Dragon Ball Z: Goku gives a particularly boastful one when he first sees Frieza's Final Form. He soon comes to regret those words.
Fullmetal Alchemist: Edward Elric. His title means that people confuse him with his suit of armor brother. And being called short is his Berserk Button. When Mei Chan meets Edward for the first time, her dreams are shattered when she learns Fullmetal Alchemist does not meet her fabrications of the handsome, tall, and princely figure she imagined him being.
Black Cat: This happens occasionally to Train Heartnet — mostly in the manga. Having been the strongest member of Chronos and a legendary and feared assassin, many people are shocked when they find out how young he is. Of course, an extreme example of this occurs when Train gets transformed into a child after getting hit with the Lucifer bullet. Chronos assassins who want to kill him are rather shocked when he claims to be the Black Cat.
In Baccano!, a couple of Russo-affiliated thugs are given the task of hunting down a man who managed to single-handedly destroy and rob eighteen of their speakeasies in a single night. And just who is that implacable, One-Man Army of Badassery, you might ask? This guy◊. No, not the one with a gun. The guy in the vest who's bawling his eyes out.
Katekyo Hitman Reborn!: This tends to happen to Tsuna. He's supposed to be the 10th Generation Vongola Boss (against his will, of course), but he's only 14, and is very scrawny and rather pathetic looking. A lot of people say variations of this phrase, and find it generally hard to believe. Interestingly enough, this phrase isn't explicitly said by Spanner, but implied when he gets Tsuna some prisoner clothes, and remarks in surprise and exasperation that even size small is too big for him.
In Full Metal Panic!, this happens to Sōsuke during one of his missions where he had to work with another group of soldiers to kill Gauron. When they first see him, many of them ask why there's a kid here. They find it extremely hard to believe that he's the one assigned to assist them, and find it an insult that Mithril would send a "child" to help.
In Death Note, the police are surprised when L turns out to be a scrawny guy in his early twenties.
In at least the anime version, Milly and Meryl are unable to recognize Vash the Stampede at first because pretty much nothing about him appears anything like the infamously destructive gunslinger they expected. Admittedly, he is tall and his hair is too, but he's far from the tallest person on Gunsmoke (and his hair isn't the biggest, either), and, more importantly, he's a staunchly pacifistic goofball who tends to run around screaming in terror, tripping over his own feet on occasion, flirting with girls and wolfing down doughnuts.
The only things known about Vash is that he's tall, has blonde hair, and a red coat. Some other details occasionally pop up, but those are as often wrong as right (such as him using a boomerang) from seeing people mistaken for Vash.
The first episode of the anime focuses on several bounty hunters who become suspicious of each other as they try to figure out who the real Vash is. Conversely, in the manga, the cities are festooned with wanted ads featuring his picture, so this isn't an issue.
When Shuji from Durarara!! set out to interview the most fearsome man in Ikebukuro, he was expecting to find a large, over-muscled monster of a man covered in scars and tattoos. What he got was Shizuo, a slim, quiet young man who insisted that he hated violence. Of course, nobody told Shuji that Shizuo had both a Hair-Trigger Temper and Super Strength, and thus Shuji found himself tossed around like a baseball after asking exactly one too many questions. Ironically, Shuji notes that the only thing that did match his mental image of Shizuo was that he was just about as tall as he expected.
In the manga adaptation of The Legend of Zelda: Majora's Mask, a band of soldiers hear of this great swordsman who has the Ocarina of Time and are hoping to beat him, but instead get the child Link. Their leader does warn them about appearances, accepts Link and allows him to train with them, whereupon he trumps them all.
Vampire Game: The reincarnation of the Vampire Lord Duzell is... a kitten. Ishtar does not know what to think at first.
Used in Kirby of the Stars. When the residents of Pop Star learn that a mighty Star Warrior is coming, Tiff pictures a handsome, sword-wielding hero vaguely similar to Roy. Instead, she gets... Kirby.
Used again when the NightMare Enterprises guy that sells Dedede the monsters is seen and turns out to have the same legless, stumpy feet as everybody else, despite looking as if he'd be humanoid and most likely really tall.
In Axis Powers Hetalia, Germany expects Italy to be very sly and powerful as Italy is a descendant of the Roman Empire. Instead, he gets a Lovable Coward hiding in a tomato box, who believes that during wars, the best course of action is to surrender.
Patalliro had this effect on Bancoran when they first met, since the photo Bancoran was given to identify the prince had been touched up to make him look more like a bishounen and less like the chibi he actually is.
In Inazuma Eleven, Fubuki has quite a reputation as a talented athlete, so everybody expected him to be a tall and strong guy. Much to their surprise, he turns out to be the average-sized teen they ran into earlier. Apparently, he gets that a lot.
Fubuki: Oh, are you disappointed after seeing the real thing? Everyone who hears about those rumors assumes I'm a big guy or something...
Used frequently in Ghost Hunt, when people are surprised that Naru is president of SPR at only 17. This is later subverted when they attempt to disguise Naru's identity; Yasuhara (who is really a year or so older) poses as the president, and the client comments, "Yes, I heard you were very young."
In King of Bandit Jing people are often surprised that the titular character is a) the bandit king and b) a rather scrawny looking kid. More so in the anime, for some reason...
Shiffon Fairchild from Freezing may count. One would expect that the unrivaled "Monster" that reigns supreme over all other Pandoras would not be a cute, goofy and good-natured girl who is far kinder than most of those around her.
Bokura no Kiseki is a series that revolves around Reincarnation, so this is bound to pop up. Explicitly mentioned with Ooki, a plain, chubby girl who is the reincarnation of a beautiful female knight. She says she could tell that when she told other characters who she was the reincarnation of, they were visibly disappointed.
Haiyore! Nyarko-san has Mahiro, a fan of the Cthulhu Mythos, remark that he expected Nyarlathotep to look like a giant tentacled beast (or any of the other forms described in Cthulhu lore), rather than a cute teen girl with silver hair and green eyes. Nyarko offers to show Mahiro one of those more horrible forms, but says it'll probably drive him insane, so he declines. The gag is repeated in the second season, except that Nyarko's response is to offer to show Mahiro her "original form" — and start undressing, claiming that it's the form she was in when she was born.
Many people in Attack on Titan are surprised how short and wiry Levi, known as Humanity's Strongest Warrior, is. Considering how fast and precise he needs to be to swing through the air, a bigger and bulkier person would have a harder time.
Rorschach from Watchmen: super strong, intelligent, horrifying scourge of the underworld; also rather short, homely, red-haired and freckled. When he's caught by the police they discover he wears lifts.
Jimmy: I only really saw you in the dark, but look, I even did my hair to look like yours. Hey, what happened to your hair? And your boots, you're not wearing the long boots. I like the long boots better. Johnny: Either my hair burned off in hell, or I sleep-shaved it during a really stupid dream. As for the boots they were hurting my feet. Jimmy: Like I said, I only saw you in the dark, but still, I thought you'd be paler than you are. And you're shorter. I always thought you'd be a bit taller than—
The Hulk's son, Skaar, said this when he first met his father on Earth.
In The Rabbi's Cat 2, when Malka of the Lions says he wants to be admired, his wife tells him he's a legend. Malka replies "So I hear. But every time people see the real thing, they're disappointed."
Happens constantly with Batman. It's not so much that he's not as imposing or impressive as expected, just everyone seems to mention it. Even Tim Drake and Dick Grayson get told this on occasion! It's even funnier after Dick Grayson becomes Batman... he's actually four inches shorter than Bruce Wayne, so for once it's actually accurate.
Set up as a Mythology Gag in the Marvel issue of GI Joe that celebrated the 25th anniversary of the original action figure line by reintroducing the original G.I. Joe, Joseph Colton; when he reveals his identity as the original "Joe" to the current team, one of the newer members, Muskrat, comments "I always thought you guys were... bigger", referencing the original 12" toys compared to the modern 3 3/4" figures.
Charles Fort's response to meeting Nikola Tesla's nuclear-powered atomatic man (aka Atomic Robo) is to remark that he looked taller in the pictures.
The Punisher gets this from time to time (The current Marvel universe stats list him as 6'1" while the MAX version was 6'6"). Not surprising given the legend that surrounds him as "8 feet tall and bulletproof with a million guns and a giant skull for a head" and the fact that most gangsters who see what he really looks like don't live to talk about it.
Subverted in Spider-Men when Miles Morales of Ultimate-verse and Peter Parker of 616 meet: Miles blurts out, during a bout of giddy fanboy babbling, that he was expecting Peter to be shorter. Made especially hilarious by the fact that Miles himself is thirteen and quite frankly tiny.
In the Dark World arc of the Pony POV Series, when Discord meets his little sister Rancor for the first time, she says this about him. He says it's because he slouches.
In "A Change in Plans", the Dursleys wouldn't allow Harry Potter to use the seatbelt, which resulted in him becoming wheelchair bound. Later on, when Harry and Ron first met, Ron refused to believe he was Harry Potter because of this. (Ron wouldn't believe Harry could be a cripple)
The original, of course, is Princess Leia greeting Luke Skywalker with "You're a little short for a stormtrooper."
General Grievous and Anakin Skywalker use this as a back-and-forth insult. Anakin's comeback becomes a bit puzzling since Grievous is in fact far taller than Anakin himself, but then again Anakin is only using it to piss him off.
General Grievous: Anakin Skywalker. I was expecting someone with your reputation to be a bit... older. Anakin: General Grievous. You're shorter than I expected. General Grievous: ... Jedi scum!
Luke Skywalker was somewhat surprised on meeting the great Jedi master Yoda, although that's more "I thought you'd be less senile and less likely to steal my lunch."
In The Film of the BookPrince Caspian, Reepicheep plays the trope for laughs when he and his fellow mice open a door to admit Trumpkin the dwarf into a room of the castle.
Reepicheep: We were expecting someone, you know, taller. Trumpkin:(looking down at him) You're one to talk! Reepicheep: What is that, irony?
Also played by Prince Caspian when meeting the Pevensies, thinking they'd be older. Then again, time goes faster in Narnia, so his expectations were somewhat justified.
Peter: Well if you like, we can come back in a few years.
Braveheart: William Wallace has to deal with this.
William Wallace: Sons of Scotland! I am William Wallace! Young Soldier: William Wallace is seven feet tall! William Wallace: Yes, I've heard. Kills men by the hundreds. And if he were here, he'd consume the English with fireballs from his eyes, and bolts of lightning from his arse.
In Smokey and the Bandit, Sheriff Buford T. Justice is surprised to learn that the police officer he was speaking with over CB radio is a black man, and responds with "You sounded a lot taller on the radio."
In Sunset, Tom Mix tells Wyatt Earp that he's not what he expected, being so cultured. Wyatt Earp replies that Tom's not what he expected either, he then ponders a moment before shrugging and resorting to this trope.
Bill and Ted's Bogus Journey: Bill and Ted have this reaction when they go to heaven to find the greatest scientist in history, and discover that he's basically a Wookie who can split into two Ewoks (or is it two Ewoks who can fuse into a Wookie?). The Grim Reaper tells them, "Did you expect the greatest scientist in history to be from Earth?" which is probably a valid point.
Played with in Idiocracy, where President Camacho tells Joe that he "thought [his] head would be bigger."
Inverted in Inglourious Basterds: the "Jew Hunter" was expecting the Basterd known as the "Little Man" to be shorter.
Collateral: Played straight; When Max, posing as hitman Vincent, meets Vincents "client" Felix for the first time, the latter one plays greets him with the words "I thought you'd be taller". Then again, he'd probably say the same thing to Vincent (played by Tom Cruise), but still.
A Few Good Men: A variation is inverted and then played straight. Earlier in the film, Kaffee makes fun of Downey's aunt Ginny (as Downey is from somewhere rural and is not that bright, Kaffee assumes Aunt Ginny is some kind of hillbilly). When the trial begins, he finally meets Aunt Ginny and is surprised to find she's an attractive, intelligent woman who isn't all that impressed with him.
Kaffee: I'm sorry, it's just... I was expecting someone older. Aunt Ginny: So was I.
The Alamo: After the Final Battle of the 2004 version, when David Crockett has been captured and is offered the chance to beg for his life before General Antonio Lopez de Santa Anna.
Crockett: You San'Tanna? Mexican Interpreter:(nods) Crockett: ... I thought you'd be taller.
Hook: Done retrospectively, and with inverted hero-villain relation:
Peter: I remember you being a lot bigger. Hook: To a ten-year-old, I'm huge.
Inverted in Batman Begins. Mob Boss Carmine Falcone tells a young Bruce Wayne that he's "taller than he looks in the Tabloids."
Played with in The Shadow. Shiwan Khan gets into Lamont Cranston's hidden inner sanctum and immediately says, "I saw you as taller." This may be either a byproduct of Lamont's 'clouding men's minds," or of Shiwan's mental portrait of Ying Ko, Lamont's former self.
In The Neverending Story, when Atreyu is called for his quest the centaur comments that he didn't call for Atreyu the child, he called for Atreyu the warrior. Atreyu explains that they are one and the same.
In Captain America: The First Avenger, during Stan Lee's cameo, he says this exact phrase. Also, when Steve shows up for the supersoldier experiment, everyone in the room stops dead in their tracks and falls silent.
Inverted when Bucky sees Steve for the first time since he shipped out
I thought you were smaller.
In the Eragon movie, two characters, upon meeting Eragon, say, "I was expecting someone more...well, more."
Kung Fu Hustle. The Beast is a legendary killing machine, locked away in an asylum. When Sing is sent to retrieve him, he's a little surprised to see a balding old man, in flip flops.
In Iron Man 1 Pepper, Coulson, and his men enter Sector 16 and find Tony's original suit, mistaking it for Stane's power armor. Pepper remarks, "I thought it'd be bigger". It is!
X-Wing Series: Wedge Antilles and Ysanne Isard had been enemies for years before they finally met. Wedge is an Ace Pilot, so he doesn't need to be big, but... well, he is pretty short. Corran Horn also gets this a lot, being about 5' 4".
In Luke Skywalker and the Shadows of Mindor, Nick Rostu is surprised to find that Luke is Anakin's son; Luke is visibly smaller than Anakin was, about five foot seven to Anakin's pre-suit six foot two. Luke tells him that he takes after his mother.
Arthur from Garth Nix's Keys to the Kingdom books is an asthmatic 12-year-old. By the third book, someone has taken to writing fictionalised versions of his already fairly impressive accomplishments that portray him as seven feet tall and looking akin to a Greek God. People tend to be somewhat disappointed upon meeting him in person.
His sidekick Suzy Turquoise Blue is similarly transformed from a 16th-century English street urchin with historically accurate hygiene to a Ninja assassin killing machine. Dame Primus, the incarnation of the last will and testament of the universe's creator, becomes a were-bear-frog. Ironically, this makes it much less terrifying than it is. Arthur subverts this trope as his constant usage of the Keys causes him to get taller.
Tom Holt's Expecting Someone Taller, unsurprisingly, uses this trope, or at least a variation. When nerdy clerk Malcolm Fisher runs over a badger and wins The Ring of the Nibelung, and with it, rulership of the world, everyone is shocked that such a pathetic wet fish could possibly be the hero of prophecy. The dying badger (who is actually a frost giant in disguise) even drops the title/trope name.
The Chronicles of Narnia: Trumpkin doesn't try to hide his disappointment when he meets the Pevensie siblings in Prince Caspian. Caspian apparently summoned a bunch of children when everyone expected their saviors to be strong, fully-grown warriors... which they were at one time, but Year Inside, Hour Outside is funny that way.
In Grave Peril, when Harry and the Knight of the Cross Michael meet the dragon Ferrovax at a Red Court ball and Michael reveals that he killed the dragon Siriothrax, all Ferrovax deigns to say is "I thought you would be taller".
In Small Favor, Harry has been fighting the Billy Goats Gruff, and each successive set of brothers becomes a hell of a lot taller — with the third wave, consisting of a single gruff nicknamed "Tiny" being about the size of a double-decker bus. Then Eldest Gruff shows up while Harry is hiding inside a building, and Harry levels his staff at the roof of the little shack. He hears Eldest thumping along as he approaches, and aims a little higher. Then, Eldest walks in. He's five feet tall. Five-two, tops.
'I took a slow breath and stepped past her, to face the king of the Red Court. He was kinda little.'
Also played with when he meets Cohen's daughter Conina. The whole town is looking for a mysterious master thief who turns out to be an attractive barbarian woman. Rincewind admits that she is different from what he had expected. It seems like we would get an Aesop about gender equality and not judging people based on looks but instead he just says that she's a bit taller than he imagined.
Played straight when Rincewind meets Coin the Sourcerer in Discworld/Sourcery; Armed with naught but a half-brick in a sock, the wizzard goes up Coin's tower and finds out what the readers have known the entire book- that all-powerful, unmatched Sourcerer is just a little boy.
Big Fido, mysterious head of the short-lived Dog Guild, is a toy poodle.
Taken to the extreme by Miss Butts, the headmistress of the Quirm College for Young Ladies in Soul Music. Her demeanor is so strict, domineering, and pervasive that most people don't realize she's short even when they meet her in person.
In the beginning of Diana Wynne Jones's Year Of The Griffin, the protagonists' University tutor, getting all his pupils to self-introduce themselves, expects Olga Gunnarsson to be the Emperor's sister (because of her regal manner), and the Emperor's sister to be the Wizard Derk's daughter (for her "humble, almost harassed look"). Wizard Derk's daughter actually turns out to be a griffin.
In The Homeward Bounders, an earlier book by Creator/Diana Wynne Jones, Joris constantly talks up his master, Konstam, leading the other characters to picture him as ten feet tall and omni-competent. When he does show up, he's omni-competent but only about five foot six.
In the Doctor WhoEighth Doctor Adventures novel Seeing I, Sam gets a chance to talk up the Doctor to some new friends before they meet him. When they do, he's rather bedraggled and miserable, and only 5'8" anyway, so one of them says that he expected the Doctor to be taller. Sam responds that "he acts tall."
In A Song of Ice and Fire, Prince Oberyn was disappointed (albeit jokingly) that Tyrion (a disfigured dwarf) did not have the spade tail he was rumored to as a child.
Similarly, Tyrion uses this line to great (chilling) effect as a question when privily confronting the final witness at his second trial for murder.
In the Barbara Hambly book Dragonsbane, this is a major component of the surprise that Gareth feels at his first encounter with the titular dragon-slayer, John Aversin — although he is too well-bred to comment.
In Hambly's The Time of the Dark (first book of The Darwath Trilogy), when Rudy sees a young woman being given lots of bossy instructions when she takes the baby heir to the throne out for a bit of air, Rudy assumes the girl is the most junior nursemaid. She's the Queen.
Tortall Universe: In the later quartets, practically everyone has heard of Alanna the Lioness, King's Champion, and her adventurous exploits. Then they find out she's a lot shorter than even most of the other women she works with. No less badass for it, but it makes for some awkward introductions.
"Let me guess. You were expecting someone bigger?"
Mary Renault's historical novels about the Greek hero Theseus pull this trope on the readers, subverting the expectation that Theseus "should" be a towering muscleman with her short, yet quick and agile protagonist. Nicely justified in the author's notes, which point out that a small man would've had far more reason to develop clever fighting tricks, as Theseus is said to have done, than a Big Guy who can win by brute force.
In the Isaac Asimov novel The Robots of Dawn, we learn that the story of the previous investigation of the hero, Elijah Baley, was made into a "hyperwave drama". Consequently, everybody who he meets Baley tells him that he doesn't look like the actor playing him (who was younger and more handsome).
Corum: Michael Moorcock's Corum is a member of a race called the Vadhagh, who are more advanced culturally than humans but, on the scale of the Five Races, fall well within the range of "High Men." He still finds that Vadhagh in general, and Corum personally in particular, are very Shrouded in Myth and are believed to be as powerful as demigods. King Mannach even tells Corum that "I had expected to meet a being at least nine feet tall!"
Also inverted when Corum meets the Sidhe known as Goffanon the Dwarf, who he is expecting to be, well, dwarf-sized, but who turns out to be about eight feet tall. Which makes him a dwarf by Sidhe standards (Goffanon's brother Ilbrec is 16ft tall).
Sword in Attanasio's The Last Legends Of Earth, where the population of a village were expecting him to look more like a Bad Ass and less like a schoolteacher. Then he proceeds to overhaul their defences against monsters, and then kills the biggest monster in the area single-handedly. The moral of this story? Don't judge a book by its cover, wait until the pages have finished beating the shit out of gargantuan freaks of "nature" to make your decision.
Inverted in Agents of Light and Darkness, where a character asks Judas Iscariot what Jesus was really like. "Taller than you'd think" is the reply.
Watership Down: Happens in reverse order, when the Efrafans assume the Watership warren's chief rabbit must be enormous, if the formidable Bigwig follows his orders. They'd actually met Hazel-rah face to face, but took it for granted that he was just a messenger, as he's only average-sized. Justified because most rabbit chieftains attain their position through physical strength, not cunning and charisma as in Hazel's case.
Pulp Western writer J.T. Edson's principal continuing character is Dusty Fog, who though strongly built is only about five feet five inches tall and continually overlooked by strangers who know him only by reputation. Usefully, one of his associates, Mark Counter, really is well over six feet tall with big muscles and the face and figure of a Greek god, and from time to time Mark pretends to be Dusty in order that strangers will blab secrets when he is not around but the insignificant-looking real Dusty is. Word Of God is that Fog was based on Audie Murphy, who was himself of no great size.
Scourge, a Big Bad of the Warrior Cats series. Firestar thinks that Scourge's much bigger deputy is the leader of BloodClan, as he wasn't expecting such a small cat to be leader. When Tigerstar meets Scourge for the first time, he even blurts out, "That's Scourge? He's no bigger than an apprentice!"
In Ranger's Apprentice, everyone who meets Halt, and later Will, is surprised that they're so short, having envisioned a huge, glorious hero.
In the Honor Harrington novel In Enemy Hands, Thomas Theisman thinks this of Cordelia Ransom. He doesn't say it, of course.
In Flashman and the Redskins, Flashy is saved from death at the hands of the Apache by none other than Kit Carson. Carson takes it upon himself to take care of Flashy, travel with him, etc. At one point they're somewhere public when a man comes barging in; he had heard that the great Kit Carson was around and wanted to shake his hand. The small, mild, diffident Carson steps up, while the tall, stalwart Flashy remains in the background. The man can't believe Carson is so small—so Carson gives an almost imperceptible nod to Flashy, at which point the man rushes over and shakes Flashy's hand (and sneers at Carson for trying to fool him). Other Mountain Men hanging around can't stop laughing.
In the Emberverse, after the average-sized Sam Aylward becomes legendary as "Aylward the Archer," he gets this reaction a lot.
In the Anita Blake series, Anita gets this a lot. Her reaction is usually along the lines of "Yeah, it disappoints me too."
The Saga of Hrolf Kraki and Prose Edda relate that Hrolf Kraki of Denmark, the most glorious king of his time, was physically unimpressive. Supposedly he received his epithet when a Swede, Vogg, saw the king for the first time and exclaimed: "I heard say that King Hrolf was the greatest man in the Northlands, but now here sits on the throne a little kraki [a pole ladder], and they call it their king!“ (Prose Edda)
'By the time the last document took its place on the desk Dr Maturin had reached and surpassed the heroic stature expected of him.'
Invoked in Artemis Fowland the Last Guardian. A dwarf realises that he's only seconds away from being murdered by Opal, so he decides to go out with flair by making his last words an insult. "I always thought you'd be taller. Plus your hips are wobbly."
The Lay of Paul Twister opens this way: he meets with a client, who had gone to hire a renowned magical rogue, and at first didn't believe that the teenager standing before him, who'd been pulling legendary heists for years, could be the great Paul Twister. Turns out he just ages slowly.
When Peter meets Mozzie for the first time in episode four of White Collar.
An episode of Star Trek: Voyager called "Live Fast and Prosper" featured a group of aliens who were masquerading as members of the Voyager crew. Janeway got this line from the woman, Dala, who was impersonating her:
Janeway: I have to admit I'm impressed. Dala: I wish I could say the same. The great Captain Janeway. Somehow I expected you to be taller. I make a better you than you. Janeway: Oh I don't know, I'd say we're very much alike. Resourceful, intelligent, ambitious, but with just one tiny difference. Dala: And what is that? Janeway: I'm not a liar and a thief.
In Angel, Illyria reacted along these lines to meeting her priest, Knox:
Illyria: You are the Qwa'ha Xahn. Knox: I am your priest. I am your servant. I am your guide in this world. I've taken your sacraments and placed them close to my heart according to the ancient ways. That's why you were called to me. We're bound together. Illyria:(dismissively) My last Qwa'ha Xahn was taller.
Gen. Hammond: I'm assigning Sam Carter to this mission. O'Neill: I'd prefer to put together my own team, sir. Gen. Hammond: Not on this mission, sorry. Carter's our expert on the Stargate. O'Neill: Where's he transferring form? Carter:She is transferring from the Pentagon. (enters the briefing room) I take you're Colonel O'Neill. Captain Samantha Carter reporting, sir!
Later, when teenage-clone O'Neill meets adult original O'Neill, he comments "Wow. I'm taller than I thought."
Averted in The X-Files when Reyes meets Mulder properly for the first time (he was somewhat dead the first time she saw him).
Reyes: Agent Mulder. Mulder: Agent Reyes? Reyes: You're taller than I thought. Mulder: You keep on alluding to a time that we've met and I don't remember. Reyes: I was there when they found you in the woods. You were... Uh... Yeah. I'm not surprised you don't remember.
General Beckman from Chuck, played by the diminutive Bonita Friedericy. For a while she only appears on video conferences with the heroes, and the first time she shows up in person, Chuck blurts out, "Wow, Beckman is tiny!"
In Father Ted, when Dougal is reminded of once meeting the Pope, he brushes it off as unimportant. Ted reminds him that the Pope is God's representative on Earth, to which Dougal replies "You think he'd be taller."
Sherlock: When the titular character, newly famous, meets an employee of the British government:
Inverted with Canadian TV game show host Jim Perry. He was 6'4", and the set of the game show Definition had a hole for him to stand in, so he wouldn't look so much taller than the contestants.
In one episode of Burn Notice, Michael goes to trade information with a Libyan spy. Mike's name is apparently pretty well known in the Middle East's intelligence community, prompting this line:
Anwar:You're Westen? I thought you would be taller.
In the pilot, a Russian man admits that he (and the rest of the Russian intelligence community) thought that Michael Westen was a code name for a whole team of operatives. "Nope, just me".
Rizzoli & Isles: the team investigates the murderer of an avid MMORPG player, and get a list of his contacts, including one with the name "Grunhilde", whose avatar is a gorgeous blonde Viking and whose real name is Kendra Dee. Frost and Korsak are eager to meet with her...and she turns out to be a mid-60s woman with a romantic streak and a penchant for writing Runic love letters.
In Red Dwarf, Kryten has this reaction to the planet Earth the first time he sees it.
It's exactly like I always imagined, only much shorter.
Inverted in Andromeda, where Dylan Hunt (played by Kevin Sorbo) gets described as: "[...]huge, like a greek god".
Myths & Religion
This trope is Older Than Feudalism. The Jews were expecting Jesus to be this huge, powerful "warrior-king" in the mold of David who would gather up an army and start hacking down Romans in cold blood and stuff. Instead, he turns out to be this kindly, quiet-natured teacher who held some get-togethers, tended to some sick people, died, and (according to rumor) then came back to life after three days. That's part of why there's so much continuity debate between the more classic Jewish fanbase and the revisionist Christians.
The aforementioned King David also had this trope on him: When it came the time for prophet Samuel to anoint the new king, God instructed him to go to a house of a certain Jesse who had many sons. He inspected them, and they were no doubt strong, smart, and reputable, but to the surprise of Jesse and probably Samuel too, none of them were to be the king. Samuel, wondering whether he or God had mistaken the house, asked whether those were really all Jesse's sons. There was one more, a young boy who preferred to spend time alone tending the sheep. Guess which one became the king.
Swedish stand-up comedian Johan Glans once said something about people coming up to him and pointing out that he looks taller on television, and he somewhat sarcastically wondered how you reply to that: "Oh, I'm sorry. I'll shape up, I promise."
Jack Dee (appx 5ft6): "People come up to me and say (sarcastic voice) Oooh, you're not as big as you look on the telly. To which I say "How big's your ***ing telly?!"
Rockville: Done in a subtle but funny way in this mostly-German musical. Brian Carr, dead rockstar turned guardian angel in training, can only be seen by those willing to believe in his existence — initially, only the children and the elderly. At one point, single mom Jackie has to admit that he must exist and talks to him despite still being unable to see him — and keeps looking in the air over his head (prompting the ones who can see him to point at where his face actually is). Brian isn't particularly short, just not very tall, and looks mostly amused.
In the first game, after finishing Chapter 2, people will start mentioning 20-foot-tall heroes in response to the events of that chapter.
In the final chapter, one of the assassins sent after you is an ogre called Larze, who has seen a picture of your face but is otherwise unaware of how you look and act. The player character can use his/hers at that point rather embellished reputation to claim that you're not yourself, since you're not eight feet tall with glowing eyes and a voice that booms as the heavens, causing the ogre to leave to get a better look at the picture.
Done twice in the second game. After starting the Mage Stronghold sidequest, the wizard who teleports in to meet you says that he "thought you'd be taller." Also, when talking to the not-quite leader of the Shadow Thieves guild, he'll say that he " was expecting someone... grander" in response to what he's heard about the PC. CHARNAME can even comment on the fact that he's fairly pleasant for someone with the name "Bloodscalp". There's no option to act offended though, even if you're playing as a halfling.
Jade Empire: The reason your character can walk around freely in the capital even after killing numerous Mooks is that since none of them survived encountering you, nobody knows what you look like and are thus expecting a ten-foot fire-breathing Scourge of the South.
Obviously. Alexstrasza is about twice as big as your player character... in her human form. Dragons in their true forms in the Warcraft universe are usually much, much bigger.
AdventureQuest Worlds uses this trope and lampshades it at the same time in the conclusion of the Vordred storyline, where upon meeting Artix he remarks. 'I always thought you'd be taller...and have a deeper voice.' To which Artix responds 'Yeah I get that a lot.'. This gets repeated when Gravelyn meets Artix for the first time in her ending to the Doomwood saga.
The bonus boss of Touhou 13: Ten Desires is the youkai's trump card against the resurrected saint who served as the Final Boss. The four heroines of the game expected youkai such as the giantskeleton known as a Gashadokuro. Instead, they got Mamizou, a Tanuki. Granted, she's one of the strongest examples of her species and is as powerful as one would expect from a Bonus Boss, but well, as Marisa put it...
Marisa: Aren't you supposed to be the youkai trump card? I figured you'd be amazing, but you're just a tanuki youkai. Mamizou: Oh, I hope you're not making light of tanuki. We have quite a bit of influence in youkai society. You might even call us elite. Marisa: Elite? Mamizou: And in addition, my transformation power is among the top three tanuki of Japan. Marisa: Sure, but you're still a tanuki, right? The kind that drums on their bellies on the night of the full moon, right?
Conker: Aren't you a little short to be a Grim Reaper? Gregg: Well, how many Grim Reapers have you met before, mate? What am I supposed to look like?
In the Suikoden games, this comes up a couple of times. In the first game, some early townspeople will share rumors that Odessa, the leader of La Résistance, is some kind of nine-feet-tall ogre. While Odessa is right there in your party, and completely unnoticed by the townspeople. In the second game, Hoi's impersonating you, but his disguise falls flat when his "True Rune" (actually a bit of body painting) starts to dissolve. Cue one of the villagers admitting that Hoi's actually a little small to be the leader of the anti-Highwind forces. Now consider that Hoi isn't just larger than you, he's pretty hefty. (And that they mistook you for his accomplice...) No way are they going to realize that the genuine article is the genuine article.
In Jade Cocoon 2, after Kahu saves the world from Lilith and the Chosen One of Darkness, he meets Mint, who's surprised by how normal-looking he is, given what he recently achieved.
In Halo 4, Commander Palmer jokingly says she expected the Master Chief to be taller. The Chief is quite a bit taller than she is (depending on the cutscene, she doesn't even come up to the Chief's shoulder). (Canonically, the Master Chief is only 5 inches taller than she is.)
In Tales of the Questor, this is a gag when Quentyn visits a newspaper and meets the artist who drew the front page picture of himself, a raccoonmountain of a Questor. Somehow, having the artist go "Oh poop" at seeing how far off she was is hardly flattering. However, Kestrel, Quentyn's friend, tells him that he might as well appreciate the misapprehension as an advantage to thwart his enemies' expectations.
In Spinnerette, Heather a.k.a. Spinnerette is starting her career as a super-heroine and poses for a newspaper photographer. On the next day, she's very annoyed to discover that they actually photoshopped her taller, because a 5'1 feet tall heroine apparently doesn't strike fear in the hearts of evildoers.
Oswald of Knights-Errant is, well... "really tiny" for a man known as the Behemoth. Or, according to him, everyone else is too damn tall.
In True Villains, it is a running gag when someone meets Sebastian. He never seems to live up to the tales they've heard, including a story of him being six foot three.
Inverted in S.S.D.D with Commander Krutz (a very tall and muscular and, as this is a Furry Comic, fierce looking dog), everyone that sees him and his bodyguard (much shorter than him) always tries to shake the hand fo the bodyguard.
Karin-dou 4koma: The Dreaded Seren has the (temporary) form of a cute child when Meguru and Rindou each meet her, taking them quite off-guard.
Eidolon, in Worm, has this effect when he actually talks to people. Though he is unquestionably the most powerful superhero alive, nobody that talks to him actually likes him as a person, even the heroes that he's worked with for years.
Aang, from Avatar The Last Airbender. Supposedly a 112-year-old master of all elements. He's really a 12-year-old kid who likes penguin sledding. This is commented on by Zuko the first time they come face to face:
Zuko: You're just a child! Aang: Well, you're just a teenager!
In Gummi Bears, when Cubbi became the superhero the Crimson Avenger, the rumors get so out of hand that he is thought to be a tall human. This helps keep the existence of the Gummi Bears secret.
In the Disney animated holiday special, Mickey's Christmas Carol, the Ghost of Christmas Past is played by Jiminy Cricket. When he introduces himself to a bemused Uncle Scrooge, Scrooge replies, "Ohh. I thought you'd be taller."
Total Drama Island: In the first episode Beth runs up to Chris, the host of the show, and hugs him; after letting go she comments, "Wow, you're much shorter in real life."
Pound Puppies (2010): In one episode, the dogs are being visited by a legendary puppy rescuer known only as The General. When The General actually arrives, they're all surprised to find that she's a fluffy pink poodlewith a southern drawl whose reputation seems to come from the fact that male dogs fall all over themselves to do what she asks.
In Wakfu season 2 episode 6, a trio of Sadida children comments that they were expecting someone taller about the red-headed warrior — i.e. the resurrected Sadlygrove.
Jesus: Okay, everybody, uh, I know you were expecting something else, but as science will tell you, people were a lot shorter 2,000 years ago.
In a Winnie the Pooh Christmas special, Pooh fears he has made it impossible for the letter he and his friends wrote for Santa Claus to reach him, so he disguises himself as Santa in an attempt to rectify his mistake and get his friends the presents they wished for. Unlike Santa, Pooh isn't very stealthy, Tigger, Rabbit and Eeyore each notice him coming into their houses and each comment on how they thought Santa would be taller. Of course, this is Justified as Pooh is obviously not the real Santa and, being a teddy bear, can't be more than a foot or so tall.
Daemon: (gently) Yes. Did you expect something else?
Mike: Oh, actually... yes. I mean, where are the talons and the teeth and the spiky things? You're a little small for a supervirus, aren't you?
Hiccup gets this in Dragons: Riders of Berk when Alvin The Treacherous couldn't believe that the famous "Dragon Conquerer" was 'Stoick's little embarrasment'; a scrawny little boy with a fake leg.
Real life example: Composer John Mackey is a lot shorter in person than you'd think. Considering how famous he is in the orchestra industry, you'd expect someone to be a little taller.
It's common for porn stars, especially male ones, to be shorter than they appear on film/video or are advertised as being. This is because the same attribute (or attributes) will appear proportionately larger on a smaller person without an obvious frame of reference. Also, pairing a man, however tall, with a woman shorter than him will make him seem... taller in comparison to her.
If a Hollywood actor is short, camera magic can make them taller. By shooting only head on or from below, or by pairing them with shorter costars, they will seem taller.
In The Year of Living Dangerously, the 5'9" tall Mel Gibson appears to be taller than the 6'0" tall Sigourney Weaver. This was accomplished through the use of camera angles, movable platforms, shoe lifts, and once even putting Sigourney Weaver in a shallow hole in the ground.
It was common to make doors to Old West saloons smaller to make cowboy actors look bigger.
Tom Cruise kind of zig-zags this trope. He's 5'7", which is just a little below an average man's height in the US. But a combination of being briefly married to 6'0" tall Nicole Kidman and becoming the butt of jokes due to his actions during interviews led to a barrage of jokes about his height, to the point that many of his detractors assume he's even shorter than he really is. All of this doesn't change the fact that he's still shorter than many of his costars.
Jon Stewart often jokes about getting this reaction from fans in his studio audience. Jon is known to poke fun at his own lack of height whenever he interviews a tall guest.
A great many fictional stories have someone meet the president of the United States or some other important leader and find him shorter then expected. Although it might not be likely in Real Life much, since the last average-sized president was the 5'9" Harry S Truman (Jimmy Carter as well; he's a half-inch taller than Truman was).
May not always be Truth in Television in the US, but it certainly is in the rest of the world. Before Obama was elected, Canadian PM Stephen Harper was the only G8 leader taller than 6'0".
Many people in the USA believe that height confers a substantial advantage in presidential elections (Reference), to the point that in televised debates, organizers and TV networks go out of their way to avoid making one look more attractive than the other for superficial reasons. Watch a clip from the 2004 or 2008 debates, both of which had candidates with significant height differences; on the split screen, the candidates' eyes are on a level with each other, but the podium looks noticeably higher on one candidate than on the other.
Yet in three out of the last four US presidential elections, the shorter candidate won. George W. Bush (5'11") defeated Al Gore (6'2") and John Kerry (6'4"), and Barack Obama (6'1") defeated Mitt Romney (6'2"). The trope held true, though, when Obama defeated John McCain (5'7").note Bill Clinton is also a very tall man, 6'2", but both the Republicans he defeated – George HW Bush and Bob Dole – are about the same height as he is, so the analogy doesn't really apply there either. It did, however, apply to the elder Bush, who had a six-inch height edge over Michael Dukakis.
Audie Murphy was a small man despite earning so many military decorations that it's quite the feat of memory to list them all. In fact, his height and build almost relegated him to being a cook before his persistence got him a frontline post!
Iron Chef Masaharu Morimoto is about 5'3". You'd never know it from watching the show, since they shoot the Iron Chef intro from a low angle.
Inverted with Ryan Stiles. He just seemed shorter than he really is because most of the other actors he worked with were also relatively tall.
The queen of a defeated Persian king once addressed Alexander the Great's friend Hephaestion as Alexander because he was both taller and more handsome. When the mistake was pointed out to her, she tried to apologize, but Alexander said, "Worry not, Mother – he too is Alexander."
In the reality TV show I Get That A Lot where famous persons pretend to be ordinary citizens who just happen to look like a famous person, the late Larry Hagman was on and someone told him he wasn't "Larry Hagman" because the real Larry Hagman was taller.
In the introduction to Dangerous Visions, Isaac Asimov and Harlan Ellison recount their first meeting, when young fan Ellison walked up to the elder author and said, "I think you're (beat) nothing." Ellison was invoking this trope, although Asimov initially took it as something more insulting.
The Reverend Billy Graham once told a story of how he was in a hotel for a conference. He was in an elevator along with his associates and businessmen who were also staying in the hotel. One of the businessmen turned to another and said, "I heard Billy Graham is staying here". The men in the elevator smiled and pointed Graham out to him. The businessman sized him up and said "What an anticlimax". Graham chuckled and said, "I'm sorry, this is all there is."
An actress being short is usually less of a problem than an actor being short (as mentioned above), since we generally expect women to be shorter than men. However, if an actress is very short, (and especially if not only her male co-stars but also the female ones are considerably taller), her character often ends up wearing ridiculously high-heeled shoes in every scene to make the height difference look less dramatic.
Holland Roden's (5'3") character on Teen Wolf, Lydia, almost always wears extremely high heels, making her look almost as tall as her best friend Allison (played by Crystal Reed, who is 5'8").
On Elementary, Watson (played by Lucy Liu, who is also 5'3"), keeps wearing extremely high-heeled shoes even when it would make more sense for her to be wearing more comfortable shoes or even no shoes at all.