Charlie Brown: I think our teacher is in love. Linus: I was afraid of that. I've always hoped that she'd wait until I grew up, and then marry me. Charlie Brown:How would you support her? Linus: We could live off her retirement pay.
Children having "crushes" on one another isn't uncommon. To most children, loving someone just means liking them a lot—they have no notions of romantic or sexual love, and are, for the most part, innocent. They may make a Childhood Marriage Promise with their best friend just because, and even pretend to get "married." Older kids generally have a basic idea of the birds and the bees, but still have to deal with raging hormones and lots of confusion.
What happens when kids get crushes on adults?In some cases, Squick happens. But in most instances, you have an ordinary kid who has to deal with the ordinary awkwardness of having a crush on someone way out of their league.
The Precocious Crush is any instance of a child (usually pre-teen or younger, though young teenagers are sometimes susceptible) having a crush on an adult. Teachers are common targets, as are other, non-related caretakers. While having this kind of crush is more often associated with girls, it is increasingly common to portray boys as having this kind of crush. Usually, nothing ever comes of it—at least not until the character in question is much older, and even then, it still might seem a bit Squicky to some. In animation, the trope can be invoked without fully using it in the case of teenagers, where one character is only a few years younger than their crush, but differing rates of physical development makes the crush look a lot older than them.
Although it may seem to have Unfortunate Implications, this trope is Truth in Television. Lots of kids get crushes on their teachers, after all. See also Puppy Love, where two little kids crush on each other, and Father, I Want to Marry My Brother, which relies on an innocent inability to distinguish between different types of love.
Should anything actually happen in the relationship, see Wife Husbandry, Jail Bait Wait, Hot for Student, and May-December Romance. See also Likes Older Women and Kidanova.
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Anime and Manga
Sasami from Tenchi Muyo! has occasionally expressed some interest in Tenchi (But who hasn't?). Subverted by the fact she's over 700 years old... And then sorta played straight in that, by Juraian standards, she's still considered a little girl.
Played straight with Ryo-Ohki, who is shown to dream of being with Tenchi, where they are picking carrots together. Technically she's a child, but she's also a centuries-old living warship that was reborn after its destruction.
Cardcaptor Sakura: Sakura Kinomoto was like this with her brother's Love Interest Yukito (it was a CLAMP production, in case you were unaware), though they gave it a plot-related propping up towards the end and the two of them ultimately end up with other people (Sakura falls for Syaoran; Yukito, for her brotherTouya. Both of them are around their love interests' same ages). Then there's Rika Sasaki's huge crush on her adult teacher, Yoshiyuki Terada, which is a point of contention with fans since in the manga he apparently accepts and reciprocates it (though he tells her to wait until she's of age).
Happens to Miroku (of course) and a young girl named Koharu in InuYasha, although we only see the second half of it.
By the same author, Ranma ½ begins with Akane Tendo having a one-sided crush on Dr. Tofu, a chiropractor who has apparently been something of the family physician for many years, having been responsible for treating Akane's sprains and bruises since she was a little girl. He is completely oblivious to her feelings for her, though, and this coupled with his freakish obsession with her elder sister Kasumi helps her to get over it.
And then there was Jill (during the Fairy Arc), who looks to be around Schierke's age, and was likewise crushing furiously on Guts. To the point where she persistently followed him around, trying to get him to agree to allow her to stay by his side. In fact, he was pretty much her main reason for not agreeing to become one ofRoshinu'sfaeries when given the chance - her hesitation was shown to be mainly because of her crush on him.
Likewise, in the Hawks camp, young Sonia is head over heels for Griffith.
In the Sailor Moon anime Usagi's brother Shingo develops a crush on Ami. This really isn't all that unreasonable given that the age difference between them is just about four years (Shingo's around eleven, Ami is fifteen) exactly the same for his older sister and Mamoru, in fact the Ami/Shingo pairing isn't even all that uncommon in fan fiction. It helps that Shingo is often presented as more mature than his sister.
Chibiusa has a precocious crush on Mamoru, despite knowing that he's her future father.
She also thinks Shingo (who, for the record, is her uncle) is pretty cute.
Yes! Pretty Cure 5: Nozomi (14) and Komachi (15) have a crush on Coco and Natts, respectively, who are both adults. Fortunately, these guys have feelings for them, too. Bizarrely enough, Coco and Natts are fairy mascots (and princes) who can transform into humans.
Rin (14) has a few crushes on older guys. In the sequel, she and Karen (15) had both a crush on the villain Mucardia who used his human form as a disguise.
HeartCatch Pretty Cure!: A young boy named Hayato is revealed to have a crush on Yuri (17), and Tsubomi, Erika and Itsuki set out to help him reveal it. He's temporarily shot down (and turned into a Desertian) when Yuri says she considers him like a little brother, but when he recovers and she learns how he feels, he realizes he should start small and decides he'd be there to protect her which he does - he's one of the few survivors when the world becomes a desert and is there to help the Precures out of their Darkest Hour.
Tsubomi herself had a crush on the "handsome young man" who is later revealed to be her grandmother's fairy mascot Coupe who transformed into Tsubomi's grandfather.
Doki Doki Pretty Cure: Raquel (around 10) has a crush on his Cure partner Rikka (14). He can transform into a human now, unfortunately, only into a child instead into someone in Rikka's age.
Pinoko, from Black Jack. Not only does she know things someone her age shouldn't, she's really the only person who can assist Black Jack in surgery, gets jealous when he pays any attention at all to other women (well, women, at least), and tends to get around just fine in areas Black Jack doesn't want her around.
This is played with, because Pinoko is actually 18 years old at least. She was originally a sentient tumor (and possible parasitic twin) in the body of a teenage girl, and Black Jack extracted her from her sister's body and gave her an artificial bod of her own, shaped as a little girl. She went to live with him after her "twin sister" freaked out and rejected her,
Poor, poor Masato (Max) from Pokémon (who is not old enough to be a Pokemon trainer) developed such a crush on the youngest Kachinuki (Winstrate). She is more naive than he and ends up breaking his heart.
Kaguya Sumeragi from Code Geass is 14 when she proclaims herself Zero's future wife and proceeds to become the show's Token Mini-Moe. She even proposes the polyamory when someone else tries to tease her about the other women in Zero's life.
It's worth noting that Lelouch himself is 16/17 years (although everyone assumes the masked vigilante Zero is much older under the mask)), so the age difference is quite small, and both are Wise Beyond Their Years, though Kaguya prefers to act younger than she is, most of the time. Nothing becomes of it, regardless.
She's promised to Zero, not Lelouch, so the only thing Lelouch's death and Suzaku taking the name does is add Kissing Cousins to the mix.
Early in Maison Ikkoku, Kentaro Ichinose (the little boy) announces that when he grows up he's going to marry Kyoko, so Godai better back off. Kyoko is amused by it. Later he falls even harder for Kyoko's niece Ikuko, so it wasn't an issue for long. Ibuki gets a big crush on Godai; she's seven years younger but at least she's in high school.
In Skuld's special episode at the end of Ah! My Goddess, she begins exhibiting this trope towards Keichi, but Urd tried to sabotage it and deliberately create a Snap Back- commenting to herself that it was for Skuld's own good. As it turned out, however, Skuld was only getting emotional as a part of Goddess puberty, and her full powers were kicking in. Once that settled, she mostly dropped said crush. In the manga version of the story, she merely suspects that she has a crush on Keiichi and sets out to prove that she doesn't.
Played for Laughs in Crayon Shin-chan: Shin, who is in kindergarten, falls in love with college student Nanako Oohara; meanwhile his classmate Ai Suotome has a crush on him.
In Gunslinger Girl, Henrietta seems to have quite a crush on her handler Jose. This is never really built on, but remains Henrietta's most notable character trait, and is contrasted with Elsa's fatally disabling crush towards her handler.
Triela has a crush on her handler Hilshire. She refuses to reveal her feelings as she's well-aware that at least a part of her feelings are conditioned by the treatment that made her a Tyke Bomb, and also knows that he's not much more likely to be romantically interested in a girl half his age.
Sakura Taisen's Token Mini Moes all fit into this category: Iris (10), who wants Ohgami (19) to be her boyfriend; Coquelicot (9), also with a crush on Ohgami; and Rika (11), who's in love with Taiga (not sure how old he is — 18-20 probably?).
Asuna Kagurazaka (14) is crushing on Takamichi (mid to late 30's). May be subverted as Asuna is older than she looks and may very well be as old or older than Takamichi. She just doesn't remember it. However, Asuna getting turned down also has nothing to do with her age, oddly enough. Takamichi simply feels unworthy of love, especially from royalty. And it's actually not odd at all since she's at least three or four times his age.
Asuna also has a similar attraction to the mid-to-late-40s Eishun Konoe, the father of her best friend Konoka, and had a bit of a similar reaction the first time she saw Nagi in a dream. Given that they, also, adventured with her and had a hand in, basically, raising her, this may be feeling for them as parents (except Takamichi), misplaced due to amnesia.
As a kid no older than 15, Kurt Godel used to have a huge crush on Negi's mother Queen Arika. Now that he's in his 30's, he's still in love with her. Nodoka's Artifact says so.
Nagi treats Evangeline's crush on him as this the first time its mentioned. When she points out her age he turns it around that she's far too old for him and that it was still creepy.
Eve (who is assumed to be around 11) from Black Cat has a crush on Sven (30 years old). To the point where she actually feels a rivalry towards Train, wanting to replace him as Sven's partner.
Marie has a crush on the older Ageha in Psyren. Things get a bit complicated when Ageha travels to the future and discovers that, along with her Plot-Relevant Age-Up, she is still crushing on him.
Tomoe Marguerite from Mai-Otome develops a crush on a teen-aged Shizuru as a pre-teen girl, even going so far as to sneak onto campus to get a look at her. Several years later when Tomoe is 15 and a student in Garderobe, it becomes verysquicky when she sexually manipulates an adult, captive Shizuru (who is now a staff member at the school Tomoe attends) and basically rapes her..
Nanaka 6/17: Kuriko, a kindergartener, gets a crush on high-schooler Nenji because he saves her from some bullies and looks like her older brother, who is abroad.
Going by the official timeline, Asuka's thirteen until the last few days of the series, and Kaji has been her guardian for some time before the series begins. Her crush may or may not be a more recent development.
In the NGE world, the guardians get all the love. Shinji fantasizes about his own guardian, Misato. But, in marked contrast with Asuka, Shinji is thoroughly disgusted with himself for these feelings, which he never admits to anyone. And toward the end of the series, when a distraught and lonesome Misato suggests to an even more distraught and lonesome Shinji what seems to be an offer of 'comfort sex', he not only balks but soon thereafter runs away for good.
Jerk Ass guardians get love, too. As horrible as Gendou is to pretty much everyone, his ward Rei included (if not most of all), at the start of the series, Gendou seems to be the only character to whom Rei has developed any sort of emotional attachment. As the series progresses, Rei's feelings gradually transfer from Gendou to his son Shinji, and intensify enormously in the process. Which alters rather than alleviates the squickiness, since she's the clone of Gendou's wife / Shinji's mother, Yui.
And of course, RahXephon has 16 year old Ayato having a crush on 28 year old Haruka... Which turns out quite differently than in EVA, as she used to be his same age as well as his girlfriend. Well, before shit hit the fan and they were separated for 12 years..
Mika from Gungrave (who is about fourteen) develops one for Grave, who's saved her on numerous occasions and is also not just her bodyguard, he's also her mother's former sweetheart. However, Grave's also undead and is way older than her (he was about 29-30 at time of death and reanimation stopped his aging but still). It doesn't go much further than that, as Grave specifically tells her that all he can do for her is to serve as her Guardian.
In Black Butler, Angelina aka Madame Red was revealed to have harbored a deep Precocious Crush on Earl Vincent Phantomhive, Ciel's father. At the time, she was quite a bit younger than him. Unfortunately for her, he ended up marrying her older sister Rachel, Ciel's mother. And some years later, both Vincent and Rachel got killed..
While not as major as some, Game X Rush has Sayako, a 13-year-old Teen Genius, crushing on 19-year-old Memori who doesn't seem to notice. (Granted, he's a little preoccupied.) This continues three years into the future, when Sayako is 16 and Memori 22.
8 year old Rebecca Hopkins from Yu-Gi-Oh! has one of 15-year-old Yuugi. It's less Squicky in the Japanese version, where she's 12 years old.
In Durarara!!, Shinra Kishitani has been harboring an intense and very vocal crush on his Dullahan housemate, Celty, for the last twenty years. He's only twenty-four. Do the math.
His friend Shizuo Heiwajima, as a child, had a huge crush on a cute shopkeeper from his neighborhood. She got seriously injured when Shizuo had a psychotic breakdown while trying to protect her from thugs, and several years after that, he still considers the terrible incident as his greatest failure.
Hanamaru Kindergarten is about a five-year-old little girl's adorably bungled attempts to get her kindergarten teacher to love her. She's convinced he has a crush on her, since... he called her "Little Lady." Unlike Kodomo no Jikan, this plays its subject matter for laughs and d'aawwws.
Rita in Michiko to Hatchin is a ten-year old foundling with a Precocious Crush for the man who discovered her and adopted her into the circus he worked in. Since the object of her affections is about to settle down with a woman, she's intensely jealous. However, she gets over it.
In Tiger & Bunny, protagonist Kotetsu's 10/11-year-old daughter Kaede develops a crush on her dad's 24-year-old partner Barnaby after he saves her life in the second episode. Kotetsu's a bit annoyed about it.
Blue Rose/Karina is in her teens and harbours a massive crush on Kotetsu who is in his late thirties. When she discovers he is widowed and has a young daughter, she goes into a state of shock but by episode 25, she seems to have recovered and is intent on making Kotetsu fall for her.
In the 3rd OVA to the original Fushigi Yuugi series, Mayo falls in love with Taka at an ice cream parlor while she is in Junior High. Her unrequited feelings become a major plot point as she tries to rewrite the Universe of the Four Gods so that she becomes Taka's wife instead of Miaka.
Fullmetal Alchemist has May Chang, who at first has a crush on Ed...and then she actually meets him. From there her crush shifts to Ed's much more polite brother Al, who's around her same age. It is heavily implied that they end up together years later.
Mawaru-Penguindrum has Ringo, who falls for Keiju Tabuki when she's a little girl. He's old enough to be her schoolteacher, and is in fact the teacher of the Takakura brothers Kanba and Shoma. And her was the boyfriend of Momoka, Ringo's dead older sister.
In Tsukigasa, one of Azuma's young students tries to disrupt Kuroe's lessons because he has a crush on Azuma and sees Kuroe as his rival. It's Played for Laughs considering how worked up Kuroe gets over it.
Isami in Noein has a rather obvious crush on his teacher Ms. Yukie, which his friends tease him endlessly over. Several future timelines show him eventually getting into a real relationship with his childhood friend Ai.
The main character (who is 9 years old boy) and this 21 pro-golf player lady (21 years old) who took care of him for some time. Well they did get along quite well, so it's no wonder that they actually got married years later.
On of they students at the golf school in America had a really strong crush on his female teacher. It all started when he was brought to the school as a small boy and cried a lot. Said teacher tried to replace his mother (with whom he had little contact while in school), but the boy developed feelings for her which very different from those one has for his parent. In the end nothing came out of this crush.
In Magical Shopping Arcade Abenobashi, 12-year old Sasshi is this way toward fanservice girl Mune-Mune; which is ironic considering she's really his grandmother, who looks perpetually like her 19-year old self, thanks to a time paradox!
Naota Nandaba develops a crush on Haruko Haruhara in FLCL. It's implied that he's around 12 years old, and she's at least 19.
An interesting case, in that he only decides he loves her after she spends several episodes flirting with him and teasing him and basically doing everything short of molesting him to get him to notice her. Then when he finally responds to her advances she plays this trope straight, saying that he's too young for her and leaving him behind when she leaves Earth.
Garcia Lovelace (no older than 13) from Black Lagoon has a crush on his Mama Bear maid Roberta (mid-to-late 20's). Confirmed in El Baile de la Muerte, where he kisses her◊.
8-year-old Momonosuke in One Piece has a crush on 20-year-old Nami, who, true to the trope, remains oblivious and lets him sleep in her bed.
In Garden Of Words 15 year old Takao slowly develops a crush on the mysterious (to him) 27 year old Yukari Yukino. Although Takao wouldn't call it a crush, he is mature enough to admit it might be of that nature. This is incredibly awkward for Yukino, she having been forced out of her job as a teacher at Takao's school as a result of malicious false rumours about her reciprocating a crush from a different student.
A variation of this occured in X-Factor. Waif Prophet Layla Miller didn't act like she had a crush on Jamie Madrox, but several times told him, that they eventually going to get married. They did get together and eventually married after she received a Plot-Relevant Age-Up.
Sin City: John Hartigan, 60, saves Nancy Callahan, 11, from a pedophile. When he is set up as a scapegoat and sent to jail she confesses her love and promises to wait. When he is released 8 years later he discovers that she kept her promise. While she is technically legal, he still refuses to make a move on her because of the age difference and their history.
In Batman, Damian Wayne, who is at best, biologically twelve (New 52 Damian definitely has accelerated growth, and five years old chronologically, at best) has several: Cassandra Cain, Katana, Stephanie Brown and Supergirl.
This is also what the other heroes believed when he and Stargirl started dating since they looked like a teenage girl and a late-20s man instead of two teenagers. The eventually broke up to maintain Billy's secret.
A late 70s issue of Josie and the Pussycats centered around a little boy who appeared to be stalking Josie and Melody. When Alexander finally apprehends him, the young stalker tearfully admits he had a crush on Melody, who is so flattered she kisses the boy smack on the lips. The kid launches off into space.
X-Men: The young X-Girl Megan Gwynn/Pixie developed a crush on team leader Cyclops during her earlier appearances, and it occasionally pops back up from time-to-time. Scott meanwhile seems to view her as a daughter (something his X-Men: Destiny self outright states when she dies), and given the age gap there's little-to-no chance of them going anywhere... but her and the Young!Scott that came to the present following Avengers vs. X-Men seems to be a slowly growing Fan-Preferred Couple in some circles.
Tempus, a teenage mutant, also developed a crush on Cyke, pretty much the moment she met him. She didn't hide it particularly well, and everyone knew how she felt about him. However, even with her Plot-Relevant Age-Up, Scott still appears to be in his forties (this is outright stated), while Tempus is at best in her very early twenties.
Young!Jean also starts to have a crush on Cyke since he's the man she hoped Young!Scott would grow up to be. Cyke shuts this down immediately since he knows it's inappropriate on so many levels.
Frequently forgotten (and perhaps since retconned) is that Susan Storm knew and had a thing for Reed Richards since he was a college undergrad...and she was thirteen. All in all, that worked out surprisingly well.
Cypher of New Mutants nursed an unrequited crush on Psylocke.
Rainbooms and Royalty: A recurring plot point is that when filly Rainbow Dash moved to Canterlot to become Celestia's student, she met Shining Armor when he became a member of the Royal Guard and started crushing on him. Hard. And obviously. At the end of the story, Shining finally talks to Dash about it, and gets her to accept that he only cares for her like a sister, and she seems to move on.
Until the second sequel, Hot Heads, Cold Hearts, and Nerves of Steel, reveals that she still has lingering feelings for him. This becomes a serious source of tension due to the Mane Six being accompanied by him and Cadence on their mission.
"Seeds of Magic", a recursiveAlternate Universe spinoff of the Pony POV Series, has something similar happen to that universe's version of Applejack — she meets Shining Armor due to befriending Twilight in school and develops a crush on him. She claims to have long since gotten over it, however.
Deconstructed in the Ben 10Hero High Sphinx Academy. Lord is able to detect the old scars in Gwen's heart when she had feelings for her cousin Ben back when they were kids. It is revealed that due to her disgust to these feelings she hurt him in response when he was just trying to cheer her up after a bad day at school, which is the reason why they have not gotten along for nearly a decade after. Lord nearly cripples Gwen mentally revealing this fact to her.
The Dark Knight Saga fanfic "What No One Else Had Seen" implies that nine-year-old Harley may have a little crush on Jonathan, who is sixteen. The fic, being about the pair finding a dead body, manages to be sweet and macabre at the same time.
In All-American Girl, Sam Martinez reveals that he has had a crush on Princess Celestia since he first saw her at age 11. He gets the chance to act on it twenty years later.
In The Stalking Zuko Series, Katara had a crush on her father's friend Bato when she was 12, a mere two years before the start of the story. She got over it quickly, and as such, hopes that the 12-year-old Aang will get over his crush on her. The author also points out that she doesn't think much of this trope, saying that people don't wind up with those they're interested in when they're 12.
Jenny in the movie Big Fish. When she meets Edward Bloom, she's eight and he's eighteen. She tells him that once she gets older, the age difference won't matter as much. Years later he meets her again, him now married and her divorced.
Jenny: I was 18, he was 28. Turns out it was a big difference.
While a borderline example due to the ages involved, this trope is the main plot point of 1979 movie Sooner or Later.
Blank Check has a Squick-ish moment in that the young boy actually gets a brief on-the-mouth kiss from the adult woman at the end, who tells him to look her up when he's older.
Teenage girl Megan has a crush on the at least thirty-something Preacher in Pale Rider.
In The Sandlot, Michael "Squints" has a crush on the lifegaurd at the swimming pool, knockout blonde Wendy Peffercorn. Actually all of them do, but Squints is the only one who acts on it. He can't swim, so he jumps into the deep end of the pool so she'll perform CPR. It works. The kids all get banished from the pool forever. Once they're grown up, Squints and Wendy get married and have 9 kids.
Also in Jack when the titular character gets a crush on his school teacher. Played with and justified since he suffers from a disorder that speeds up his aging four-fold (so he looks and appears 40 when he's actually 10 at heart), he sees it as OK because he looks like a grown-up (which eliminates girls his own actual age). The teacher understands this, but still turns him down, because he is ten years old at heart and it would still be wrong regardless of what he looks like.
In the film version of Jurassic Park, tomboyhacker Lex Murphy clearly has a crush on paleontologist Alan Grant, even before he saves her life. In the novel, Lex is much younger, so this subtext is absent.
In Ang Pagdadalaga ni Maximo Oliveros (The Blossoming of Maximo Oliveros), 12-year-old Maxi, a boy from a family of petty criminals in the Manila slums, falls in love with a handsome rookie cop. They become friends and the cop, whose sexuality is left ambiguous, grows quite fond of Maxi, but nothing happens between them except the cop telling Maxi he's pretty and stroking his hair and Maxi stealing a quick peck on the cheek.
The little penguin Arnold in Surf's Up has one for local lifeguard Lani, to the point where he routinely attempts to drown himself, just so she can rescue him.
Neil in Mysterious Skin. It's not so much a crush as it is an instant 'sledgehammer' of desire he feels upon seeing his baseball coach for the first time. And unlike most other examples of this trope, it does not go unrequited. Horrible, horrible, horrible events ensue.
Disney's Robin Hood has Skippy's sister remarking how handsome Robin was. Robin never addresses it and it was only brought up in that one scene.
In Malena, 12-year-old Renato becomes obsessed with the titular Malena, a woman whose husband has gone to fight in the military overseas and is presumed dead. It becomes at least a little disturbing when he develops Stalker with a Crush tendencies, and even has sex with a local prostitute while fantasizing about Malena.
Nick, the main character and focus of the titular The Crush, thinks of Darien's infatuation with him this way...at first. His coworker/girlfriend is the first one to realize that Darien is Ax-Crazy and dangerous, though Nick gets there soon after.
Edison has one of these in Valentine's Day, recognized and redirected near the end by the target of his crush.
In The Professional, the adolescent Mathilda has a crush on her savior and mentor, Leon. The original cut of the film makes her crush less innocent, and she actually propositions him for sex.
In My Girl, the lead develops a crush on her teacher - and finds out he's engaged on the same day as her best friend's funeral.
Used for a throwaway joke in Raiders of the Lost Ark. One of Indy's female students has penned "LOVE YOU" on her eyelids so that they're visible when she oh-so-fetchingly bats her eyelashes at him. Indy loses his train of thought in mid-lecture and is visibly unsettled.
There's also a less lighthearted treatment of it in the film. Marion was the daughter of one of Indy's mentors, and had such a crush on him, which apparently led to the two becoming involved. The fallout from that resulted in the destruction of Indy's relationship with Marion's father and quite a fair bit of bitterness on Marion's part, hence why when Marion sees Indy one of the first things she does is hit him and scream "I was a child! I was in love! It was wrong and you knew it!" Word of God is that she was definitely underage at the time.
Crazy Stupid Love: Robbie has a longstanding crush on Jessica, his babysitter. He's in middle school (so about 12) and she's about 17.
Done in an inadvertently disturbing manner in Blank Check. The main character tricks an adult bank teller into going on a date with him and later, she even kisses him on the lips after agreeing to wait a few years.
The Lorax has 12-year-old Ted crushing for high school girl Audrey.
9-year-old Phaedra has one of these on 18-year-old bull-leaping star Theseus in Mary Renault's The King Must Die - especially unfortunate because by the sequel she has grown up to be a full-fledged Femme Fatale.
Played with in The Time Traveler's Wife: the title character makes an awkward attempt to seduce her future husband when she is sixteen and he is visiting from the future. He refuses, telling her that he can't because he has a wonderful wife who he loves very much. She is crushed, even though she knows that she is (will be) that wife.
The Door into Summer. An adult male time traveler is friend/honorary uncle to an 11 year old girl, who falls in love with him. He goes into cold sleeptwice into the future. The girl waits until she's 21, then enters cold sleep herself, to awake when he returns.
In Podkayne Of Mars, Podkayne's younger brother develops a crush on a lady traveling with them on the space voyage to Venus.
A similar situation happens in The Cat Who Walks Through Walls, except she joins a time-and-dimension-traveling agency and works for them until she ages up enough. From her crush's perspective, it was only a few days.
The main plot of Joy School by Elizabeth Berg. Jimmy takes it extraordinarily well, all things considered.
Although she's not seen in the actual story until she's an adult and the Queen of Elenia, The Elenium trilogy by David Eddings indicates that Ehlana had one of these for Sparhawk from the age of seven onward, sparked because he was one of the few people she could truly trust. Of course, they end up married despite the twenty-odd-year age difference, so it was a bit different from most crushes of this sort.
Of course, when they later have a daughter, she announces by age four who she's going to marry. Considering what she is, she probably will.
Jean-Jacques Rousseau (yes, that one) had the stones to publicly admit to this in one of the most celebrated autobiographies of all time. Bonus points for deliberately misbehaving so his teacher would spank him.
There's a form of this in Starfighers of Adumar, where dueling champion Cheriss gets a crush on New Republic hero Wedge Antilles. Compared to Adumari pilots, he's practically a god. He considers her to be somewhat younger than what he'd call adult, although she is risking her life in blastsword duels. It's never stated how old she is; in a previous book Wedge treated sixteen-year-old Gavin Darklighter like an inexperienced adult, but he called Gavin "kid", and he never does that to Cheriss. He's embarrassed by the crush and tries to ignore it. She sees Wedge's Old Flame as competition of sorts, and when Wedge actually hooks up with his old lover again, Cheriss tries to commit suicide by honorable combat. Wedge talks her out of it while finally getting out his dislike for this Proud Warrior Race society.
Thirteen-year-old Tash Arranda in Galaxy of Fear meets nineteen or twenty-year-old Luke Skywalker and takes an immediate liking to him. He carries a lightsaber like the Jedi Knights she so idolizes, he's kind to her and doesn't dismiss the weird feelings she gets like everyone else she's ever met, and she feels like she's been waiting all her life to meet someone like him. Tash immediately says in the narration that it's not a crush, she is too old for them now When he leaves, this happens.
An electric tingle rose up Tash's hand as Luke shook it. The tingle lasted long after the Millennium Falcon had blasted into the sky.
In Harry Potter and the Chamber of Secrets, twelve-year-old Hermione has a crush on Professor Lockhart, but then, so do most of the girls in Hogwarts (not to mention Molly Weasley and the other mothers.)
In Linnea Sinclair's Hope's Folly, Rya was ten years old when her father brought one of his subordinate officers home for dinner. While Philip vaguely remembers her as an obnoxious little girl hellbent on bothering him, she remembers him as the ultra-cool friend of her father who took the time to teach her how to shoot properly. When they meet up, in her mid-twenties and his late-forties, Rya's crush reignites and she pursues a May-December Romance with him.
Similar to the above example, Glokta's backstory in The First Law makes mention of him, the dashing war hero, visiting the home of his subordinate and friend, Collem West. Little sister Ardee West was just a child at the time, but thought Glokta was the man of her dreams. When they meet again some ten years later, the child he vaguely recalls has grown up beautiful, he starts falling for her, and she...well...two years of torture make a man somewhat less dreamy, and she's more interested in Jezal than a girlhood crush. Jezal kicks her to the curb in the end, though, and Glokta gets the girl. Kind of.
In Hilary McKay's third book in the popular Casson Family Series, the implication in Permanent Rose is that Rose (who is only eight/nine at the time) has a crush on Tom Levin, who is at least twelve/thirteen at the time, but she isn't aware of it herself that she has a crush on him, whereas everyone else in her family is cognizant of it.
The narrator of Jacob Have I Loved, at the age of fourteen develops a crush on Captain Wallace, a man who, at seventy, is older than her grandmother.
In The Roman Mysteries, Flavia, at the age of ten, has a crush on Publius Pollius Felix, who is in his thirties, married, has a daughter her age, and is later found out to have slept with most of his slave-girls and a good deal of other women, causing his wife to try and poison herself. Eventually she sees him for what he really is and gets over him.
While the age difference is not that huge, in the Wind on Fire series, eight-year-old Pinto has a crush on Mumpo, who is fifteen (legally able to be married in the world the two live in) and in love with her older sister Kestrel. She gets him in the end after Kestrel "dies", though.
Fourteen year old Evelyne, from Malevil, has a severe infatuation with Emmanuel. Unfortunately, she gets possessive, Emmanuel bows out of his Apocalypse-induced Polyamory relationship, and he becomes accused of being a Lolicon.
In Ronald Frame's The Lantern Bearers, a 14-year-old boy soprano spends the summer singing for a young composer and becomes attracted to him. When the boy's voice suddenly breaks he is summarily kicked out — shades of Benjamin Britten's boys — and in revenge falsely accuses the composer of having "touched" him, with tragic results.
A Song of Ice and Fire has Bran crushing on Meera. She only has about 4 or 5 years on him, but since he is only nine, a few years makes a very big difference. In any case, his crush has the archetypal innocence and Moeness of this trope.
Depending on how much you consider her a child (she is 12 but the Medieval Fantasy setting makes this old enough to marry,) Sansa could be said to have one for Ser Loras and the Hound. Possibly, you could say she has a Precocious Crush on Ser Loras, (since she thinks of him in childish fairy-tale terms,) but a more mature sort of attraction for the Hound, (who has made her his Morality Pet, but simultaneously terrifies her and arouses her pity, leaving her very confused about her feelings for him).
Cersei Lannister was smitten with Prince Rhaegar Targaryen when she was ten and he was seventeen. She never forgave her father for failing to get her betrothed to Rhaegar and hated Robert Baratheon for killing him in battle. (After the war when her father made a political marriage between Cersei and Robert, that relationship worked out just about as well as you'd expect.)
In Connie Willis's Blackout, the adolescent Colin explains to Polly that he hopes through some Time Travel tricks to end up her own age. At the end of All Clear, he's done it, not for the crush, but in a desperate attempt to save her and another time traveler from death.
In Skulduggery Pleasant: Dark Days, Davina Marr mentions Valkyrie's crush on Skulduggery. Marr mocks Valkyrie's crush on her much, much older mentor and best friend again in Mortal Coil. Valkyrie doesn't confirm it, but neither does she deny it.
Legacy of the Dragokin: Benji is ten and has a crush on the fifteen year old Lydia, who is functionally an adult because she's an officer in her country's military.
In The Dresden Files, Molly Carpenter had this for Harry. Harry is fully aware of the reason for it, and provides the current page quote on Like Parent, Like Spouse when he gently tries to explain the situation to her. Unfortunately, rather than growing out of the crush, it changes into definite sexual feelings when she's a teenager and it eventually becomes genuine unrequited love when she's in her twenties. By this point she has matured enough to let her relationship with Harry stay platonic, and consequently Harry assumed that she had gotten over her childish crush and was surprised and saddened to discover the depths of her feelings, since he knew he could not reciprocate them.
Though with the shift in power dynamic between the two as of Cold Days, Harry himself doesn't rule out the eventual possibility of something happening between them.
Julian Desjardin's novel White Lightning has this as part of Detective Andrews' backstory, Played for Drama. He apparently spent a year pining over his sixth grade teacher, and when not very gently turned down, came to the conclusion it was because he 'looked wrong'. Thus began his lifelong obsession with passing for white, including a name change taken from a book she'd assigned him to read. Twenty years later, in 1927, she meets him again, and realizes the damage she's done when she addresses him by his Korean birth name and he legitimately doesn't react to it.
In Buffy the Vampire Slayer, as part of the false memories created by the Monks, Dawn has had a crush on Xander for years (it likely started in Season 1 or 2 where she would have been 10 or 11). As they're together as of Season 8.
Glee: Rachel spent an episode infatuated with Mr. Schuester. It didn't last past that one episode. Suzie Pepper, on the other hand...
In many an episode of Frasier, Frasier's 8-year-old son Frederick exhibits a huge crush on Daphne, much to Niles' chagrin.
Neighbor boy Glen in Mad Men develops a crush on Betty Draper. This winds up greatly embarrassing Betty when she humors the crush a little bit.
In House, the 8-year-old brother of one of House's child patients gets an enormous crush on Cameron. It starts with him stealing flowers for her, then he grabs her butt, and later he attacks Chase. This eventually leads to House solving the case, as he is wont to do.
There's also the little girl with cancer who manages to get Chase to kiss her.
Lizzie develops a crush on her soccer coach in one episode of Life With Derek.
Kevin had an ongoing crush on his teacher, Miss White/Mrs. Heimer.
Sam of Quantum Leap was attracted to his piano teacher as a young teenager. In the episode "Catch A Falling Star", he leaps into an actor working on a production with her, and attempts to use the opportunity as a second chance for himself. In other episodes, he also mentions having had crushes on his kindergarten and first grade teachers.
Samantha Puckett on iCarly revealed her crush on Spencer in the episode iGet Pranky. Although she's seriously close to the age where the "precocious" part doesn't apply any more.
JJ Powell from No Ordinary Family has had one on Katie since episode 7. At least, this is the first time it's mentioned.
In season 3 of Happy Days, Joanie develops a short-lived crush on Potsie after, during a performance rehearsal, he sings "Put Your Head On My Shoulder" to her.
Punky Brewster was an established tomboy, and in season three (first syndicated season) she developed a crush on a boy some seven years older than her.
In the Married... with Children episode "Life's a Beach", the Bundys go to the beach and Bud makes a bet with Kelly, that he will "get a squeeze" before her. As usual, he's rebuffed by women, but a little girl becomes enamored with him after he fixes her bucket, and calls him her boyfriend; thus he technically wins the bet.
In the Swedish kids' TV series Ebba och Didrik, 12-year-old hopeless romantic Didrik falls hard for 23-year-old Yrla. They become friends, but she's definitely not interested in him that way, and may not even be fully aware of his crush.
On 3rd Rock from the Sun, Tommy got a crush on his music teacher Miss Frost, with the aliens not realizing how inappropriate a relationship between them would be.
Tommy: Well, I met this woman that I really like and I think she likes me, but she's a little older. Thirty-one. Dick: Tommy, do you really think a woman of that age would be interested in you? Tommy: Sure. Dick: Wow, good job!
This example is complicated by Tommy technically being older than Miss Frost since he's the senior member of the crew.
Stargate SG-1: In "Birthright", Ny'sa, a young, female Jaffa on the cusp of puberty, develops "quite an affection" for Daniel, in the words of her older sister. Who doesn't have a crush on Daniel, though?
Played for Drama in "Heat", where then-16 year old Clark (so he's just barely passing for this trope) develops a crush on the new Hot Teacher, who's currently engaged to his best friend, Lex Luthor. However, it turns out the teacher is a Gold Digger with the power to make men fall so much in love with her they do whatever they can to please her, which she usually uses to make boys that fall into this trope try and bump off the rich man she's just tricked into marrying so she can make of with their millions, leaving them to take the fall.
In "Infamous", a little girl deliberately jumps off a building so Clark will catch her, then kisses him on the cheek.
Given respective ages, almost any female (and at least one male) companion for the Doctor in Nu Who. In the literal sense, Amelia Pond and Mels Zucker for the Doctor.
Hannah Montana: The first episode of Season 2 has Rico crushing on Miley, even going so far to manipulate her into going out with him because he knew Miley was scared that "He knows her secret and will spill it out" (she thought that the "secret" was being Hannah Montana). In the end, turns out that the secret was She still has her teddy bear with her, despite being in high school.
Lizzie McGuire: The episode "Working Girl" had this in effect when Matt was depressed, then Miranda gave him advice, and then he starts falling for her. This went as far as asking her on a date.
A.N.T. Farm has Fletcher immediately liking Paisley whenever the latter notices him. Examples are in the episodes "TransplANTed" (as shown in the picture above) and "ManagemANT", but luckily, Chyna doesn't seem to mind. Doubles as a "just for his adorableness" Shotacon in Paisley's part.
The Suite Life of Zack and Cody has this with Zack over Maddie throughout the show. By On Deck, he got his kiss from her. One of the most memorable moments is in the episode "A Prom Story" where they shared a prom dance.
Also from On Deck, the 8-year old prince of Liechtenstamp crushing on Maddie. He even was near to marrying her, too! On this same same episode, Zack still had feelings for Maddie, but it evolved into a Likes Older Women situation.
Shake It Up had this in one episode's B-plot, where Ty is teaching Flynn how to attract the girl he likes. The said girl is older than him and is portrayed by the same actress who plays Paisley in the A.N.T. Farm example above (Allie DeBerry).
On House, a young boy's overly aggressive pursuit of his crush on Cameron is yet another datum for the Case of the Week.
Luke is this to Jessie... sometimes. He also did this with Shaylee Michaels in "Jessie's Big Break".
In the first episode of Modern Family, 10-year old Manny writes a love poem to a 17-year old girl.
Manny also has a crush on 16/17-year old Haley Dunphy. No, the fact that they're cousins (by marriage) doesn't bother him.
British satire show "Big City" (a satire of american preteen shows) features Liam Youngs, an 8 year old kid who has a huge crush on his older sister's friend, Mia Sanders who's 16. In one episode, Liam tricks Mia into going on a date with him.
Crash And Bernstein has Pesto, about age 12 is this towards Amanda who is 16 and clearly older than him.
Liv and Maddie has this one time with Parker having it towards Liv's BFF South in "BFF-A-Rooney", complete with jealousy with he sees South flirting with Diggie.
Steve Wariner's "I'm Already Taken" uses three adaptations of the title phrase, the first relating to the narrator pursuing a woman who is "already taken" by another. By the time they get married in the third verse, their son says "mommy, will you marry me?" in an innocent context, and she repeats the title to him.
In WHO dunnit, eight-year-old Trixie develops a crush on her father's business partner, Tony, after they enter a deal to open a hotel-casino together.
Teen example: In Grease, Marty Maraschino has a crush on (and, it's implied, possibly a brief fling with) Vince Fontaine, the master of ceremonies and judge for the televised dance contest. She's about 17; he's old enough to be her father. In the film adaptation, she also has at least one, and possibly a series, of US Marine boyfriends; she clearly likes older men.
Persona 3: The subject of the Hanged Man Social Link is a troubled-yet-adorable eight-year-old girl whose parents are going through a divorce. Once you reach a certain stage, she decides that she's going to get married to the protagonist when she's old enough. Neither you nor the protagonist have much say in the matter. Not like it matters that much in the end since the protagonist dies.
In Persona 3 Portable, should you choose to play as a female, the Justice Social Link is changed to be Ken Amada. And over the course of the social link, Ken develops a crush on the main character, which the player can choose to reciprocate.
Also Genis' crush on Presea in Tales of Symphonia is half this. It starts when he thinks she's the same age, but his feelings don't change after he discovers that she's older. It's also downplayed due to an event in the plot. Presea's aging was suspended and she lived like an automaton in the interim, so she didn't age mentally either.
Pearl from Ace Attorney seems like this on paper, but she doesn't have a crush: she's a Shipper on Deck. And pretty willing to wound Phoenix for it.
In the first game, flashbacks and diary entries reveal that Etna developed one as a child on the first person to show her kindness, King Krichevskoy. As such, she absolutely hated his wife, and when Laharl was born, she had no idea what to think of him.
Latooni's crush on Ryusei seems to invoke this in Super Robot Wars Original Generation at times, but the fact that she's only three years younger than him (14 and 17 respectively) means it may not be like that forever (see also Mai, age 16, but actually shorter than Latooni). Shine's crush on Rai, however, is played fairly straight.
It may not be an actual crush. Put it this way: what would your reaction be to seeing someone of the opposite sex in his/her birthday suit? Sure the other males didn't react this way (Garr comes to mind, albeit somewhat justified as Deis was kicking his ass while naked) but the reaction can still actually be logical. Still inevitably hilarious if Nina was in the party during the scene.
A subversion from Fate/stay night. Ilya looks like this at first, appearing to be perhaps ten and obviously displaying a good deal of affection for 18-year-old Shirou. However, she turns out be slightly older than he is... and her idea of 'affection' is seriously messed up. Plus, her completely genuine affection stems from Shirou's foster father Kiritsugu being Ilya's biological father, though she has no intention of telling him that.
On the other hand, he appears to know in Hollow Ataraxia at least about the way they're linked, though he still treats her as a little kid. Which is okay because she definitely acts like one. However, there's a genuine example of the trope in that Taiga used to have a huge crush on Kiritsugu which caused her to initially get along poorly with Shirou. Given that she's only 24 now, he died five years ago and she had that crush for a pretty lengthy amount of time, you can guess that the crush started when she was no older than middle school age.
Lumina from Harvest Moon: A Wonderful Life apparently has a crush on you. In the PS2 version she 18 and is a potential bride, but in the Gamecube version she's about 11 and is a potential bride for your son.
Word of God is she's fourteen in AWL. She's sixteen in the Japanese version of Special Edition.
May, granddaughter of the local animal rancher in Back To Nature and Friends Of Mineral Town has her crush object, Pete - the player character.
In Golden Sun: Dark Dawn, a later cutscene mentions that Rief's sister Nowell is off pursuing a crush on Piers, about whom the least we can assume is that he's older than her mother, if not much more so. The youthful design of Golden Sun characters does mean that Nowell kind of pushes the "child" aspect of this trope, but it fits otherwise.
In the first Golden Sun, a young girl NPC in the town of Altin would try to kiss Isaac if you talked to her after defeating the Living Statues plaguing the town.
You defeated the monsters? Let me thank you... with a kiss!
In the Sonic the Hedgehog series, Amy Rose, an eight-year-old who, has a huge crush on Sonic, who is sixteen. Later after a half-retcon-half-timeskip in the series they are 12 and 15 respectively.
Cute catboy Leon has a crush on all of the girls in Star Ocean: The Second Story. How it gets resolved depends on who you have him talk with.
Mass Effect: Liara's feelings for Shepard (age 29 in the first game) can be interpreted this way. While she is 106, she is "barely more than a child" by Asari standards. In human terms that would make her about 19 or 20 years old.
Speaking of whom, the final DLC story implies Grunt has a minor crush on Liara. Grunt is a krogan designer-baby who was "born" as a teenager or young adult, with his memories and vocabulary already implanted.
Tiny Tina of Borderlands 2, explicitly said to be thirteen years old, displays a certain amount of interest in Maya (twenty-seven years old) and Moxxi (age unknown, but she has adult children).
This can potentially happen in Fire Emblem Awakening, if either Ricken or Donnel (both in their very early teens) develop feelings for any girl older than them. (Including a Female Avatar with Build 1 or 3, which make her look like in either her late teens/very early 20's or mid/late 20's respectively.)
And if you make Lissa (also in her early teens) and probably Maribelle (early-to-mid teens) support romantically with an old enough guy. (Again, including a Male Avatar with Build 2 and specially 3.)
In In Your Arms Tonight, some laughs are had at Koichi's expense thanks to the prepubescent son of one of the protagonist's close friend, who is bold enough to consider himself a rival for the affection of Koichi's thirty-two-year-old wife. The lady in question and the boy's mother laugh it off; Koichi is considerably less amused.
During Prince Keith Alford's sequel route in Be My Princess, one of the boys at the orphanage where Keith and the protagonist are doing volunteer work develops a crush on the protagonist, who is in her early twenties. To the protagonist's bemusement, Keith insists on taking it seriously, arguing that to do otherwise would be an insult to the boy's feelings.
Sandra and Woo is about this, much of the time, verging on Squick at times since the characters claim to be 12 or 13 but the situations can be somewhat old for that scenario
In Captain SNES: The Game Masta, Relm has such a crush on Sabin. The implications of this are heavily lampshaded, but Sabin is freaked out by Relm (due to the Sketch Glitch, he thinks she's a Reality Warper). When another young girl (who turns out to be a genuine Reality Warper) responds with more interest to Sabin being a prince than Edgar being a king, Sabin is not pleased.
Life of Maid (a Touhou comic where most of the characters are child versions of themselves) demonstrates the Unfortunate Implications of the trope with its Spinoff Babies (where the ages are reversed). Chibi Alice and Patchouli competing for adult Marisa's attention? Adorable. Two grown women stalking a young girl? Creepy as fuck.
The next-door neighbor's son in the webcomic Out at Home has a crush on Katie's best friend. He's 10; she's 17.
In an episode of As Told by Ginger, Ginger (12-ish) attempts to ask her teacher on a date with her. While competing in a school quiz competition. Which is being televised. Yikes.
Not to mention her obsession with Corey magazine (and the hotline) in earlier seasons, all full of boys who were at least in their teens. One example in the "Brother From The Same Planet" subplot, when Marge found out about Lisa's phone calls to the hotline, she revealed to Lisa that she was in the same situation in her childhood when she had a crush on Bobby Sherman:
Marge Simpson: Oh, honey, I know how you feel. When I was a girl, I had a crush on Bobby Sherman...
[Lisa bursts out laughing]
Marge Simpson: [annoyed] The point is, I want you to stop making these calls!
Lisa Simpson: [serious] All right, Mom. I promise you, you will never be billed for another call.
Bart also had a crush on new neighbor Laura Powers, who was in her mid teens. When he found out she was going out with Jimbo, one of the bullies who picks on him, he arranged a plan to break them up. It was successful — by the end of the episode, Laura had broken up with Jimbo and even told Bart that she would date him if he were older. The character was never seen again.
In one episode, in regards to Marge, Milhouse says "She's HOT! ...sorry that just slipped out."
Also happens in "The Devil Wears Nada" with Nelson and Milhouse looking at a pin-up calender featuring Marge.
In one episode, Chris has a crush on his substitute teacher.
Peter: Our son... would like to plow you.
In an episode of Foster's Home for Imaginary Friends, Mac (8) and Bloo (5) and some random imaginary friend and a pizza delivery guy develop a crush on Frankie (22). Mac and Bloo's 'feelings' for her are referenced a couple more times in later episodes.
In the Peanuts cartoon, A Charlie Brown Valentine, Linus' crush for Miss Othmar is seen, but then cooled off quickly when he sees his teacher ride off with her boyfriend. Cue Linus chucking every chocolate from a big heart-shaped candy box over the bridge... and Snoopy and Woodstock getting a free treat for every toss!
In Codename: Kids Next Door, Numbuh Four started to get a crush on his fourth grade teacher, Mrs. Thompson. Unfortunately, that turned out kind of weird later, when it turned out she was the Were-Dog Queen, cursed with lycanthropy by her jealous ex-husband. (He was able to break the curse in the end.)
In Johnny Bravo, Susie is a 10 year old girl who clings to Johnny at every possible moment. He usually must go to great lengths to get rid of her.
Though soon after the art style shift happened in the show, her implications of having a crush on him disappeared. Likely as it would be mildly creepy to have a girl infatuated with the town lecher.
My Little Pony: Friendship Is Magic has Spike, who is sort of like an adopted son/brother to Twilight Sparkle, and in personality is much like a preteen. He has a major crush on Rarity, who is clearly an adult (and a fashion designer of great renown, much more renown than you can get if you're only recently an adult.), the moment he saw her.
In Home Movies, Jason develops a crush on the school nurse.
Finn (13) of Adventure Time was crazy about Princess Bubblegum (18... maybe) until he fell for Flame Princess (13). When Bubblegum is temporarily aged down to the apparent age of 13 due to a Lich-related phlebotinum malfunction, she appears to reciprocate, but upon return to the effective age of 18 Finn is back in the Friend Zone.
Buttercup in the Powerpuff Girls episode "Buttercrush." She has a crush on Gangreen Gang leader Ace, which lasts up until she sees the Gang about to kill Blossom and Bubbles. The short-lived crush is even lampshaded in a comic book story ("Five Green Vandals," issue #16).
They're full-on dating in the game FusionFall, though she doesn't seem much older than 13.
In Birdz, Eddie Storkowitz has one of these on his teacher, Miss Finch.
Happens to Arnold of all people in Hey Arnold! when he falls in love with the substitute teacher, especially when he overhears her say she's going to marry him (when in reality, she meant her same-age boyfriend, who happened to be named Arnold).
He also crushes on Ruth McDougall a few times early in the series, despite her being a sixth grader while he was still in the fourth, and it ended because he and Ruth are different. And then there was that one Beach Episode with one-time love interest two-timing him...
This may or may not count but that one episode where Gerald's little sister Timberly (who's about five or six years old) had a crush on Arnold (who's nine). The age difference is small but Arnold acts much more mature than Timberly.
Alongside Arnold, Gerald had one too in the episode "Sixth Grade Girls".
All four Turtles in the original cartoon have evident crushes on April, who is 28 in that version. We're never told how old the Turtles are, except that they're teenagers.
Many of the South Park boys fell for a cute substitute teacher in an episode. She's a lesbian, though.
Moral Orel: 11-year-old Orel develops a crush on Stephanie, who works at the town's only sex shop. She turns him down nicely at the end of the episode and they retain and Intergenerational Friendship. Even if there weren't an age gap, Incompatible Orientation would have set in. In the second season, Doughy develops a crush on his teacher Miss Sculptham, who ends up taking advantage of him so he'll (and later by extension, Mr. Creepler) keep buying her expensive gifts.
The Secret Saturdays: The 11-year old Zak has a crush on Abbey Grey who used to be his babysitter. This causes some serious jealousy issues when she starts dating his uncle Doyle.
Dexter's Laboratory: Dexter has a crush on his teenage babysitter in one episode, and it didn't end well when he aged up, making the result... not so great, and a punch to the face by her boyfriend!
You can add Arthur Read to the list of preteen boys with crushes on teenage babysitters.