of this with the main character's Secret Identity male persona Adrian with her best friend/love interest Lucas.
- King of the Hill has a variant when Peggy befriends a woman named Caroline, who's actually a crossdresser who mistakenly thinks Peggy is one as well.
- On Futurama Leela pulls a Sweet Polly Oliver to join the military with Fry and Bender. During a talk with Fry she finds out he has a crush on one of his female co-workers.
"Lee Lemons": What type is she? You know, blonde, or Chinese, or Cyclops?Fry: Cyclops."Lee Lemons": (happily) Aww.