Used as a Running Gag throughout Cars 3 with Lightning McQueen, who at the time of the film, is now a 7-time Piston Cup racing legend. Characters often say he's old, which offends him, despite the fact he still looks pretty young since day one, even having the same young voice. On top of that, Smokey and the Thomasville Legends are among those who tease him, yet they are much older than he is.
In Epic given Queen Tara's held her position for a century, both she and Ronin (on account of being childhood friends) look very good for beings which have not only lived a century but, due to their heightened speed, must actually experience that period of time as being at least twice as long as it is for humans.
Finding Nemo: Crush said it best himself: "150, dude, and still young!"
A cut scene from Madagascar revealed that Ridiculously Cute Critter Mort, who behaves and, at least to human eyes, looks like a toddler, is actually 35. Justified in the looks arena because he's a mouse lemur, which are all small, fuzzy, and big-eyed. No excuse for his childlike behaviour beyond Rule of Funny. Eventually made explicit in an episode of All Hail King Julien when Mort pretends to be Julien's son and the primary objection people have to this is that Mort is older than Julien; a later episode implies he is at least in his 50s.
The twins in 9 look and behave like the youngest members of the group, but with the Numerical Theme Naming their names (3 and 4) would imply that they're younger only than 1 or 2, each of which have their apparent ages made a point.
Baby Herman from Who Framed Roger Rabbit looks like a toddler, but off-camera acts more like a gruff, cynical, womanizing middle-aged man. As he puts it to Eddy, "I got a 50-year-old lust and a 3-year-old dinky."
Charles Muntz of Up is well into his nineties, but doesn't look any older or any less in shape than Carl, who's younger than him by two decades.
Implied with Tigress. Po wonders if she's in her twenties in the cartoon, but it's implied she's in her forties.
Lord Shen in Kung Fu Panda 2 appears to be in his early twenties, but the fact that he was exiled for over twenty years and looked the same then would put him in his fifties.
Zootopia has Finnick, Nick's partner in crime, who looks like a fox cub but is actually an adult. He's the size of an infant because he's a fennec fox, a very small species of fox.
The pairing of Steve Carell and his twenty-years-younger costar Anne Hathaway in the movie Get Smart might have made the romantic subplot a bit icky, if not for Hathaway's character explaining that the Magic Plastic Surgery that completely altered looks also took years off her apparent age and that she was in fact not much younger than him. As a plot point, it also serves to explain their pairing (99's plastic surgery and Smart's lack of experience made them the only two agents KAOS didn't know after Control was compromised.)
The midgets Hans and Frieda in Freaks. As Hans explains to Cleopatra in one scene, he resents people who don't understand that although he appears to be a child, he is in fact a man.
In Inception, Both Cobb and Mal were in Limbo for around 50 years, making them mentally in their late 70s to early 80s. Saito too. And, depending on how long Cobb was in Limbo hunting him, he may be north of a hundred by now.
Austin Powers was frozen in the 1960s, and had to have been in his late 20's. He was frozen for 30 years, and would be in his early 60s by 2002. His dad Nigel appeared about the age Austin would be, had he not been frozen.
The case with Doctor Evil is a little more confusing. He looks quite a lot older than Austin and at one point claims to be his father, but they were roommates at school and are later revealed to be long-lost twins.
The Curious Case of Benjamin Button. As a man who ages in reverse, in the latter half of his life, he always looks younger than he actually is. As an old man, he suffers from dementia and Alzheimer's, but he has the body of a child and eventually degenerates into infancy, at which point he dies, his version of death at old age.
In the controversial horror film Orphan, the titular character is a psychotic 33-year-old serial killer suffering from a hormonal disorder which keeps her stuck in the body of a young girl. Her M.O. is posing as a young orphan girl, who ends up killing the families who adopt her.
In Star Wars Episode I, Qui-Gon Jinn was sixty years old when he encountered Anakin.
Yoda teases Luke about it in Episode VI. Other members of his species (such as Master Yaddle, or Master Vandar Tokare) were confirmed to be younger than him, and they looked as old, if not slightly older than him.
"When 900 years old you reach, look this good you will not, hmm?"
Han: Since when do you know how to fly? Chewie:*growls* Han: You're a hundred and ninety years old? Chewie:*growls* Han: You look great!
Near Dark: "You have any idea what it's like to be a big man on the inside and have a small body on the outside?"
In Swedish vampire movie Let the Right One In, the vampire appears to be a young girl. Asked by the protagonist how old she is, she says "I'm twelve.... but I've been twelve for a long time." The movie never does reveal exactly how long...
In Airheads, 36-year-old Steve Buscemi plays a twenty-something heavy metal guitarist, and ends up looking more authentic than twenty-somethings Brendan Fraser and Adam Sandler. Let's just say metal fans aren't really known for taking care of themselves.
While Christopher Mintz, as well as his character in Superbad looks appropriately like a high school student, this trope happens as an in-movie example as the liquor shop clerk implicitly assumes that her 25-year-old customer is simply older than he looks.
Wolverine. All because of his Super Healing Factor. He was born in 1823, but as of today, he still physically appears to be a buff as hell mid-to-late 30s. His powers constantly rejuvenate his cellular integrity rendering him seemingly ageless. He's not by any means immortal, he just ages at an incredibly slow rate, if at all.
Since X-Men: First Class is in the same continuity as the original films, Mystique would also qualify an another extreme example, being played by Rebecca Romijn despite being only a few years younger than Magento and Xavier. Justified by her ability to shapeshift (why age if you never have to?) and a comment made in First Class about her mutation slowing her aging.
Sebastian Shaw looks to be in his late forties or early fifties when Erik first meets him in 1944. He looks more or less the same when they meet again in 1962, a fact that he credits to his Energy Absorption powers.
Done retroactively with Moira McTaggart. In X-Men: First Class she is shown as almost the same age as Charles Xavier, but in the original X-Men trilogy Charles was played by Patrick Stewart whereas the lovely Olivia Williams played the modern-day Moira in X-Men: The Last Stand. Stewart is 30 years older than Williams.
Given the reveal in X-Men: Days of Future Past that Toad was a soldier in Vietnam, he was somewhere in his forties during X-Men. Ray Park was only 26 at the time.
Charles, Erik, Hank and Alex Summers all physically look pretty much the same as they did in X-Men: First Class, despite the fact that it's been over a decade since the events of that film. (Mystique is excused, since her mutation slows her aging process.)
Despite being twenty years older, everyone looks roughly the same. Even odder, Alex Summers' younger brother Scott is still in high school, making him young enough to be his son.
Lampshaded by Charles who says Moira hasn't aged a day.
Logan: Downplayed somewhat — Laura is 11 years old, but you'd easily be forgiven for thinking she's even younger. She's positively tiny, and much of her behavior and mannerisms are much more appropriate for a child half her age.
In a scene from the Director's Cut of The Two Towers, Eowyn was startled to realize that Aragorn was over eighty years old. This is because he's a Dunedain, who have a bit of elven blood in them.
Dr. Lao in Seven Faces of Dr. Lao confesses to being 7,322 years old!
Kruger from Elysium. According to supplementary material, he was born in 1970, making him almost 200. This is also implied with Delacourt and the other members of Elysium's elite. It's one of the theories regarding why Immortality Immorality pops up: you let one generation live too long in power, they're going to get really corrupt and ego-maniacal.
In Another Time, Another Place this may overlap with Dawson Casting, since Janie's age is never actually clarified. She looks about 19 or 20 at a push, and even younger in certain lights. Phyllis Logan was actually 27 at the time the film was made, so she could be anywhere between 18 and 30.
In Robinson Crusoe on Mars, when the stranded Commander Draper finally gets the second black bracelet off of Friday, he asks how long he had it on. Friday replies "Sixty-two years". He they explains he's seventy-eight (although it's unclear how long he considers a year). For the record, the actor who played him (Victor Lundin) was 34 when the movie was released.
Rapunzel in Into the Woods. She should be the Baker's sister, meaning she'd have to be around his age. She doesn't look it at all. Possibly justified in-universe because she has mostly avoided sun exposure for her whole life. And the issue also exists in the source material, when the Witch says she took Rapunzel when the Baker was "no more than a babe" and Rapunzel states she was locked in the tower for 14 years, which should make the Baker a teenager.
Appears to be inferred in Iron Man 3. Dr. Maya Hansen is played by Rebecca Hall both in 2012 scenes and in a flashback set in December 1999. She's either supposed to be a Teen Genius or she's a few years older than Hall (since Hall was born in 1982 and would have been 17 years old in 1999).
In The Asylum's version of Sleeping Beauty, Dawn comments jokingly that she was "very young" on the day of her christening. When Barrow says that Dawn is still young, she points out that due to the time she spent sleeping, she is now over a hundred years old.
Clara from The Light in the Piazza is twenty-six but looks like she could be in her late teens or early twenties. She acts even younger than a teenager due to a mental disability.
Odd Squad: The Movie reveals that Ms. O, despite looking like a child, was actually around back in 1983.
The plot twist/"long con" in Matchstick Men. His 14-year-old "daughter" Angela is a friend of his business partner. The young woman is played by petite blonde Alison Lohman, who is very convincing in the part. She was 22 at the time of filming.
Roy: You look grown up.
Angela I am a grown up.
Harry Potter: Albus Dumbledore (at least Michael Gambon's version; Richard Harris looked more convincing) looks to be around 65-70 years old but is actually 116 as of his death.
In the Soviet comedy film The Boys from Leningrad, the main protagonist, Vasya Vesnushkin, is 18 years old, while Vasya's actor, Georgy Vitsin, was 37 years old!
Played with in Dune with Paul's sister, Alia. She's really only a toddler both physically and mentally, but is imbued with all the knowledge and psychic powers of an adult "Reverend Mother" and so often behaves in a way which implies this trope, despite it not being literally true.
Cid, the young version of The Rainmaker, a mob boss with telekinetic abilities from the past in Looper, is stated to be 10 years old, however he looks and acts as if he were 7 or younger. The actor who played him actually was around seven at the time of filming.
Mythica: Dagen (a half-elf), says he's in his early seventies, but looks perhaps thirty at most. It's possible he's joking though.