So this guy hasn't seen his childhood friend in a long time. Then they meet again, and she's absolutely stunning. He realizes that his friend that he never thought of "that way" really can be thought of "that way," usually as she starts dating someone else. If he gets her in the end, it will invariably be revealed that she had been in love with him all along; she just needed a new hairstyle and contacts for him to finally notice her.
A variant of this: the first story part, they're so-so to okay looking. Cue the sequel, and BAM! knockout. There are various reasons for this; sometimes the character was too young to be thought of "that way" in the first part. In live action shows and movies, this can happen to a character when puberty hits the actor or actress like a colony drop.
This is Truth in Television for many girls in their early teens, though it's not often addressed in TV or movies, where girls are absolutely ecstatic about their physical changes and the (male) attention it gets them. This can happen for a variety of reasons.
Despite the trope's name, it is hardly an always female trope and gender flips are pretty common.
Contrast with Lolicon, and I Was Quite a Looker. This can sometimes lead to First Girl Wins. This sometimes overlaps with She Cleans Up Nicely. Might happen to a Kid Hero All Grown Up.
In-universe examples only, please. Although the audience can definitely feel this way about a character, this only applies if the character's change is acknowledged in some way by another character.
The TV version of Neon Genesis Evangelion implies this trope with Asuka, and actually plays itbackwards, depriving the audience of a straight-forward, introductory glance at her. We have not even seen the "fanservice" portions of her body before both she - now fourteen - and Misato acknowledge that she's "filled out" nicely since their last meeting - when she was closer to eight. It is only later in the series when we see her at a much younger age and how she grew up into the attractive girl she is at fourteen.
Genderswapped in Magic Knight Rayearth. Ascot the Summoner was a little boy in the first part of the series, but when the Knights returned to Cephiro in the second part, he was a handsome teenager tall enough to tower over the girls (even more with his Nice Hat). Caldina says he "grew up" out of love for Umi, but he denies it (though his Luminescent Blush and his behavior towards Umi say otherwise...).
Another genderswapped variation occurs in Kekkaishi: Tokine initially has difficulty seeing Yoshimori as anything but the crybaby kid she used to try and cheer up when they were younger even after other people have pointed out that he won't stay a kid forever. Events later in the manga, however, have her admitting to herself that Yoshimori is growing to be a strong, reliable young man. She even finds herself imagining how he'd look in a few years and finds her mental image of an older Yoshimori "surprisingly cool-looking."
In Fullmetal Alchemist, the main character Edward's love interest/childhood friend/automail mechanic has been out of town with a job for months, and Edward finds her, has his limbs adjusted, and goes on his way. Winry notes to herself (as she further realizes she is in love with Ed) that his back/shoulders are broader now, and Ed is becoming a man and is no longer a child. At least in once instance, this was mostly due to Ed regaining his self-confidence and his posture improving as a result.
This happens to both Goku and Chichi in the last part of the original series (before it became Dragon Ball Z). First, Bulma and company didn't recognize the 18-year-old Goku at first, having gained a couple of feet of growth and the hotness to match (Bulma herself couldn't help but hesitate a little). They could only believe it when he revealed his signature hair. Then, Goku didn't notice that the Tsundere he was fighting against in the Tenkaichi Budokai quarterfinals was the girl he agreed to marry when they were kids (she entered the tournament anonymously), and he didn't find out until Chichi revealed herself. ("But-but-but are you the same little Chichi I met so long ago?!" "Hey, of course I am!") Basically, she got tired of waiting for him and decided to approach him more on his terms...and this time it stuck.
There's also the time that Bulma learned that (future) Trunks was her Kid from the Future. Her reaction (after the requisite GASP! of surprise, of course) was, "My kid's gonna grow up hot? Sweet!" She also has some trouble keeping her thoughts about Goku entirely platonic ever since he turned eighteen — even after he's married.
Subverted in Season 1, everyone was surprised when Sakura returned looking exactly like she did 6 years ago (a little girl). She leaves at the end of Season 1, but on her return halfway through Season 2 (years after the first story) she looks... exactly the same.
In the sequel D.C. II, which takes place 50 years after the original, Sakura still looks the same.
A series of Age-disguising pills causes this to happen with Negi and his students a couple of times, although the girls didn't recognize it was him. Later, a few more girls get a similar effect when they see how his father looked.
This is repeated later in the series (the Magic World arc). This time around, though, some of them are catching onto it.
Also noted by Rakan in referring to Asuna. But since it's Rakan, he says 'Look how big you've gotten!' and pokes her breast. Followed by Asuna decking him and him pretending to fall off of Ostia.
Setsuna: Ojousama really has grown into a beautiful young woman. Why am I so shaken up?
Similarly, the young Yukari Sendo from Rosario To Vampire takes a dose of temporary aging pills in season two. To her relief, she learns that the only thing separating her from the rest of the harem is about four years—she just needs to be patient.
Sasami. The world's most adorable girl is shown several times over the course of the series that she's going to grow up to be drop-dead beautiful — there was even a short story in the manga where Ryoko points this out to Ayeka — "Sure she's a kid now..." She's so far beyond Ryoko and Ayeka's league that the two can't even come up with a decent come-back in the OVA. The best they can come up with is insulting each other and comparing themselves to her. Or at least, that's how the two of them seem to see it.
In one episode of the original series, Ayeka on seeing Sasami's adult form in Tsunami bemoaned the fact that her sister's beauty would soon surpass her own.
Genshiken starts with Saki noticing her old childhood friend, who's grown into an incredible Bishōnen.
Ai Yori Aoshi's Kaoru gets this when he realizes the lovely adult woman he meets at the start of the series is the same little girl he played with as a kid. Not to mention he gets an up-close and personal introduction to just how well she developed during that first night.
England leaves the young America and tells him to grow taller and stronger. When they see each other again... oh, my. America is quite taller than England.
There's also France's reaction to pubescent-but-not-quite-legal-looking-Italy.
Italy: What's intercourse? France: It's something you do with someone you like! ...So, Italy. Do you like me?
Played with when Hungary and Prussia meet as teens after she's defeated by the Ottoman Empire. Only then Prussia fully realised that the kid nation he used to fight against more than once was a very busty and pretty girl instead.
Yuki in No Bra is all grown up to the main character...the catch is that Yuki is male. Later on, so is Kaoru. They were in the same nursery, at least.
According to Tsunade, this happened to Kushina, Naruto's mother.
It also happened to Tsunade herself. Back in her genin days, she was called flat-chested by Jiraiya. The difference between her child and adult physiques was lampshaded in an omake of the anime.
In the first episode of Basquash!, Dan realizes — a little later than Miyuki would've wished — that the busty mecha mechanic he's been hanging around with for the past few hours was his childhood friend from years ago.
There's a variant in XXX Holic, as of Chapter 187, as Kohane visits Watanuki some years after he's taken over Yuuko's shop, and comments on how good she looks in her school uniform. When she responds that he's constantly saying it, his response hints at this trope.
On the female side of things, Nia goes from cutie princess to a real knockout◊ after the time skip. It's not seen much, but Darry seems to grow up pretty nicely, too.
In Maid-Sama!, when Misaki last knew him, Hinata Shintani was a fat gonk. Ten years later, Hinata returns as a wide-eyed Bishōnenwith the personality of a hyperactive puppy and his mind set on finding his first love (Re: Misaki). In a subversion, Misaki doesn't particularly seem to notice or care very much. Her younger sister Suzuna, on the other hand...
In the final episode of Library War, Komaki and a young neighbor that he only ever thought of as the little girl next door, until she turned nineteen or so.
Chapter 45 of Natsume Yuujinchou has a bit where a girl named Miyoko complains to a friend while walking home about how this Creepy Child she knew back in preschool named Takashi Natsume. Miyoko's annoyed because he's going to be in town for a couple of days, and since her parents invited him to stay at their place, she's gonna have to put up with him the whole time. Ugh! But enough about that, why don't they talk about who that really cute guy standing at the front door is and why he's waiting there like...Oh.
In a scene later on in YuYu Hakusho, Yusuke stares at his childhood friend/love interest Keiko's body before remarking, "...since when did YOU start filling out in all the right places?", which promptly results in him getting smacked.
Yuki in Wandering Son was surprised to see how her middle school crush grew up once he reached high school, considering she dropped out of school in middle school and became a Hikikomori.
Tsugumi Shibata from season 1 of Hell Girl reappears in season 3 as an stunning adult, bonus points for becoming a nurse.
The page picture comes from a hentai manga. It contains a common plot in which a guy notices a female friend of his is lookin' mighty fine, and eventually they become a couple. You know what coupling is, right? It's sexual intercourse.
In DN Angel, Rika decides to go check on Daisuke after he mysteriously collapsed in the middle of school. After getting flustered at the sight of his sleeping face, Riku notes that Daisuke looks a bit more mature than she remembers him being, and that it's only a matter of time before he turns into a full-blown bishonen.
In Haruhi Suzumiya, present-Mikuru is a little moe girl who (despite having a large male following) is generally referred to more as cute or adorable than hot or sexy. Her future version however, generally gets labels like "bombshell" applied to her, and whenever she does anything at all, Kyon uses adjectives like "seductively" to describe it. It's hard to tell in the anime because of Generic Cuteness, but future-Mikuru is still drawn a bit more beautiful than her younger version.
In Miyuki, Masato feels this way regarding Miyuki Wakamatsu - who is his stepsister...
In episode 4 of Burn Up Excess, we learn that when Maya (who edges out Rio and Nanvel by 1cm for the bustiest of the squad) left for the Tokyo police academy, she was a Tomboy. When she returns home to Osaka on personal business, everyone was surprised when they learned just how much she filled out while she was in the academy, and there was a Running Gag where she slugged everyone who noted it in a specifically lusty manner.
In Bleach, this happens to Urahara's child assistants Jinta and Ururu after the Time Skip. Jinta became very tall and muscular, while Ururu became taller with larger breasts and attracts male attention. Also happens to Ichigo's sister Karin. Post-Time Skip, not only has she filled out considerably from her Tomboy days, she's also picked up more of her brother's spiritual awareness.
In Kare Kano, Takefumi's appearance has changed so dramatically from when he was a fat, bullied kid that Tsubaki, the girl he liked back then, doesn't even recognize him at first. He takes advantage of this to get close to her with the intent of getting revenge on her for her only pretending to be his friend back then because a teacher ordered her to. Funnily, it later comes out that Tsubaki actually liked his fatness so much that she tries to fatten his slimmer older self back up.
Sin City. John Hartigan saves eleven year-old Nancy Callahan from a pedophile rapist. Eight years later he walks into a bar looking for her, and is dumbfounded when informed she's the buxom stripper (played by Jessica Alba in the movie) up on stage in the cowgirl outfit.
Skinny little Nancy Callahan. She grew up. She filled out.
The comic strip For Better or for Worse had a slight variation: Michael returned home to find that his sister Elizabeth was actually good-looking, and remarked on this, prompting her to go mark that date on the calendar. In another strip, he noticed that she actually looked similar to his girlfriend Deanna. Brain Bleach may have been needed.
In The Fabulous Furry Freak Brothers Fat Freddy goes back to his hometown and meets an attractive teenage girl who invites him home. As they're sharing a bath together, her parents come home - and Freddy realises they're his parents too, having not recognised his now attractive sister.
In the very first issue, Alex refers to Nico as "that dorky girl" who borrowed his DVDs of The Prisoner the previous year and never returned them. When he sees her again, he is literally speechless. A flashback much later on shows that the younger Nico had shorter hair, glasses, and a much more conservative wardrobe.
In the second volume, the gang meets a future version of Gert, described in Brian K. Vaughan's script as "busty" and "very, very attractive." The Gert fans know and love is an overweight, bespectacled nerd.
Layla Miller in X-Factor. She was stranded in the future as a prepubescent girl, and returned as a young woman, with hips and "things" as Jamie observed.
Gender-swapped in Zot: Short-and-nebbish Woody, who has a crush on Jenny (who of course only has eyes for hero Zot), goes to France for the summer. When he returns, he's six inches taller and quite a bit buffer. Jenny's reaction: "My God, he's adorable!!"
A story titled "A Date with Suzy Stringbean!" had Betty set up a date between Reggie and an old classmate who had a crush on him, Susan Starn (or Suzy Stringbean, nicknamed because she was the skinniest girl in the class). Reggie fakes an illness to get out of the date, so Betty sends Archie in his place. When Reggie sees Suzy the next day:
Reggie: S-Sue-Suzy! You've filled out! I mean, you've grown up! I mean, I don't know what I mean! [face turns green] Suzy: Gosh, Reggie! You must still be sick! You're turning a bit green! Betty: Yeah! Green with envy!
Another example: The reason Jughead avoids women is because he fears his heart is going to get broken a second time; the first was when his first love and childhood friend Joani Jump moved out of town. Or maybe he who moved away from her. At any rate, in one story, when they reunited briefly, for the first time since they were about five years old, she was a knockout. Even Reggie was a little flustered when he saw her. (Archie had more respect for Jug to leave them alone, dragging Reggie with him.)
Astérix Legionary has Panacea, who returns after many years studying outside the village.
Later played straight in a minor way with character Toopie, who started out as a regular child and as such was still able to grow up until she reaches 12. When the heroes meet her again, she has reached such age, and Razzia is quick to notice how much she has grown up, pissing his girlfriend Tenebris off in the process.
Supergirl started out being depicted (and drawn) as a typical teenager, with Supergirl rarely looking more than 13 or 14 in most of her early appearances, only by the mid-1960s to be depicted and drawn as a sexy 20-something woman. Although "eye of the reader" does not apply for this trope, Supergirl becoming a woman is touched on in numerous issues, as well as implied by the comics allowing her to establish relationships with characters other than Sparky the Super Cat, Krypto the Super Dog and Comet the Super Horse.
A 1967 issue of The Mighty Thor features the first modern encounter of Thor and Lady Sif. He is surprised because he remembers her as a child who he used to dangle upon his knees, and he now sees her as a stunning beauty. He concludes that: "By my mallet-thou art child no longer!" This was also Thor's reaction to meeting the grown-up Lorelei, Amora's younger sister, who is in the process of using magic to seduce and rape him. The last time Thor saw her she was still a child.
An early-to-mid 60s installment of Peanuts has Linus reading the paper and fretting because...
Linus:Annette Funicello is all grown up!!
In A Pleasant Surprise, both Fluttershy and Midnight have this reaction to each other, given that they haven't met in years. Fluttershy didn't expect him to have grown up to be adorkable, and Midnight had no idea that Fluttershy had gone from cute to amazing.
In the Buffy/Stargate crossover fic All Your Base Are Belong To Her, we catch up with Dawn as she approaches her eighteenth birthday. Although she had been cute enough even as a young teen, Dawn has come along nicely in the two and a half years since the end of Buffy Season Five, and is acknowledged by most (though not all) of the characters she meets as being a legitimately gorgeous young woman (as well as being an insufferablebrat, but that's another point altogether).
In the Harry PotterFan FicAfter the End, everyone is surprised to suddenly find out Eloise Midgen has become extremely attractive. Also Colin Creevey has become rather tall and good looking. There are a few fics out there that sometimes depict Neville has having grown out of his awkward younger phase and becoming something of a stud. No doubt, there is some influence the similar transformation of Matthew Lewis, the actor who plays Neville in the films.
In the How to Train Your Dragon alternative continuity fanfic, Hitchups has a parental version of this when Hiccup, having fled Berk with Toothless for two years of adventures, returns to help his people against the Red Death. To the Berkians amazement, the clumsy boy named Hiccup has returned as a mighty and tested Dragon Rider warrior on top of being a brilliant inventor and dragon expert favored by Thor himself.
In the Kingdom of Heaven fanfic, Prelude to Heaven, Balian is tall, gangly, pale and somewhat clumsy. Then after serving in an army, turns into... well, what Orlando Bloom is. This is noted by the girl he was crushing very badly on, who didn't recognise him and had had a bad experience in the intervening years before he sweeps her off her feet as it were.
Naruto and Hinata in Twice Shy (sequel to Two Halves). Long story short, Tsunade convinced an old student of hers to take Naruto and Hinata for training during the time skip. They come back and well... Hinata has more confidence, doesn't stutter and wears modest clothes that don't hide her figure. Naruto thinks before he talks, eats a balanced diet, is less impulsive and (due to the proper diet and training during time skip) is 6 feet tall and ripped. When they get back to the village Kiba is practically foaming at the mouth at seeing Hinata. Sakura and Ino knock on Naruto's door and look down for when he opens it thinking he's still short... they end up staring at his chest.
In the Fullmetal Alchemist fandom, this is extremely common in Roy/Ed fics, though it's likely to show up pretty much any time one of the Elric brothers or Winry is paired with an older character.
Similar to The Great Mouse Detective example above, a subset of the Wreck-It Ralph fandom will age up Vanellope in order to ship her with Ralph, this trope is justified due to a graphics update to her game as a whole or from someone messing with her code.
In Children of Time, Sherlock Holmes first meets Beth Lestrade when she's a fifteen-year-old, Hot-Blooded tomboy. When he sees her next, she's seventeen and has matured quite a bit in the past couple of years, acting far more like an adult than a kid. He's left unsure of how to handle it.
Played with/subverted in a number of Steve/Bucky fics that portray Bucky as having already fallen in love with Steve before he became considerably taller and buffer (although here, it's not the result of natural growing-up but the result of a super-soldier serum) and consequently needing some time to get used to Steve's new body and/or feeling jealous/insecure about how Steve gets a lot of attention from women now and doesn't need Bucky to look after him anymore. There are a number of AU fics for them too, though, that tend to play this trope straighter.
Film — Animation
Nala in The Lion King. In the sequel, Kiara seems to react more to "he's grown up" than Kovu does to her when the first reunite.
A somewhat wacky version in Brother Bear 2. By the time Kenai meets his childhood friend Nita again, she's a pretty young bride-to-be, and he's a bear. It works out in the end; Nita becomes a bear in order to stay with him.
Just Friends stars Ryan Reynolds as the fat, nerdy teenager in love with his best friend, Amy Smart, who loves him "as a brother". He runs away and 10 years later is rich, cool, and good looking. He comes back into town where she immediately is struck by his new appearance.
The movie The Namesake, based on the book of the same name by Jhumpa Lahiri, has an example of this when Gogol/Nikhil meets Moushumi Mazoomdar again after meeting her in high school. They eventually get married, but Moushumi has an affair with a friend from college.
Gigi. The plot pretty much turns on the fact that the male lead falls in love with the female lead without even knowing it because he considers her a child, and therefore discounts her charm and appeal until it is all-but shoved in his face (so to speak)!
This trope can be inferred in Lord Steyne's attraction to Becky Sharpe when he meets her as an adult after having had an interesting encounter with her as a child in The Film of the Book of Vanity Fair.
In Rush Hour 3, we meet Ambassador Han's daughter again after almost ten years. Carter mentions that they should get her a teddy bear, then he sees her and adds "or a bra!". Surprisingly though, for a film series about as bawdy as PG-13 can get, it doesn't play up her attractiveness very much beyond that.
In She's Out of Control, dowdy Katie gets a makeover where she gets contact lenses, a new hairdo at a professional hair salon, a new wardrobe, and her braces removed while her father is out of town. He returns to be shocked and horrified that Katie is now being chased by practically every teenaged boy.
A male example in Star Wars: Attack of the Clones, when Padme sees Hayden Christensen-era Anakin for the first time. He replies "So have you, grown more beautiful... for a senator, I mean."
Enrique's and Ignacio's reunion as adults after not having seen each other after grade school in Bad Education has shades of this.
Archie: To Riverdale and Back Again (released on video as Archie: Return to Riverdale): This live-action TV-movie is about the high-school reunion of the comic book characters, now adults. Jughead spends most of the movie trying to avoid Big Ethel, but he decides to confront his fears and goes to her house. She's now a supermodel.
During the first The Fast and the Furious movie Mia mentioned this as having happened to her brother Dom in regards to his relationship with his girlfriend Letty.
Mia: Letty grew up just down the street. She was into cars since she was like ten years old. Dom always had her attention. Then she turned sixteen... Brian: And she had Dom's attention. Mia: Yeah, it's funny how that works out.
In most variations of The Phantom of the Opera, Christine and Raoul are childhood friends, becoming involved after Christine's musical enhancement by the Phantom. In the musical version by Andrew Lloyd Webber, Raoul actually sings the line "Can it be? Can it be Christine?/What a change! You're really not a bit the gawkish girl that once you were!" in the song 'Think Of Me'.
Spoken nearly word for word by Joe Keller about Ann Deever in Arthur Miller's All My Sons, though it's his son that's interested in her.
Eddings uses the trope in The Elenium, with Sparhawk not being sure how to deal with the now-adult Ehlana (once she's out of the crystal).
The pre-reviz Magic: The Gathering novel featured the initiate druid Greensleeves, in her late teens, being spirited away by an archdruid for a crash course in advanced magic. Her brother and some trackers took a week or two to find where she managed to get to in a single night. When they arrived he saw she had grown taller, gone from a skinny youth to being, as the cliche goes, a woman with curves in all the right places—perhaps older than her brother (in his early twenties)—and lost her stutter. The implication is that her mentor did a magical version of SORAS, compressing time for her so she could learn what she needed before she needed it, which she wouldn't have if she had been taught the traditional way, over years.
A Song of Ice and Fire has the returning Theon Greyjoy flirting heavily (and we mean heavily; there is groping aplenty by both parties) with a local ship builder's wife while talking about his little sister Asha, who was a skinny little thing with knocky knees and who allegedly has grown into chain mail and leather underclothes. Surprise; the ship builder's wife is Asha, who was deliberately fucking with him. Theon is none too pleased.
One Star Wars EU novel features Wes Janson (who flew back seat with Wedge Antilles at Hoth) flirting with a female pilot, who he later finds out she's Han Solo's daughter.
Invoked in Keith Laumer's Retief's War, when Retief meets a very attractive girl he has no memory of ever seeing before ("Sorry — and I do mean sorry"), although she clearly knows him. Subversion, or maybe not, since she turns out to be his cousin.
"You couldn't be over twenty-one," Retief said. "It would take more than twenty-one years to forget that face." The girl tossed her head, her eyes sparkling. "Perhaps you'll recall the name Fianna Glorian...?" Retief's eyes widened. "You mean little Fifi...?"
"Mithros' spear, Kel, you're a girl!" "I've always been a girl." "But a girl girl! With a chest and everything!"
Molly Carpenter of The Dresden Files. Harry met her first when she was "somewhere between training wheels and training bra" and doesn't realise she's turned into a complete stunner until she calls him to help bail her boyfriend out of jail...
In the first Gotrek & Felix novel, the main characters save a young girl named Kat from a Chaos warlord. When they return to the region a couple decades later in Shaman Slayer, she has become a badass Beastman hunter and quite an attractive young woman.
An interesting variant happens to Cosette in Les Misérables. Fresh out of a convent school, she's a mousy little thing who Marius (her future husband) and Courfeyrac just think of in passing as 'Mademoiselle Lanoire' for her plain black dress. Then she herself notices she's gotten pretty, and makes more of an effort to dress accordingly, turning heads wherever she goes and causing Valjean, her adopted father, a lot of anxiety. Courfeyrac notices the change immediately, but Marius doesn't - until he meets her eyes.
Clara del Valle, the soon-to-be matriarch of the Trueba family, was a kinda ugly little girl at age 12 when Esteban's fiancče and the World's Most Beautiful Woman Rosa died. Some years later Esteban, now a Self-Made Man, asks the Del Valle family for Clara's hand in marriage... and is stunned to see that the 20-year-old Clara has grown into her looks quite a bit.
Esteban and Clara's eldest daughter Blanca was rather ugly when she was born, average-looking as a child, and a total beauty as a teenager/adult.
Blanca's love interest Pedro Tercero was a Country Mouse as a boy, then borderline Tall, Dark and Handsome as a teen/grown man. Then he loses three fingers, but has the charisma and the singing/songwriting skills to be still very attractive in the eyes of the women around him.
In Shimmering Splendor, a retelling of the Eros/Psyche myth, Psyche was very plain-looking when she was young and her family and neighbors grew so used to her plain looks that they didn't realize how much she changed as she grew older until a newcomer to the town tried to abduct her in the middle of the night.
Live Action TV
The Brady Bunch: Season 5's "Peter and the Wolf" has Greg (desperately) trying to get one of his buddies to date his girlfriend Sandra's cousin, Linda (on a double date to the drive-in movie theater). All of them say no. Why? Because when Sandra last saw Linda several years ago, she was a nerdy girl in pigtails and thick horn-rimmed glasses, and wearing braces. Greg then talks Peter into posing as one of his buddies ... and then needless to say, on date night, Linda had grown up -- hotter and sexier than ever!
In Boy Meets World Cory and Shawn are stunned when they find out Topanga went through puberty during summer vacation.
Shawn: "That's a nice blouse." (stares at Topanga's chest)
Topanga: "Thanks, I got it over the summer."
Shawn: "Summer was very good to you."
Topanga: "At least what I grew is real." (Rips Shawn's fake sideburns off)
It happens with Kevin's cousin in an episode starring Soleil Moon Frye.
Reappears in the sitcom Working, when the two Wonder Years actors meet in this setting.
Parodied in The Monkees episode "The Monkees in Texas". Mike visits his aunt in the Lone Star State and meets his cousin Lucy, whom he has not seen in years and of course is now gorgeous. He marvels over how the knock-kneed girl with bad teeth he used to hang around with is now a beautiful swan, until his aunt informs him that he is confusing Lucy with his other cousin, Clara, who still looks the same.
Gender flipped in Sister Sister. Tia and Tamera's neighbor Roger was always trying to get a date/a kiss/SOMETHING from either one of them and they'd always blow him off with "Go home, Roger!" Over one summer, however, he goes through puberty, turns into a hunk ("from AS IF...to ALL THAT!"), and the girls spend an episode fighting over him before realizing they'd still rather just be friends with him.
Twisted in an episode of Two and a Half Men, where a homely childhood friend of Alan's shows up, now a knockout. As Alan and Charlie compete for her affections, she reveals she had starved herself and had plastic surgeries to make herself beautiful, so she could rub it in their faces for teasing and ignoring her in high school.
The second episode of Blossom is called..."Blossom Blossoms". Three guesses as to what it's about.
Towards The Republic: When Sun Yat-sen first met little Song Qingling, she was a seven-year-old girl. And when he met her again years later, she had grown into a nubile young woman whose childhood crush on him had become full-fledged love.
In the first episode of The Steve Harvey Show, Steve realizes that Regina Grier, the fat girl he tormented in high school is no longer fat, and is now his boss at the high school he teaches at.
Another episode featured an incredibly sexy babysitter hired for the boys, who turned out to have been an old classmate's of Francis'. Francis calls them from military school, and we see his image of her as an obese, awkward nerd.
Mike, on the first day of school, spots an incredibly beautiful girl in the halls and spends the day following her around trying to get her to tell him her name. She seems to know him already. Turns out that she's "Buck-Toothed Becky," whom he used to mock for getting corn stuck in her braces.
Mike's friend Boner catches Carol in her night gown, ogles her chest, then says to her "Well, they're growing quite nicely."
Amy Pond in the episode "The Eleventh Hour". The Doctor meets her first when she's seven, and after accidentally time travelling 12 years doesn't recognize the older Amy at first since she's understandably grown since five minutes ago.
The cricket bat to the head may not have helped.
"The Girl in the Fireplace" features a similar time jump with the Doctor first encountering Madame de Pompadour at the age of 7. When he meets her again — a few minutes later by his reckoning — she is played by the gorgeous Sophia Myles.
In the episode "Making the Girl", Castle runs into a model who knows him from somewhere, but who he doesn't remember. She gives him her phone number anyways, much to Beckett's chagrin. His teenage daughter informs him that the model in question is in fact the gangly girl who used to babysit her years before, making Castle feel like a Dirty Old Man.
Castle has this reaction to his own daughter while at a sci-fi convention. After cooing to Beckett about how cute Alexis was dressed as a little Princess Leia, he later freaks out when she walks by (under)dressed in a stripperiffic cosplay outfit.
Inverted on Friends when Monica is all grown down between her first and second meeting with Chandler. There's only a year gap but she loses a ton of weight and he's totally gobsmacked.
On Maury, he will often feature people who used be nerdy or obese (or both) who improved their looks (usually with plastic surgery). The girls are often Stripperiffic and the guys are usually muscle-bound beefcakes.
After listing off the varying ways in which America isn't doing to well at the moment, Stephen Colbert consoles the crowd at the Clinton Global Initiative by pointing to Matthew Lewis's successful conquering of puberty.
Colbert: And, most importantly, Neville Longbottom now looks like this. I think we can all agree that that is a real message of hope.
On a recent episode of Glee, Kurt is seen looking significantly buffer and flexing muscles previously not seen in his stage combat class at college, joking with his friends that he's "finally hit puberty." Several people, girls and guys alike, look on appreciatively while Blaine, his fiancé, jealously eats Cheetosin the background.
On an episode of Welcome Back, Kotter, Juan Epstein's slightly younger sister puts in an appearance. Barbarino remembers her—but not quite like that.
Barbarino: So, Carmen... you've filled out!
Subject of the songs "Happy Birthday Sweet Sixteen" and "Next Door To an Angel" by Neil Sedaka.
"She Hasn't Always Been This Way" by Doc Walker combines this trope with Unrequited Love Switcheroo, as the singer realises that his friend's sister (who used to have a crush on him) has now grown up into a very attractive young lady who won't give him the time of day.
"She hasn't always been this way. I really can't believe how much that girl has changed. She's out of my life, she's out of my reach, I'm out of her mind, she's out of my league..."
An angle in ECW between Tommy Dreamer and Raven revolved around a fat girl named Beulah McGillicutty whom Dreamer and Raven had both known at summer camp. Dreamer had made fun of her at the time for her weight, see, and so she fell in with Raven. Beulah grew up not just to be a hottie, but according to many wrestling fans, the most classically beautiful valet of all time. She ended up with Dreamer in both the storyline and real life.
In a more sentimental and nostalgic way, in Fiddler on the Roof. In the song "Sunrise, Sunset", the older characters come to terms with a young couple getting married. "Is this the little girl I carried, is that the little boy at play? I don't remember growing older, when did they?"
Played with in The Yeomen of the Guard. To avoid execution, Col. Fairfax masquerades as Leonard Meryll, who's been away in the army for years. When Leonard's sister Phśbe greets him in front of everybody, Fairfax is baffled and has to be told who she is. He quickly covers with "Why, how you've grown! I did not recognize you!"
The comedy Two and Two Make Sex spends the entire second act establishing this fact then sitting back and watching the consequences. George discovers that Jane, who he's been having an affair with, is in fact Janey, a girl he hasn't seen since she was three. He was reminded of this fact by his old football friend, Jack, who just happens to be Janey's father.
Barbie has not one, but two kinds of dolls with "growing up" mechanisms that give them taller statures and larger breasts.
8 year old Kaylie from Hunter The Reckoning returns in Hunter: The Reckoning: Redeemer as an 18 year old hottie.
Averted Trope - What Red is to Asellus in Sa Ga Frontier. Asellus used to babysit him when he was a kid, it helps that she hasn't aged a day because of the whole being a half-Mystic issue. But there is no relationship between Red and Asellus other than her watching him when he was younger
Male example: In The Legend of Zelda: Ocarina of Time, Nabooru, upon meeting up again with Link after seven years, expresses much annoyance over the fact that she never gets the chance to give him that "Something Special" now that he's a smokin' Bishōnen.
An example that was a good 4 years (IRL) in the making - in Guild Wars pre-searing there was, once upon a time, a cute little girl named Gwen. She wanted to find her missing flute, and occasionally cast healing spells on you if you had her follow you. After the events of the Searing, the entire countryside was destroyed, and many people died. We never got to find out what happened to her, except we found her broken flute...Three expansion packs and 4 Years later, we got Guild Wars: Eye of the North (GW:EN) expansion. Guess who came back as a fully grown-up woman! (plus full backstory). The player eventually gets to attend her wedding (no, not to the player, to another NPC)
In Fire Emblem: The Sacred Stones, Kyle and Syrene's C support has them realize that they met as teenagers (Syrene was a Pegasus Knight in training for Frelia, Kyle was a squire for the Renais military, some years ago he ran some errands for his country in her land and she helped him with that). Cue Kyle being surprised to see that the cute girl he befriended years ago is now a beautiful Lady of War.
Sera is amazed how much older Hope is in Final Fantasy XIII-2. Justified, since she travelled 10 years into the future and sees the young teenager "suddenly" aged by a decade into a young man. A Live Trigger option during the game can also be used to lampshade her reaction.
In Fate/stay night, Shirou mentions early on that lately he's been getting this feeling for Sakura.
There's a weird "instant" version that happens in the Phoenix Wright: Ace Attorney games with Nick's spirit medium sidekicks Maya and Pearl. In The Verse, whenever somebody channels a spirit, they take on the physical appearance of said spirit. Naturally, when Nick's very busty Spirit Advisor Mia gets summoned by either her teenage sister or her 8-year-old cousin, the... er, maturity is very noticeable. In Trials and Tribulations, the third game, an old man who goes to a coffee shop to ogle the waitresses refuses to talk to Phoenix, who then semi-concocts a scheme to get Maya employed at the coffee shop. He then convinces her to come with him to meet the old man, who looks at her uniform with obvious lechery...until deciding that she's too "small". Cue the spirit possession, and the much more "developed" Mia begins questioning the old man, who is only too happy to provide answers. Lampshaded afterwards when Mia states she "can't believe Maya called [her] for this!" before dispossessing her sister. It's played straight in Dual Destinies, in which we see Pearl again after nearly 8 years, though she still looks just as adorable.
One of the most interesting bits of Tokimeki Memorial 2. The game features an interactive prologue where the protagonist is in grade school, and meets the various female characters as children. After the prologue, the protagonist moves out of town, and is only reunited with his childhood friends when he starts high school (the game proper): naturally, they're all grown up. The protagonist and Hikari, his closest childhood friend, regularly have discussions of how much and in which way they have changed, throughout the storyline. Also, if the protagonist is a Track & Field Club member, and sees Hikari if he peeks at the girls' bathroom during Summer Training Camp, he'll make a comment on how much she has grown physically.
"Uncle" Kunihiko in My Forged Wedding does not have an immediate reaction to seeing the protagonist again once she arrives in Tokyo from Kyushu after graduation from university. Instead, he continues to think of her as the little girl he used to babysit, and only begins to become aware of her as a woman halfway through his route, with a sudden corresponding change in the way he treats her once the realization hits him.
Played with in If My Heart Had Wings: Aoi did already confess to Childhood Friend Ageha before he left, but he'd merely innocently mistaken his worries about leaving for love and didn't really have a crush on her yet. And in process of confessing, he inadvertently offended Ageha by claiming that he wants to go out with her because she's One of the Boys, meaning that in the meantime until they meet again Ageha deliberately tried to invoke this trope by making herself into a cute girl in the hopes that he'd be shocked and humbled when he returns. He's definitely surprised to see his young, boyish friend having turned into a such a pretty girl... but he doesn't remember the comment, and as soon as they start interacting again they fall into familiar patterns. It's not until they get caught in the rain one day and see each other half-naked and wet that it hits the both of them that they're the opposite gender and damn attractive, too.
In Super Dangan Ronpa 2, Saionji is a classical dancer who looks like a child despite being the same age as the rest of the cast. However, the only reason she looks like that is that the cast is trapped in a simulation and look the same as they did when they first entered Hope's Peak academy. Later on, the main character, Hinata, finds a newspaper clipping from the real world that shows how Saionji really looks, and she's definitely grown up, looking taller and much more mature.
Parodied on Homestar Runner in episode 4 of Teen Girl Squad. So-and-So's "imaginary" boyfriend apparently compliments her on how nicely as she has filled out over the summer. She says the same about him.
Scary Go Round did a particularly obnoxious round of this trope in early 2008 - after a three-year absence, the hero's former student-exchange partner becomes worthy of his romantic attentions after straightening her hair and getting contact lenses. She has also become magically cool, interesting and something of a Manic Pixie Dream Girl, the latter probably due to the fact that she is French. Meanwhile the audience is encouraged to laugh at her little sister, who is as ugly now as she was three years ago. But hey, if it follows, said sister will probably grow out of it too.
Dream Tales comics, "A Tale of Two Sisters," "The Big Splash" and "Regression to the Mean" feature a younger sister outgrowing her older sister.
In Kubera, Leez is a gonk (though she's usually drawn with Generic Cuteness in deference to her status as a main character) who gets scowls all the time. Flashforwards and a temporary Plot-Relevant Age-Up show that in a few short years she will be a curvy Statuesque Stunner who turns heads everywhere she goes. And she'll die shortly after. The Plot-Relevant Age-Up was a warning: It was showing her guardian what she would look like twelve hours before her death.
Dragon Ball Multiverse: One of the early fights features a version of Dende's little brother, Cargo, who by this point in time is an adult.
Nella:"Holy shit, Matilda, you've got a great rack!"
Happens in the Kim Possible movie A Sitch in Time, to both Kim's little brothers and Wade.
Happens to Princess Odette in the animated version of The Swan Princess. With the added twist that she and Prince Derek were engaged from an early age, but couldn't stand each other because she was an incorrigible tomboy and he thought girls had cooties. It then gets deconstructed as Derek wants to marry her straight away. Odette then asks him if her beauty is all that matters to him, to which he replies "what else is there?" so Odette calls off the marriage. Derek essentially has to spend the rest of the film proving that his love for Odette is based on more than just noticing how she filled out.
Parodied with Stewie and his old dancing school rival Olivia in Family Guy. Stewie falls in love with her because "she's all grown up," but she looks just the same as before.
On Phineas and Ferb Baljeet has this reaction when his old childhood friend Mishti comes to visit; he refers to her transformation as "turning into a girl" (given the flashback of them playing soccer in the mud, she seems to have been something of a tomboy). Somewhat like the Family Guy example, because both Baljeet and Mishti seem to be preteens who last saw each other as children.
In the five-part story that begins Chip 'n Dale Rescue Rangers, Monterey Jack had known Gadget when she was younger; when he and his two friends first meet her in the story, he exclaims that he hasn't seen her "since you were knee-high to a knee!" (Slightly inverted because Jack shows more a paternal attitude towards her than anything else, since he was friends with her dad and she probably thinks of him as a favorite "uncle".)
Kessie the blue bird Rabbit adopted in The New Adventures of Winnie the Pooh. He raised her until she's ready to fly south. She returns in her next appearance and she's all grown up. Rabbit unable to admit she's grown and Kessie calls him "Rabbit" instead of "Rabbie" like before.
Portrayed in South Park episode "Bebe's Boobs Destroy Society", where the male fourth-graders behaved like apes when they saw Bebe's naturally-developing chest.