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, which almost universally portray girls as absolutely ecstatic about their physical changes and the (male) attention it gets them. Apparently in fiction, a girl isn't allowed to want to be anything but sexy once they hit their teens, but then again there's a reason for that.Unfortunately.
In-universe examples only, please. Although the audience can definitely feel this way about a character, this trope only applies if the character's change is acknowledged in some way by another character.
Contrast with Lolicon, and I Was Quite a Looker. This can sometimes lead to First Girl Wins. Sometimes overlaps with She Cleans Up Nicely.
A more platonic and gender-swapped variant of this trope is seen in the first episode in the original Japanese dub of Digimon Adventure 02, with old friends Hikari and Takeru. Upon their reunion (after a couple of years of not having seen each other) Hikari compliments Takeru by saying that "You've gotten taller." Of course, easily-jealous Daisuke—and Takeru/Hikari fans—had a less platonic interpretation of this observation.
On a somewhat related note, the lyrics at the beginning of the show's first end theme in the original Japanese dub has a line which basically translates to "look at how much I've grown." Obviously, in reference to the original Chosen Children from the first series.
There's a reason the Saban dub places the elder 6 in high school. Hello, Sora/Mimi
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."
Yet another gender-swapped variation occurs 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 Goku and Chichi in the last part of Dragon Ball before the part commonly referred to as Dragon Ball Z. Kind of. Goku didn't notice that the Tsundere he was fighting against in the Tenkaichi Budokai was the girl he agreed to marry when they were kids (and to be fair, the others didn't either; only Oolong recognized her, but he didn't say anything), 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!")
And shortly before that, Bulma and company's reaction to seeing the roughly 3 foot taller 18 year old Goku after he gained a couple of feet of growth and the hotness to match.
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 D.C. ~Da Capo~ - 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 in Mahou Sensei Negima!, 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.
Sasami from Tenchi Muyo!. 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.
In Axis Powers Hetalia, 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.
And then there's 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.
Now 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 pysiques was lampshaded in an omake of the anime.
Was probably the same jutsu, that she now uses to fake youth, that gave her that monster cleavage.
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.
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.
In the Eureka Seven movie, Renton commented to Eureka in the sickbay that she has grown pretty since he last saw her 8 years ago.
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, Yuusuke 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's nothing special, really: one very common "plot" of hentai is that a guy notices a female friend of his is lookin' mighty fine, and somehow, somewhere, for some reason, they couple. You know what coupling is, right? It's sexual intercourse.
In D.N.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...
Setsuna: Ojousama really has grown into a beautiful young woman. Why am I so shaken up?
Sin City's "Skinny little Nancy Callahan". She grew up. She filled out. The older Callahan is played by Jessica Alba in the movie version and is seen on a stripper pole.
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. (Of course, being her brother, he still can't think of her that way for himself...)
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 the recent X-Factor series. 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!!"
An Archie Comics 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!
Astérix Legionary has Panacea, who returns after many years studying outside the village.
the same comic later plays it 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.
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 diea 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.
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.
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.
Kheldar "Silk" of Drasnia, and the Magravine Liselle ("Velvet") from The Belgariad are a pretty good example of this trope.
Eddings uses the trope again 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 Dragonlance Chronicles, Tanis notices this after he pulls Laurana down on top of him. Especially justified as he is a half-elf and she is a full elf, so he hit puberty at least a decade before she did.
In the first Gotrek And 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.
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 sweater. (stares at Topanga's chest)
Topanga: Thanks, I got it over the summer.
Shawn: Summer was very good to you.
Likewise, The Wonder Years with Winnie Cooper. This trope was pretty much a major plot point.
Done again with Kevin's cousin in an episode starring Soleil Moon Frye.
Reappears in WORKING!!, when the two Wonder Years characters 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.
An episode of Cheers has Sam reuniting with an "old" flame and her daughter, who was a child when he knew them before, but now not so much. He tries to sleep with both mother and daughter.
Done on an episode of Growing Pains. 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 Doctor Who 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 Buffy the Vampire Slayer episode "Him", Xander and Willow come to the simultaneous realization that the girl they've both been ogling is Buffy's kid sister Dawn.
The Mayor gets all teary-eyed seeing Faith go on a torture/kill date with Angelus. "She's not a little girl any more."
In the Castle 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.
A mild version on Friends between Monica and Chandler, though only a year passes between their first and second meeting. It's more "she's lost a ton of weight" than "she's all grown up". But his reaction certainly fits.
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.
Subject of the song "Happy Birthday Sweet Sixteen" 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 McGillicuddy 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.
The film musical, and later stage musical, Gigi is built on this trope. Whether it's creepy or not depends on how it's handled; in the original, Gigi is fifteen and her erstwhile suitor is in his fifties, and has had Gigi raised to be his eventual mistress.
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 Phœbe 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
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.
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.
You also have the same thing with Zelda, Ruto, and Malon. Especially Ruto.
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 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.
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.
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.
"Look at you. Why, you're just as pretty as... a magnolia in May."
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.)
Though 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.
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.