In general, anyone who is well below average height can fall under this trope. From the examples below, Frankie Muniz is 5'4" (where the average male height is 5'9"), and Senta Moses is 4'11" (average female height is 5'4"). However, below about 5'2" or so, there is a tendency for actors and actresses to look older than their real age, as they seem like adults the size of young children (or else suggest Miniature Senior Citizens). Danny DeVito (5'0") is a good example of this, having looked to be in his 50s since his mid-30s (when he was working on Taxi). In cases of dwarfism (e.g., Verne Troyer, 2'7", born 1969), the effects of the condition itself can also cause premature aging.
Despite the effects of Parkinson's disease, Michael J. Fox (5'4") still looks to be in his early twenties much of the time. He was born in 1961.
Not despite, because of: people with Parkinson's often look younger than they are because of the buttociated paucity of expression.
A similar effect happens with those with Down syndrome. This, coupled with the tendency for such patients to die young, makes their real ages hard to determine. Ex: Chris Burke was 22 when he played 16-year-old Corky Thatcher in Life Goes On, the first series to have a major character with Down syndrome. He's nearly 50 now, but he still doesn't look it.
Some autistic people are usually legitimately thought to be younger than they actually are, even if the onlooker does not know that they are autistic, strangely enough. This phenomenon has been attributed to many autistics just not emoting much with their faces, so they tend to develop fewer wrinkles. The equally common wide-eyed expression (or "the autistic stare") many autistics have might also make them seem childlike.
Neoteny is an evolutionary process whereby an organism retains once exclusively juvenile traits into adulthood. Humans have this trait. We grow up more slowly than other apes, and spend more time in the learning-conducive childhood stage. As adults, we remain childlike by ape standards, with high foreheads, flat faces, and less powerful physiques.
Some people of Asian descent frequently appear younger than they actually are for several reasons. Asians tend to be shorter than people of other ethnicities, which, as noted above, contributes to a more youthful appearance.
People of African descent often look relatively young for their ages as well. This can be attributed to melanin offering some protection against wrinkles, as well as wrinkles often being less noticeable on darker-skinned people. Furthermore, black people tend to develop gray hair a bit later than other ethnicities due to melanin.
Most of the cast of A.N.T. Farm are subject to major Dawson Casting, including the main cast. That said, they still look like the ages their roles are supposed to represent, typically at least two years younger than the performers' actual ages.
Jake Short (Fletcher) is the most extreme example; he looks 12 at most despite being 16.
In general, people who are more weighty tend to look younger than their thinner same-aged counterparts, because the "face puffing" that happens when one puts on a lot of weight can hide or stretch out wrinkles and age spots.
Men that lack facial hair, whether it's due to shaving or not having any facial hair to begin with, tend to look younger than they really are.
Similarly, for both men and women, styling/grooming your hair in a certain way can make you look younger and other styles can have the opposite effect.
Due to advances in plastic surgery and make-up techniques, as well as the nature of their jobs, most celebrities tend to deliberately look younger than what they really are. Coupled with the fact that most publications use editing to enhance the looks of celebrities in their covers (see the Specific People folders below).
To keep this list organized, please add examples alphabetically by their surname. Do not add combined examples (listing more than one person simultaneously). Additionally, a link to a recent picture of the person is advisable, along with their actual age and perceived age, so that it gets the point across.
Danneel Ackles (formerly Danneel Harris) was 26 when she signed on to play 16-year old Rachel Gatina on One Tree Hill, but you never would've guessed just by looking at her, even now in her 30s, she looks barely out of high school.
The French actress Isabelle Adjani. She was born in 1955! This is particularily striking in La Reine Margot, where she plays a 19-year old princess pretty darn convincingly. Despite being 39.
Casey Affleck is now 38 but looks about ten years younger. This is usually lampshaded in roles where he is acting alongside actors who are older and look it.
Keiko Agena was 27 years old when she signed on to play the 16-year old Lane Kim on Gilmore Girls (only six years younger than co-star Lauren Graham), and many fans couldn't believe it even when they learned her real age. In this case, the Dawson Casting worked out fantastically.
Freema Agyeman. She looks like she's in her early-to-mid twenties on Law & Order: UK (her character has been working for the Crown Prosecution Service for about two years after law school - which she'd have completed at about 22 or 23 - as of series 4), despite the fact that she was 30 when the series premiered.
Also Jessica Alba, who looks almost exactly the same today as she did when she debuted in the late '90s. She blossomed early and maintained it all the way today, as she admitted that she already had "womanly curves" at a young age. Regrettably, the downside of this is that this is likely the reason for her complaint that she can't get the more serious roles that she really wants to have. Luckily, the upside of this is that helps keep her in-demand as a product endorser.
Damon Albarn from Blur\Gorillaz. In his late twenties he still could have easily passed for a 20-21 years old, and even today he looks at least ten years younger than his age.
Scott "Klayton" Albert, the man behind the metal/electronic project Celldweller, looks like he's in his late 20's/early 30's. He was born in 1963. Some people have denied this fact, but it's the most common birthdate shown online, plus his first project was in 1992 so it's unlikely he was a kid back then, so most people just go with it.
Jyoti Amge, 16, is the world's smallest girl. She is 1'11" or about the size of a 6 month old baby.
Shiri Appleby (of Roswell) is 34 years old as of 2013, and has been convincingly been playing teenagers for over fifteen years. Even though she played a grown woman and mother of the main character on Life Unexpected, she still looked like a teenager!
Asia Argento is 38, but looks to be about ten years younger than that. Of course, she is Italian.
Rowan Atkinson will be 59 in January 2014, but could still pass for early-to-mid forties.
One might argue that this is a bit of a subversion though: Just having a look at his classic Mr. Bean skits, which he did when he was in his thirties, he could've passed for someone in his mid-forties even back then. He sure hasn't aged much SINCE then, though.
Adam Baldwin. Did you realize that he's 51? That means he was 40 during Firefly. How many people really look like this◊ at forty?
Jamie Bamber is another one of these. He was 25 years old when he did the first Horatio Hornblower films but passed for a very convincing seventeen. This continued when he went on to work on Battlestar Galactica - he was 30 years old to Katee Sackhoff's 23, but they looked the same age (especially since Katee was playing a character a couple of years older than her actual age). Even now at 40 (which in and of itself is still relatively young), he can convincingly pass for someone in his mid-thirties rather than 40.
Hard rock singer Alex Band of The Calling practically defines this trope. Look at this picture as carefully as you possibly can.◊ Good. Now try to guess how old he is. Check◊ these◊ out◊ if you still aren't sure yet. Most of you are probably going to guess that he's around 15-17. That couldn't be further from the truth. He's THIRTY-TWO!! I'm not lying. THIRTY-TWO!! It's kind of ironic though, because his voice is extremely old and deep for his appearance. Picture this: Jesse McCartney when he was young with the voice of Scott Stapp from Creed except even lower.
Paul Banks of Interpol looks like he's in his early or mid 20s. He's 35.
Anita Barone is 49 but due to having a hot body, she can pull off playing Georgia Jones, the mother of Bella Thorne on Shake It Up ,who is around her mid-to-late thirties.
Dave Barry looks maybe in his 40s at the oldest◊. He's 66. This was apparently a longtime issue with him, as he once told People magazine, "I reached puberty at 30. At 12, I looked like a fetus."
Ditto for Drew Barrymore, who in her mid-twenties, was still able to pass◊ as someone in her mid-teens. She'll hit 40 in February 2015.
Actor Dante Basco is currently 36 but he doesn't look like he aged much at all since his role as Rufio in Hook and he was 16 back then, and today he still plays and voices teenage roles.
Shirley Bassey was born in 1937. And looks 50-ish. Heck, she looks younger than people born after her first hit (The Banana Boat song in 1957)
Kathryn Bigelow is 61 (Kathryn was 58 when she won her Oscar) but could easily pass for a 30-something.
Selma Blair of Hellboy fame is 41 but still looks mid-to late twenties.
Alexis Bledel of Gilmore Girls is 32 as of 2013 but looks barely out high school for many years. She was on Conan recently telling him how she actually has to wear makeup to look older when she goes out and that a teenage boy hit on her when she was at the airport!
BRIAN BLESSED is already in his late 70s but looks decades younger.
David Bowie is now 66... he just escapes the aging process.
Terry Bozzio◊ (on the right), longtime drummer for Frank Zappa and co-founder of Missing Persons, is 61 — ten years older than the also pictured John Stannard, president of Hammerax. This picture doesn't really do him justice, though - he must be seen in action.
Rose Byrne is 32 but still looks to be in her 20's.
Actress Dyan Cannon is 75 but she looks to be in her late 30's - early 40's, apparently she's had a lot of plastic surgery.
Mariah Carey is 43 but looks like she's in her early-30's at most.
Recently retired NFL official Mike Carey (who was named the rules expert for CBS' newly acquired Thursday night NFL coverage) did not look anything like an official in his 60s; as this exchange with Brett Favre showed:
Brett Favre: I'm probably older than you. (Mike Carey grins) Close? (Carey grins) How old are you?
James Caviezel, well into his 40s, looks like he's in his late 20s.
Japanese pro wrestler Cherry (no, not the one that was in WWE) had a gimmick where, when questioned about her age, would claim she was "Forever 18". However she recently lost a match where she would be forced to show her passport and thus reveal her true age: turns out she was born on May 14, 1974... 37 going on 38! Twenty years older than what she was billed at yet looking far, FAR closer to her gimmick age.
Gary Coleman had an autoimmune kidney disease, which, combined with the medications used to treat it, limited his growth to 4 ft 8 in, and his face retained a childlike appearance well into adulthood.
Monique Coleman (Taylor of High School Musical) is in her early thirties as of 2011. She got away with playing a teenager while in her mid/late twenties. It didn't help that she was the oldest of the main cast.
Sean Connery is a subversion, because yeah, he does look old, no denying that, but he simply hasn't changed a bit from the day they shot Indiana Jones and the Last Crusade...and it was twenty-three years ago! See for yourself◊. Of course, that might not be the best reference point to use, since the production crew went to great lengths to make him look older than he actually was - at 58, he was 17 years younger than the character's implied age, and only 12 years older than Harrison Ford.
Tom Cruise is 51 but could easily pass for a man of about 35.
Benedict Cumberbatch is 36, but can still easily pass for mid-twenties. He is so ethereal and unusual looking that he skews any attempt to classify his age in comparison to more normal appearances. During the UK premiere of War Horse, he asked how old a reporter was because he thought he was about his age. The reporter replied that he was 27, and said Cumberbatch looked even younger than he did.
Singer and actress/voice actress Elizabeth Daily is 50 but she looks like she's in her late 20's-early 30's.
Matt Damon and Josh Brolin are in their early 40s but anybody who saw them in The Coen Brothers' True Grit (or anything else for that matter) could be forgiven for thinking they're about ten-fifteen years younger.
Vin Diesel is in his mid-40s but looks at least a decade younger (his bald look certainly helps), especially noticeable in the Fast And Furious films, his co-star Paul Walker noticeably ages(but still looks pretty good mind you) whereas Vin looks almost exactly the same in the fourth and fifth films as he did in the first one.
Khanh Doan, age 35, looks late teen-ish. Then again, she's Asian.
Nina Dobrev is 24, but could easily pass for a 16-18 teenager.
Declan Donnelly once revealed in a magazine interview that he was commonly mistaken for being underage by bartenders while in his mid to late twenties. He's now 34 and the effect is less pronounced, but he still looks quite young for his age.
Robert Downey, Jr. looks surprisingly good for his age, given his years of drug abuse and rough living. In Iron Man, he's in his mid forties and could pass for about ten years younger. This is especially odd as he was in Kiss Kiss Bang Bang a few years prior and looked like he was pushing forty.
Jason Earles, aka Jackson, is in his 30s and married. He even mentioned on Late Night with Jimmy Fallon, that when he takes his wife to dinner fans of the show would go to his wife and say "You must be so proud of your son". Awkward! In the first season of Hannah Montana, he was 29, playing a 15-year old character who looked that age. In The movie "Dadnapped" he looks ridiculous trying to play a character who is likely his own age named Merv . Plus coupled with the fact that the primary audience for this movie are people who know him as Jackson from "Hannah Montana" makes it even less believable"
To really drive the point home, watch this guest appearance by John Cena on Hannah Montana. As you're watching it, let it sink in that they're both the same age!
Barbara Eden: During her visit to Vienna in late May 2013, she briefly put on her iconic harem costume. She still looks gorgeous at 78.
Zac Efron (from High School Musical) is in his 20s, but looks teenage. He said it best in his monologue to his tween girl fans on Saturday Night Live: "If it weren't for you, I'd be some random college student, instead of a college-aged man pretending to be a high schooler." And when he was 14, playing young Simon in a flashback on Firefly (yes, that's him), he looked like he was about 12.
Josh Elmore is in his late thirties, but looks like he's in his early to mid-twenties.
Michael Emerson was born in 1954 but looks like he's in his early 40s at the most. He was already 51 when he started playing Ben on LOST, but doesn't look a day older than the rest of the cast who are about 10 to 15 years younger. Especially impressive in his scenes with Evangeline Lilly. He looks at most a few years older but is actually twenty-five years older than her.
Actor Robert Englund, famous for playing horror icon Freddy Krueger, is currently 66. Look at this picture.◊ That is him now. He looks like he's in his early-to-mid-40's at least, and early 50's at most.
Lead singer of Mindless Self Indulgence, Jimmy Urine (actual name James Euringer) looks like he's at least in his early-to-mid 20's, but he's actually in his 40's. Doesn't stop the fact that he has a massive amount of fangirls.
Anna Faris is in her mid-30s, but she looks at least 10 years younger.
Terry Farrell. She◊ is almost fifty! (Bonus points to her for aging so gracefully that she doesn't even deem it necessary to dye her hair. Grey streaks? – Who cares!)
Until very recently, original Ultravox lead singer John Foxx did not look his age. In this video, he's all of 33 (since the single was released in 1980 and he was born in 1947), and in this 1998 VH1 Europe interview he certainly doesn't look fifty-one.
Though you hear his voice more than you see his face, voice actor Crispin Freeman totally qualifies. He's 39 as of this writing but looks like he's early- to mid-twenties... just one of many reasons the fangirls love him.
According to Freeman himself, this is actually why he moved on to voice acting from theater: his voice and appearance are mismatched, limiting the roles he could take on stage.
There's an entire genre of international porn based on barely-legal girls who appear illegally underage. Obviously, this can get people into messy legal trouble. Columbian-born Lupe Fuentes gained international notoriety when her porn videos very nearly got a Puerto Rican man sentenced to 20 years for possessing child porn. What made the case notable was that it absolutely embarrassed the over-zealous prosecutor who, despite easily available proof online and on-file with the US Federal Government that Lupe Fuentes was indeed already of age, she stubbornly insisted that the actress couldn't possibly be older than 13-14, based on the sworn testimony of several expert witnesses who relied on the Tanner Scale. The defendant was overruled in the presentation of proof-of-age evidence and was only saved when Lupe Fuentes actually travelled from her then-residence in Colombia to personally appear in court with documentation to prove that she was indeed already 19 years old when said videos were made.
Everybody remembers Harrison Ford as Han Solo... or at least, most females do. He was nearly forty during Star Wars.
Jason David Frank was 29 during the filming of Power Rangers Dino Thunder, but he didn't look like he aged too much since his previous seasons as Tommy and he was in his early twenties back then (well, 19 as the Green Ranger). This was pointed out in the first episode when Cassidy asked if Tommy was really old enough to be a teacher. He responds by saying, 'I can assure you, I'm old enough.'
Edward Furlong was 14 years old playing 10-year old John Connor in Terminator, and 21 playing a 16-year old in American History X. Even in his 30's he still has quite a youthful demeanor and high-pitched voice.
Neil Gaiman is 52 but looks like he is in his mid-forties at the most.
John Gallagher is in his early forties, yet still looks more or less the same as he did back around 2000.
Jennie Garth is 41 but looks young for her age. Dress her up as her 90210 character Kelly and she'd still look like a teenager. Ironically, she was one of the few 90210 actors that actually were teens when the show began.
When Bill Gates was around his twenties, he was often mistaken for being a teen. Even today, he's 58 but could still pass for early-to-mid 40's.
Brian Geraghty is 38 yet can easily pass as early 20's, and is often cast as the rookie soldier in movies like The Hurt Locker or Jarhead, and most recently Boardwalk Empire though there his seeming youth is intentional and pretends to be a rookie cop while in fact being on first-name basis with Edgar J. Hoover and having been in military intelligence during WW1.
Sarah Michelle Gellar was 19, nearly 20 in fact, when Buffy the Vampire Slayer premiered. She was baby-faced enough to look astonishingly convincing as a 16-year-old. She's now 35, and has only just begun looking like she's not a twentysomething.]
Summer Glau is another Whedon favourite whose small size, slender build, and delicate, childish features let her convincingly play characters who are supposed to be a good ten years younger than her actual age. Here's◊ a picture of her from November 2012; she's 31 years old and still looks like she's in her late teens or early twenties. In The R. Tam Sessions, a then-23-year-old Summer managed to convincingly play a 14-year old girl.
Joshua Gomez, best known for playing Morgan Grimes in Chuck, is 36 years old, but looks like he is in his mid 20's. Here's Proof.◊
Selena Gomez, which can lead to some Squick-ish tendencies as this◊ cover for Another Cinderella Story shows (Selena is 15 at this time, her love interest is played by a 25-year old, and Selena looks younger than she is.)
Kim Gordon of Sonic Youth is 60, but looks far younger. The picture on the link was taken when she was 59. 
Lucas Grabeel, the guy who played Ryan Evans on High School Musical. He's in his late twenties (about 27 or 28), but pictures make him look about half that age. See for yourself.◊
Brooke Greenberg has an unknown medical condition that prevents her from aging. She was really 20 years old when she died, but she still possessed the body of an infant and the mental capacity of a toddler.
Radiohead's lead guitarist, Jonny Greenwood◊. He is in his forties, and aside from having shorter hair now, he doesn't look a day older than he did in 1994◊.
Josh Groban is 33, yet he looks to be roughly college-aged.
Former AJW star Mimi Hagiwara◊ (on the right). 56 years old but you'd easily think she's at least 15 years younger.
Daryl Hall (b. 1946) and John Oates (b. 1949) of Hall & Oates, pictured here◊ in 2008. Seriously, they look better than most people half their age. Plastic surgery helps.
Another Buffy alumna, Alyson Hannigan, was 22 when she took the part of 16-year-old Willow, and 29 when the series ended. Not that you'd have known it, looking at her. Now that she's on How I Met Your Mother, she often plays her character's college or high school self in flashbacks, where she doesn't look out of place in a classroom full of actual teenagers. This is a recent photo of her at 38 years old◊ (she's the taller one).
Singer and Actress Leisha Hailey was born in 1971 but still looks like she is in her mid to late twenties.
Tony Harnell of TNT. Nearing 50, looks mid twenties to early thirties.
Hunter Hayes is in his early 20s, but still looks like mid-teens.
Holly Hunter◊ was born in 1958. She looks about 35 in most of her roles.
Doug Hutchison played Percy Wetmore in The Green Mile. Percy is supposed to be 21; Hutchison was 39 years old at the time. He told Frank Darabont that he was in his early/mid 30s. When he went to audition for The Salton Sea, the director told him he was 'too young', resulting in Hutchison having to show him his drivers license which proved his age. He's now in his fifties but still looks like he's maximum in his 30s if not younger. All of this events seems to be even more interesting if we remember that his character in The X-Files, the first Monster of the Week Eugene Victor Toomes was a mutant without aging process who looked absolutely the same in 1930s, 1960s and 1990s thanks to eating human livers ripped off alive.
Hutchison married model Courtney Stodden when he was 51 and she was 16. If that doesn't Squick you out, consider that because she's an example of Younger than They Look, they actually look like an age-appropriate couple!
At the time of his death, Isaac Hayes was 65 years old, yet hardly looked different then he did in the 70s when he was in his twenties.
Shirley Henderson was 35 when she first played the eternally 13-year old ghost Moaning Myrtle in Harry Potter and the Chamber of Secrets.
James Hetfield of Metallica doesn't look a day over 30, even though he's really 50.
During the 1990s, his beard made him look older than he really was (especially during the Load years).
Actress and voice actress Dana Hill looked like a teenager for most of her adult life. She suffered from Type 1 diabetes which prevented her from growing past a certain age and it tragically took her life at the age of 32.
One of the most common complaints, casting-wise, concerning Modern Family is the character of Haley Dunphy, who's supposed to be 16 but some say her character looks like "a tarted-up 12-year old." The actress portraying her, Sarah Hyland, is 21 years old. According to an interview in Nylon Magazine, she was nearly rejected for the role on the grounds of being too old (she was 18 at the time), only for her manager to assure the casting director, "trust me, she does not look 18." There are even flame wars on her IMDb page regarding her "real age."
Koshi Inaba the vocalist of the famed J-Rock band, B'z is currently 47. This◊ is one of his recent photos.
From this official portrait◊ (fairly recent; as it's from 2007) of Oklahoma Republican Senator Jim Inhofe. Inhofe is 79 years old but doesn't seem to look much older than 60.
Hugh Jackman still looks very good for a man in his mid-forties (born in 1968). In X-Men Origins: Wolverine, his physique is just as impressive as it was when he made the first film ten years ago. Pretty fitting as Wolverine is over hundred years old and still fights like a man in his prime.
Samuel L. Jackson, born 1948, certainly does not look like someone who's 65 as of 2013. He looks a good 15 or 20 years younger than that. He wanted to be in the Star Wars prequels because he was blown away watching the first movie in its original theatrical 1977 release when he was twenty-eight. In The Avengers, you would certainly never think he is thirty to thirty-five years older than most of his castmates. Which is especially funny as his character, Nick Fury, took a drug which greatly slowed the aging process and who is still at peak condition.
Who knew JAM Project's Masaaki Endoh, Hiroshi Kitadani and Masami Okui are in their 40's?
Philip Jeanmarie, who played Max in Power Rangers Wild Force, was around the same age as his castmates, being 24 during filming. Max is supposed to be in his late teens, and Philip looked the part. He's still barely aged and is now in his 30s!
Billy Joel is 65, and he does look kind of old, but that's only because of the hair. The face has stayed the exact same as it was 25 years ago.
Vincent Kartheiser, of Mad Men and Angel, was born in 1979 but barely seems to have aged since the mid nineties when he was teen. Even then, he looked younger (Larry Clark asked to see his driver's license before hiring him for "Another Day In Paradise" as he didn't believe he was eighteen at the time).
Jens Kidman of Meshuggah, anybody? He's 48 years old as of 2014, but not even his bald head prevents him from looking like he's in his mid-20s. Here's a recent photo.◊ As a bonus, he's the oldest person in the band, but looks the youngest. He even looks younger than bassist Dick Lovgren, who's 14 years younger than him.
Joan Jett absolutely counts. She was born in 1958 and looks the same age as people who were born when her first band formed.
A picture taken in 13 May 2013◊. Though, it is worth noting that other◊ contemporary pictures can give a greater impression of age, she certainly doesn't look to be in her mid 50's.
Aaron Johnson is 22 but could easily pass for a 15 or 16-year old. He's also a dad.
Amy Jo Johnson, another Mighty Morphin' Power Rangers alumnus, is in her forties, but looks half her age or even as young as her character Kimberly Anne Hart, the original Pink Ranger.
John Paul Jones of Led Zeppelin looks like he's in his 40s, not his 60s ◊
Milton Jones (British comedian) looks like he's in his late 30s. As of May 16th 2014, he is 50. This may have something to do with his deadpan style. Or his longish hair. This is him.
Michael Jordan turned 51 in February 2014, but he still looks pretty much the same as he did when he started in the NBA, and he was in his twenties back then.
Kendra Kassebaum, especially for a pale-skinned blonde. At 39, she still looked early 20's-ish, youthful enough to play Jovie in Elf: The Musical. She looks even younger than her 25 year-old castmate Jessica Skerritt (Deb).
This◊ is Enda Kenny, Taoiseach 2011-present, taken in 2013. He looks to be in his early 50s, right? Nope. He's 62—and Father of the Dail (longest-serving member of the legislature) at that.
Heather Langenkamp is currently 50 but she doesn't look much older than when she played Nancy in the original A Nightmare on Elm Street (1984), during principal filming she was 19.
Ray Liotta. He was on record saying, "It's the oily skin. It gives you zits when you are a teenager, but then it doesn't wrinkle as you get older."
James Lipton may not be the youngest man around, but he certainly doesn't look 86.
Heather Locklear is 51, but looks 10 years younger.
Alison Lohman could pass off as a teenager, if the dinner party scene in Drag Me to Hell and Big Fish are anything to go by. Her character makes use of this in Matchstick Men—the actress was 22 playing a girl of about 14/15.
John Longstreth is pushing forty, but still looks like he's in his mid-twenties.
Jennifer Lopez is in her 40s, but she looks at least 10-15 years younger.
Patti LuPone◊ in the 2011 New York Philharmonic production of Company, which was a week or two before her 62nd birthday.
This is professional wrestler Jerry Lynn in the old ECW◊ (circa late-90s to early 2000s). And this is Jerry Lynn in 2012◊. Aside from the lack of facial hair, he doesn't look much different than he was a little more than a decade ago. Can you believe that, as of 2013, Jerry Lynn's 50?
Ralph Macchio. He was 23 when the original Karate Kid was shot, but looked around 15, and now he is 51, but looks like he's just a bit older than half that age.
Even weirder, his voice hadn't even changed yet when the Karate Kid was shot!
When this picture◊ was taken, General Douglas MacArthur was 65 years old and already seasoned by three wars. This is him at 70 standing next to General Omar Bradley, who was 13 years younger. At the first glance, people would say the reverse was true.
Andie MacDowell was born in 1958 but looks more like she was born in 1988. Seriously. She not only looks young for her age, but looked young for her age in Film/Groundhog Day and hasn't aged one bit. She's 55 as of 2013 and could be convincingly cast as a teenager or college student and look more convincing than some 20-somethings who play teenagers.
Gabriel Mann (Nolan from "Revenge") is 40
Marilyn Manson managed to be this until 2009ish, looking like this◊ at age 37. And then he managed to beat decades of anorexia and proceeded to gain an extra chin◊. Thankfully, he's starting to regress in age again, playing a teenager◊ at the age of 43, and looking like he's in his mid-20s while doing so.
Shirley Manson of Garbage is 46 and looks around 30 - ◊
Demetri Martin was born in 1973, making him 40 in 2013. In his early 30s, he was brought on The Daily Show to host a recurring segment about America's youth culture.
James Maslow of Big Time Rush looks about 17 or 18, but is actually almost 22.
Jessica Erin Martin, famous for voicing Samus Aran in the most recentMetroid game, is about mid-20's, but looks 14-15, although she somehow was deemed "too old" when she auditioned to play an 18-year old role.
Steve Martin's white hair has given him a noticeably ageless look. He looks like he could be a lot younger than 68.
Chris Matthews of MSNBC appears to be in his early 40s but is 64◊.
Danica McKellar once looked about her age◊, a month and a half short of 25 years old, toward the end of 1999. Her looks seem to have frozen in time since then. Here she is over 14 years later, hosting the first edition of a new Nerdist video series called Math Bites, all the while looking like she hasn't aged a day.
Anthony McPartlin, of the English comedy and television presenting duo Ant & Dec, with the other being Declan Donnelly, was born on November 15, 1975. This picture of him from 2009◊ certainly does not make him look like he was 34 at the time, looking at least 10 years younger than that.
Idina Menzel. One look at this image◊ and I think most would be shocked to know she's 42.
Eminem (Marshall Mathers) is 41 but could easily pass for half that age.
Can anyone believe that voice actor Vic Mignogna is already 49 as of this writing?
Wentworth Miller is 41 but looks like early 30's.
This is Billy Mills (born June 30, 1938), a Native American runner who in 1964 became the only American ever to win Olympic gold in the 10,000 meters. Even in the picture where he looks oldest (top right of the page), he still looks somewhere in his 50s. Farther down the page is a picture of him receiving an award from President Obama in 2012. Does this look like a man in his mid-70s?
Elizabeth Mitchell is 42, but looks no older than 30, with some guesses as low as 22.
Masako Mizutani. It's no wonder why they're calling her "Japan’s Lady of Eternal Youth."
Demi Moore is in her 50s now but looks at least 10 years younger.
Julianne Moore is 51, and hasn't aged noticeably◊ in almost twenty years◊. This is especially bizarre when you consider how white her skin is; skin that pale generally doesn't age well. Also, her face tends to emote very well in movies, which is really hell on your skin. The only possible explanation at this point is she's a vampire.
Roger Moore was 45 when he was first cast as James Bond in the 70s. Moore is, in fact, 3 years older than Sean Connery, yet he looked much younger. That said, Moore started looking his age by the time his Bond tenure ended over a decade later.
Throughout the 90s and early 00s, Thurston Moore from Sonic Youth looked like he was in his early twenties while he actually was in his 30s and 40s, respectively. This applies to his bandmates as well, but then again, given the name of their band...
The former president of Egypt, Hosni Mubarak, is 82 and looks like he's in his fifties.
Comedian John Mulaney is about 30, but looks around 10 years younger. His voice doesn't really sound younger though. He discusses this in his comedy special, saying that he looks like an extremely stressed out child.
Frankie Muniz. He was 17 when he played Cody Banks, playing a 15-year old character who looked like he was twelve. He's now 27, and is just starting to look a bit less like a kid in his early teens.
Audie Murphy's birthdate is somewhat debated, but it's generally agreed that he had earned all his combat medals by the time he was twenty, looking younger than that, and was probably at least twenty-five when he got his first lead role...as a teenaged delinquent in the b-movie Bad Boy. He spent the next few years as The Trope Kid in various westerns, and then as a thirty-year-old, he played his wartime self moderately convincingly in To Hell And Back. He moved away from late-teens characters after that, but continued to play naive, early-twenties characters fairly convincingly til about 1961, by which point he was in his mid-to-late thirties. He got considerably more weathered-looking after that, due to his outdoorsy lifestyle and the insomnia caused by his PTSD.
Eddie Murphy just turned 52, but he still looks mostly the same as he did in his 20's.
In this video is actor Mitchel Musso, who is pranking one of his fans on a TV show. Watch the video and try to guess whether Mitchel or the fan is older. Done? Get this: Mitchel is 20, and the fan is only 15.
Recurring Cirque du Soleil contortionist Iuliia Mykhailova, at 27 going on 28, still looks like a 14-ish year old, suitable for playing the teenage heroine Miranda in Amaluna (2012-2013).
Dave Navarro of Janes Addiction and Red Hot Chili Peppers doesn't seem to have aged at all in twenty years. He's now pushing 45 and looks in his early thirties at most. This is despite being a member of two of the hardest rocking bands of the last twenty years and having taking an extreme amount of narcotics.
Liam Neeson looks like he's about 45, despite being 61.
Britt Nicole is 29, and her album covers made her look progressively more mature over time. Then her third album was re-released and the new cover makes her look younger than she did when first debuting... at 23.
Leonard Nimoy might be one of the most curious examples on this page: He actually used to look even older than his age... that is until he turned 82 and seemingly decided to reverse his aging process – but see for◊yourself. No "Trek Science" here, just the undeniable benefits of a full head of hair.
Takanori Nishikawa, aka TM Revolution: he is 5'3" and maintains the appearance of someone in their early 20's...but in reality he'll be 40 come September 2010. It's been said that he's so short because he didn't eat properly as a child. His youth despite his age is practically Bishounen level◊.
Masi Oka, being of Asian decent and only 5'6", counts as well, and seems to end up in a lot of Dawson Casting because of it (though his characters' age is rarely a plot point, when mentioned, it tends to be many years behind his own).
He was 32 when he started playing Hiro, who, depending on the episode, was either 24 or 28. He actually looked his character's age more than his own.
His character Max hasn't been given a specified age, but we know his biomom was killed in the 80s, making it likely that he's intended to be younger than his actual actor's age (he certainly still looks in his mid/late-twenties despite pushing forty). His love interest is played by an actress more than a decade his junior and the couple are neither treated as nor look like a May-December Romance.
In Searching For Sonny, he plays a 28-year-old despite being 37 at the time of filming. He also plays the 18-year-old version of his character in flashbacks, and a present-day photo is used as his high school graduation picture. Compared to his actual high school photo, though, the greatest difference seems to be in pounds rather than years (though you could certainly make the argument that 18-year-old Oka could pass for eight or ten due to being so small).
Adepero Oduye, star of Pariah, plays a 16-year old girl. She's 33. Her on-screen mom Kim Waynes (AKA The Wayans Sister) could count too, seeing as she's 50.
Dave Padden from Annihilator is 36 but appears to be in his 20s.
Carrie Paff looks about 15-20 years younger than her actual age (late 30s/early 40's). Blondes don't usually age that well.
Oddly, during her run on Heroes, when she was 18-19, some people thought she was in her late 20's. This was even alluded to when she was a victim in a Punk'd prank when a teen boy's mom confronted her about dating him.
Ellen Page is 25, but she could easily pass off as a teenager (and does, in several of the films she's in).
Grace Park is 40 years old as of March 2014... hard to believe, isn't it?
Korean Idol Singer Sandara Park is pushing her thirties, but looks◊way younger◊. When she debuted as a member of Girl Group2NE1, no one would have thought that she actually was 10 years older than then-15 years old fellow group member Minzy, even because she tends to act and sound like a teenage girl on a sugar high.
Jim Parsons turned 41 in March 2014. He looks, at the most, maybe 25.
The late Penn State football coach Joe Paterno until about 2007 looked no older than 50, despite being 80 at the time. But injuries from being very involved in practice (despite allegations of him being a powerless figurehead) have allowed for accidents to happen. After a myriad of injuries, he still didn't look 85, but instead closer to 70.
Adrian Paul looks pretty good for a man in his early 50's. But then, he IS the Highlander... Here he is just before his 54th birthday - he looks around 40! 
If you go to the YouTube video of Kate Pierson and REM singing Shiny Happy People, you'll almost certainly see a commenter hitting on her. She was 42 when the video came out, and is currently 64. This  picture was taken in 2012 and she looks twenty years younger than her actual age at least.
Rene Pinochet, a Chilean voice actor (best known as Aang), is in his mid-30's, yet he still looks and sounds like a child.
Brad Pitt turned fifty in December 2013. When he appeared in The Assassination of Jesse James by the Coward Robert Ford, he was aged up by makeup even though Jesse James was ten years younger than Pitt was at the time, although James' lifestyle made him look older. Although he has recently started to look middle-aged in his roles, he still looks much younger than other actors his age or younger.
Kyla Pratt. She's 24 (as of this writing) but would you know that if you saw her walking down the street? This actually leads to the "Prisoners of Pollyanna" problem, in that Pratt was a prominent younger actress, but because she looks younger than her age, some people expect her to act younger than her age.
Prince is in his 50s (55 to be exact, as of this writing), but he still looks the same way he did in the 1980s (which I'm guessing is around late-20s into 30).
This◊ is Ron Reagan (and before you ask, yes, he's related to thatReagan.) You'll probably peg him in his 30s, or maybe late 20s. He's actually 55.
Eddie Redmayne, 31 as of the time of writing this (November 2013), looks like he could easily be ten years younger than his real age - he plays a 20-year-old in Birdsong, and looks completely convincing◊.
Clémence Poésy, Eddie's costar in Birdsong, is only just 30 but looks like she's in her early twenties.
Keanu Reeves◊ doesn't seem to have aged at all since the nineties and sure doesn't look like he was born in 1964. In fact, some people think he is immortal and it isn't as crazy a theory as it sounds.
After seeing him as Hawkeye in Avengers, you probably wouldn't have guessed that Jeremy Renner is nearly 42.
Paul Reubens (better known as Pee-wee Herman) was in his late twenties when he created his popular Man Child character. Nearly twenty years later, when he made a career comeback by appearing as a superhero in Mystery Men he seemed barely to have aged at all despite being nearly 50. He's about 60 now and his face has begun to show some cracks, but with the right makeup he can still get away with portraying the Pee-wee character.
Christina Ricci just turned 33 as of 2013. She once complained she usually feels especially vulnerable in regards to her personal safety and security, as she not only looks like child-like, she remains the size of one per contemporary US standards. In her late-teens, she could still bemistaken◊ as someone a decade younger, if this film poster was any indication!
Condoleezza Rice is 59, but she looks much younger.
Cliff Richard is 73 but looks like a man in his 50s. Not for nothing is he known as the "Peter Pan" of pop music. This picture ◊ was taken in 2013.
Denise Richards turned 43 in February 2014. She just escapes the aging process, too.
Keith Richards, while not the world's most attractive man, certainly doesn't look like he's almost 70. Of course, the reason for this is obvious; he's well preserved.
Kimmy Robertson was 36 when she appeared on Twin Peaks'' and appeared in various commercials throughout the late 80s/early 90s. Because of her high pitched voice and stereotypical 80s hair/outfits, she looked like she could pass for a twenty something. Pushing 60, she looks like she could be in her mid 40s to early 50s. http://www.zimbio.com/Kimmy+Robertson
Mitt Romney◊ is 66, but looks more like he's in his 40's or (maybe) 50's.
Carol Roscoe(late 30's/early 40's), who has lately played several Dawson Casting roles, including Sheri in Pilgrims Musa and Sheri in the New World.
Morgan Rowe, a popular Seattle stage actress, not to be confused with others with the same name, 40's, looks about 15-20 years younger.
Ferris Bueller fans are usually rightly flabbergasted when they find out that Alan Ruck was 29 when he played, and legitimately looked the age of, 18-year-old Cameron Frye. He now looks his current age◊ (58 as of July 2014), however.
This is Paul Rudd in 1995, then almost 10 years later, in 2004◊, in 2007,in 2009, and now this year (2012). As of this day, the man is 43, and since 20 years the only thing that changed is his hair. Not only can he still pass as being in his mid-twenties: he stopped growing older in his mid-twenties!
Winona Ryder just turned forty. If not for her being in the business for over twenty years, it would be easy to think she was closer to thirty.
Filipina singer/actress Lea Salonga looked barely into her teens when she originated the role of Kim in Miss Saigon. She was 17 when she auditioned, 18 when the show opened. Now 39, she could easily pass for mid-20's.
His  co-star Jorma Taccone is even more noticeable. He was born in 1977 but looks no older than his mid-twenties at most. He even played Andy Samberg's younger brother in  despite being a year older.
Atticus Shaffer is 13 but looks eight - actually, he has IV Osteogenesis Imperfecta, so as a result, he's a lot shorter than average.
Shakira was born in 1977. Throughout her entire career, she could have easily passed for a teenager. Being barely 4'11" tall also helps.
William Shatner is in his eighties but could pass for a man thirty years younger. (The photo on his page is fairly current.) Consider that he's actually four days older than Leonard Nimoy (who looks good for being in his eighties but is visibly elderly)...
Jake Short of A.N.T. Farm is 16, but his lack of height and short stature combined with his then childish voice make him look at most 12. Even looking at his castmates China Anne McClain and Sierra McCormick, it's really hard to believe he's older than both of them. Think about this: Stefanie Scott, who plays the 16-17 year old Lexi on the show, is only 5 months older than him. It took the 2nd half of his 16-year old life for his voice to finally break.
Slash of Guns N' Roses doesn't seem to have aged at all since the 1980's. He's now 48 but doesn't look older than his early thirties. It helps that he has dressed exactly the same way since that time.
Will Smith still looks remarkably baby-faced in his 40's.
Pretty much nobody on the face of this darn planet will ever be 100% convinced that Little Richard is 80 (he'll turn 81 in December 2013). This is a recent photo of him.◊ He looks to be in his early 50s at most, despite having no plastic surgery.
Identical twin actors Dylan and Cole Sprouse definitely qualify. As of this writing, they are both 19, old enough to be freshmen in college. However, despite this, they barely look old enough to be freshmen in high school. Which is pretty stupid, since they were supposed to be seniors in the later episodes of Suite Life on Deck, but still looked like they were around 14 years old, although able to pass as a little older. And when they were 16 in the first season of the show (playing sophomores), they looked about 11. The fact that their voices took years to crack didn't help either. This led to people believing that they were actually younger than their characters during the third season of Zack & Cody, as their characters were both to be freshmen in high school, but the twins still hadn't hit their first growth spurt and their voices were still undoubtedly childish despite being 15 years old at the time.
Now 20, however, they have definitely grown up since leaving Disney, though they look more like they're in their mid or late teens now, so they're looking much closer to their real age.
Ringo Starr just turned 73 years old, but he looks 50 at most.
Patrick Stewart is 72, but could easily pass for 50's. Hell, look at the first episode of Star Trek: The Next Generation in which he's 47, and you'd be hard-pressed to tell him apart from today. Which is really a subversion, because despite some extra wrinkles and filling out a bit, he looked like the same old bald man we know and love when he was in his 30's. Which makes the younger, full haired cadet seen in the episode Tapestry hilarious.
Sting is 62 and doesn't look much older than 45. Must be all the tantric sex.
Regardless of whether it's due to expert plastic surgery or really fortunate genes, one would probably be shocked if they knew that the lovely Meryl Streep is 64.
Keith Strickland of The B-52's, age 59, has not aged visibly at all for much of his life, which is largely down to his healthy lifestyle (he's a buddhist, vegetarian and keeps constantly active). The only visible difference is that he has shorter hair these days. Cindy Wilson also looks extremely good for her age, having been a mother.
Sarah Stiles (Joanne in Vanities: The Musical, as well as Lucy and Kate Monster in Avenue Q) is 32 (30 at the time of the off-Broadway production of the former), but looks and sounds teenage.
Could I direct your attention to a certain prominent politician from a certain South East Asian country? This◊ is her in 1995, and this◊ is her immediately after release from house arrest in 2010. Did I mention she was 65 at her release?
Voice actress Tara Strong is 40, but looks like she's in her late 20s.
Arika Takarano, the lead singer of ALI PROJECT. She looks like this.◊. She was also born in 1963. SHE'S FORTY-SEVEN.
Marisa Tomei is currently 49 at this time (2013) but looks much younger.
Louis Tomlinson will turn 22 in December 2013. He looks, at the most, maybe 16.
Alessandra Torresani (known from Caprica) looks about 14-15 but is really 25 (born 1987). Oh yeah, she has a black belt in taekwondo and has shown in a video interview with Wired that she's able to kick ass in 6 inch heels, her Combat Stilettos.
Jerry Trainor from iCarly. He's playing Spencer, a man in his mid to late twenties, but he looks like a college student and acts like one. Jerry is 34.
Denzel Washington, a few grey hairs aside, barely seems to have aged since He was in Cry Freedom back in 1987. He's now 58, but seems perfectly at home in action films with actors twenty to twenty-five years younger.
Naomi Watts is 44 and looks to be in early 30's. She is even set to star in a 2013 biopic about Princess Diana despite being almost a decade older than Diana was when she died.
Gerard Way of My Chemical Romance is 35 but still somehow seems to age backwards. This is despite all the drinking, drugs, coffee, and his ridiculous smoking habit.
Anyone who saw Avatar thought Sigourney Weaver looked darn fine. She's 62.
Interestingly, Wilson's longtime friend and Opeth frontman Mikael Akerfeldt, who he's often pictured with, looks quite a bit older than him but is actually 7 years younger than Wilson. It's not that Akerfeldt looks bad for his age, it's just that Wilson looks so young for his.
Elijah Wood, as of the time Part 1 of The Hobbit releases, is 31 years old. He doesn't look much older than he did when he was 18 years old and working on the Lord of the Rings films.
"Weird Al" Yankovic is 54, but doesn't look any older than his mid-thirties. In fact, thanks to removing his ridiculous glasses, afro, and mustache he had in the 80's and 90's, he actually looks younger than he did when he was actually young.
Check out this video, then look at how old they say Winfred Yu is. He looks about 20 years younger.
Tay Zonday is one of the most extreme examples. He's 30 years old, but looks like he's in his late teens at the very most. His voice is also extremely deep and doesn't fit him, to the point it almost looks like he's lip-syncing in his videos. His page image on this wiki was taken when he was 25.