Five in Detective Conan: Shinichi's mother Yukiko, former prize-winning actress and Black Organization member Vermouth who actually trained with Yukiko; the Kaitou Kids who also starred inMagic Kaito — Kuroba Kaito currently and Kuroba Toichi formerly (who trained Vermouth and Yukiko), and Phantom Lady who trained Kuroba Toichi — and married him.
Some of the above five have helped other characters out with their disguises: Shuichi Akai, who has been posing as Subaru Okiya to keep an eye on the Black Organization and protect Ai as he promised to her dead sister. Yukiko is the one who trained him, too. And Bourbon, probably trained by Vermouth.
Masaharu Niou and Hiroshi Yagyuu from The Prince of Tennis. They pretend to be each other during a doubles match, after all.
Mercilessly parodied with Koharu and Yuuji, who use disguises not to conceal their identities but to disrupt their rivals's concentration. And to provide a whole Crowning Match Of Funny. To beat them Momoshiro and Kaidoh had to become Masters of Disguise, using lucha libre masks to confuse them back.
Ren from Tower of God successfully infiltrated Evankhell's Hell by dressing up as the instructor Yuga. Though that might not have been that hard, considering what Yuga looks like◊.
Lupin III, grandson of the Literature example, Arsene Lupin. In order to keep up with him, the rest of the cast, as well. However, Lupin is the best. Everyone else has had their disguises fail utterly at one time or another. Lupin can be unmasked, but it often seems to come only when he planned it that way. Two major examples from the series:
An episode of Lupin III (Red Jacket) has Lupin, Goemon, and Jigen disguised as Zenigata. When they're caught together, Goemon and Jigen admit their in disguise, and drag off the real Zenigata, claiming he's Lupin and they should surrender.
Lupin Family All Stars: Every character is disguised as another character, except for the one disguised as the man in the iron mask. (the story comes from a manga chapter)
Lupin's Bride, another character inspired by the Literature example, from Cats Eye. Her debut episode has her stealing a painting by posing as the artist who created it, with the real artist Bound and Gagged off-screen.
Also, the Kisugi sisters, AKA the titular thieves. Their usual disguises are those of random police officers or invented persons, but Rui has disguised herself as either Mitsuko Asatani or Toshio (the latter was problematic and led to Toshio being Mistaken for Gay, as Rui has issues at actually acting like a man), and Hitomi has easily disguised herself as anything and anyone.
The manga-only character Masato Kamiya, AKA the Phantom Thief known as The Rat, makes liberal use of disguises, mostly as a police officer. The Kisugi sisters can usually see through his disguises with little problem, but nobody else can, and he even managed to fool Rui in one occasion.
In one Axis Powers Hetalia strip, China vents his frustrations to a panda and talks about how he's sick of all the foreigners and how Russia's planning to backstab him. The panda takes its head off, revealing Russia.
In Mahou Sensei Negima!Anti villainess and Fate's minion Shiori has a specialized kiss that can steal the full appearance of the one she kisses, as well as the ability to lose her consciousness and think she's the person. Needless to say, no one figures it out once she switches with Asuna... until they meet up with the Governor General, that is. And it still takes quite a while to unmask her.
The series also has Kazumi Asakura, who's capable of becoming indistinguishable from whoever she chooses in order to (in this case, Shizuna-sensei) get the big scoop. Main lead Negi only managed to tell the different thanks to the Marshmallow Hell she gave him, seeing as even though she's not bad herself, Asakura just couldn't compete with Shizuna.
Schwarz Bruder from G Gundam is shown to be this in episode 18, where he took the form of an old man. It's not surprising, since he's ninja and all. He doesn't use this often though.
In Monster Johann dresses up as his sister twice. Once as a child for a completely inexplicable reason and then later as an adult just in order to fuck with everyone.No one saw that coming. As a variation on this trope he also proves a master of disguising his identity and real nature (through sheer charisma) from various people right up until it's too late for them to do anything about it.
MW has Michio impersonating every female victim he kills.
Mr 2, Bon Clay from One Piece can take the shape of anyone he's touched. He isn't that comfortable acting the part though...
Ranma ˝ has Tsubasa Kurenai, a oneshot (twoshot in the anime, with a pair of cameos) character whose specialty is dressing up in elaborate costumes, mainly of inanimate objects, which allow him to blend in perfectly to his surroundings if he chooses. He's been a mailbox, a statue, the sign outside Ukyo's restaurant, a trashcan, a kasa-obake, a vending machine... and underneath the costume, he also dresses in women's clothes as an expression of his love for BifauxnenWholesome Crossdresser Ukyo Kuonji. He's so good at impersonating a woman that just about everyone he meets actually thinks he is one at first. He even has a girl's voice (unless he's angered; in that case, his voice becomes as male as you can hear it from someone his age)!
Another oneshot, Copycat Ken was a paparazzo who stole martial artists' techniques by becoming them and using all of their moves against them. The only one he couldn't copy perfectly was Happosai, because he was just too perverted. So he trained Ken. He ended up with so many copies that he started mixing them up and became unable to change back.
Hannya from Rurouni Kenshin, to the point that he actually mutilated his own face to make the process easier. The result is horrific, and it's understandable why the anime didn't include that bit (only showing us one of his eyes).
In the manga, Gein—The Dragon to Enishi Yukishiro, the final Big Bad—proves to be a Master of Disguise as well. He was disguised as his own puppet, Iwanbou, in order to spy on Kenshin from within Shishio's group—and Shishio, himself a Genre Savvy villain who's always on his guard with most other people, never gave any indication that he knows of Iwanbou's true nature.
Team Rocket from Pokémon disguise themselves as somebody or another, sometimes crossdressing, or in the case of Meowth dressing as another species, on average once an episode. Jessie "Jessebella" "Jessadia" "Jessalina" "Jessilinda" "Jessilynlyn" "Jessirilyn" has used so many deviations of her name with rather small (relatively — her big dress up costumes are usually very detailed) changes to her outfit it isn't even funny. Ash and Co. never figure out who Team Rocket is until they out themselves — if they figure it out at all.
Early in the series, Team Rocket were legitimately good disguising themselves. As they became less serious antagonists (a transition that didn't take very long at all), their disguises became more and more paper-thin.
A oneshot (well, two-shot) character, a girl named Duplica, was also a quick-change master, even able to impersonate Ash, Nurse Joy and Officer Jenny in a flash. Her Pokemon of choice was, of course, a Ditto, and loosely based on Copycat Girl from the video games.
There was also the Phantom Thief Brody in the Hoenn series.
Green/Blue (the female one) of Pokémon Special, through creative usage of her Ditto as a sort of Latex Perfection mask. Her disguises include Sabrina during the Rocket Team HQ assault in the Red/Blue arc and the old man with the Abra in the Pokemon League during the Gym Leader battle of the Gold/Silver/Crystal arc. Even Silver, the one who she's been with for the longest time, wasn't able to identify her until her Ditto flowed off to reveal her true face.
The Latias who's friends with Emerald is also able to do this by manipulating the refraction of light. She's actually a lot easier to identify than Green/Blue. Just look for females with her distinctive hairstyle.
Petrel has proven to be this in the HGSS arc, dressing up as the Johto Safari Zone owner, Eusine, Silver and Lance... in the same page.
Fullmetal Alchemist Envy is an example of this. Oftentimes he will disguise himself as various members of the army to get to places that he otherwise could not go. He also uses his power of shape shifting to confuse people and take advantage of them. He used this tactic when he kills Hughes by disguising as Ross and Gracia. In the manga and in Brotherhood, he constantly uses this power to keep his monstrous identity hidden and in the original anime by hiding his identity as Ed and Al's eldest brother..
Kenichi: The Mightiest Disciple: Saiga Furinji reveals that he's capable of this. To what degree? He was disguised as the fat, short, bumbling, jolly mercenary John for most of the rescue mission to save Miu from Silcardo Junazard. To put it in perspective, Saiga is much taller and leaner than the John disguise, capable of cowing the members of YAMI's Nine Fists by simply speaking, and is physically capable of beating down several skilled assassins while covering up his daughter with his jacket.
What makes it even better is that Sakaki Shio, one of the Ryouzanpaku masters and therefore someone you'd expect to be skilled enough to see through such a disguise, doesn't suspect anything at all.
A little known one-shot manga by Kigitsu Katsuhisa (Creator of Franken Fran and Helen ESP) named Phase 20 has the mysterious legendary thief who calls himself "Twenty Faces". As the name implies, he's a pro at blending in and going by undetected.
A rather curious subversion in Kimagure Orange Road. Kyousuke's cousin Akane is not a shapeshifter herself, but a psychic... and her Psychic Powers include making you believe she's somebody else you know. As far as we know, no other empowered Kasuga can copy said ability.
Aria the Scarlet Ammo: Riko Mine is another thief character with the ability to disguise themselves excellently. Because she is the great-granddaughter of Arsene Lupin, and Holmes's nemesis.
Kill la Kill has Nui Harime, who disguises herself as a male student in order to draw Ryuko out of a Heroic BSOD and destroy Senketsu. The only hint as to her true identity before The Reveal is when "he" greets Mako from a stall in the girls' bathroom, plus the fact that she couldn't take off or move her distinguishing eyepatch, so she has it covered with her disguise's hair..
The Chameleonian alien from Space Dandy is so good at disguising itself, it can actually make they person it's disguised as think that they're the Chameleonian.
Mystique, X-Men - she's a shapeshifter, and is quite comfortable as either a man or a woman. On the other hand, she has more difficulty maintaining a shape that is different in mass than herself. For example, when she spent a few years pretending to be a Governor's wife, using the name Mallory Brickman, part of her disguise was that she was about twice her normal weight. Since she was going to have to maintain this image for a very long time, she gained weight, to bring her own mass up to the same amount as "Mallory".
Shapeshifter, one of the main villains in Comico's Elementals series.
Diabolik and his partner Eva Kant from the Italian comic Diabolik. The only way to unmask them is to pinch their faces to check for Latex Perfection... And even that has failed on occasions due them being particularly creative or simply opting for Wig, Dress, Accent (this happens so rarely that the police never sees it coming).
The Chameleon, an actor turned assassin who once came gunning for Jonah Hex.
Ninjas in Empowered. One of them even disguises as a dog!
The Spirit: his arch-nemesis The Octopus is an accomplished Master of Disguise. As he is also The Faceless, the only clue the reader has to his identity at any time is when his hands are visible; he always wears purple gloves with three yellow stripes appliqued onto the back. It has been established that he has the same height, weight and general build as the Spirit, so he frequently chooses to impersonate the Spirit in order to implicate him or to confound the cops into shooting at the wrong guy.
Lord Shilling, the British spy who was the Arch-Enemy of Tomahawk, was a master of disguise.
Averted with George in With Strings Attached. Though he can become a perfect copy of anyone, he knows he can't adequately pull off an impersonation because he can't readily suppress his accent, act, or otherwise seem convincing. When he has to become the woman Bayanis, he spends the entire time praying no one will ask him to say or do anything. When he becomes a goblin, every detail about him besides his shape is wrong, and he has to rationalize every one of them when he is questioned. Luckily for him, in these cases no one is expecting an impersonator.
Spoofed in Attack of the Killer Tomatoes! by Sam Smith, a black man who disguises himself as such notable non-black people as Hitler, Abe Lincoln, George Washington, and a blonde girl, all while making not the slightest effort to disguise his skin color. He even managed to convince the tomatoes that he was one of their number, until he forgot and asked for ketchup.
Zelig (played by Woody Allen) is pathologically capable of blending in with important people, due to a childhood need to fit in. This enables him to impersonate a surgeon, a sex god, and a member of Hitler's inner circle (among other politicians), despite having no particular skill, and being Jewish. He can even change his race, causing the Ku Klux Klan to pronounce him "a triple threat".
Despite being the Trope Namer for Clark Kenting in the comic canon, the first Christopher Reeve film turned Superman into one of these. Like Richard Hannay in the Literature example below, his success had less to do with props than body language and vocal mannerisms.
In the old Basil Rathbone/Nigel Bruce Sherlock Holmes film series, Rathbone was nearly impossible to identify most of the time, other times his nose gave him away. Also, just scroll down a little to the literature section for more info.
Kirk Lazarus of Tropic Thunder is a master actor. He is a blue eyed blond haired Australian playing a black Sergeant and while he was doing that he managed to pose as a Vietnamese Farmer.
Eames in Inception can pose as anyone during dream when necessary. Thus, he's called "The Forger."
Artemus Gordon in Wild Wild West. He can become President Grant, a fur trapper or a rather ugly woman. (He isn't perfect, however. His Grant disguise didn't fool West because he was drinking from a Harvard shot glass, and West knew that the real Grant went to West Point.)
Gordon and Grant actually share an actor. Kevin Kline did a great job of playing Gordon-as-Grant doing an almost perfect impression of Grant.
In Cars 2, both Finn McMissile and Mater become this, thanks to voice-activated holographic disguise systems that let them instantly assume any appearance.
Undercover Brother. Undercover Brother uses Latex Perfection twice, to appear as an elderly janitor and James Brown. He uses ordinary disguise techniques to become a Rastafarian golf caddy and corporate executive Anton Jackson.
In Adele Hasn't Had Her Dinner Yet, Nick Carter is America's greatest detective and his disguises are "proverbially perfect", however, his intention to blend in with the crowd fails epically when he arrives in Prague. His books had perfect information about people and their life in the Bohemian countryside, but apparently not so much about life in towns, so he's immediately recognized by the Director of Police and a newsboy. Nick is also not pleased to learn that everything gets noised abroad in Bohemia and that his arrival was not kept a secret. However, his disguise as Professor Bocek was amazing, down to being a Master Actor, and also his disguise as an Arabian gentleman when he was leaving for Egypt was truly impressive.
Horace Badman alias Hogo Fogo in Lemonade Joe. He sports wigs, fake beards and moustaches, glasses, dark glasses, hats, make-up... His own brother didn't recognize him when he was disguised as a black trumpet player and an old blind man.
Julius Caesar's unnamed spy from the Astérix movie Asterix Meets Cleopatra, he disguises himself as everything from a brick to a plate of fruit.
Sherlock Holmes. Since he rarely warns even his allies about this, he's managed to (almost?) get himself arrested at least once. Oh, and he's equally good at faking himself-plus-condition, from mortal illness to opium addiction, whenever it serves the case he's on.
He does point out that it's painful to take a foot off your height for hours on end.
He also FREQUENTLY fools Watson and several Inspectors, amazingly enough.
At least once, Holmes's disguise was also mostly due to acting, in "The Final Problem"—Watson is supposed to meet Holmes at a train station, and instead is joined by an old Italian priest in a cassock. The priest changes his expression for a moment and Watson realizes it's Holmes. (The cassock is his only physical disguise.)
Then there's the pastiche character, his sister, Enola Holmes, who regularly fools him. Knowing how he thinks certainly helps and she plans her disguises accordingly.
Subverted in the Richard Hannay novels by John Buchan: while the main character disguises himself frequently and successfully, it is more through acting than characterization.
Buchan's thesis appears to have been that if you're a good enough actor you can disguise yourself from even people who know you well. The main character's best friend is a particularly good actor, and is always unexpectedly appearing in books, sometimes from behind the face of a villain.
The original Arsčne Lupin, gentleman thief, had this down to an art, and inspires several imitations.
Fantômas, the villain of his own series by Marcel Allain and Pierre Souvestre, is one of the more brutal examples of this. One of his defining features is always appearing in various disguises and then getting rid of the persona through faked deaths, explosions, and mass murder. The same is true of his rival the Inspector Juve, sans the death count, who uses an equal number of disguises to try and bring Fantômas to justice.
Alias in the Evil Genius Trilogy, who teaches Disguise at the Axis Institute, and frequently arrives to class disguised as one of his own students. One of the 3 teachers that escaped the institute alive.
The Avenger. Richard Henry Benson, of the 1930's pulps was a master of disguise. He suffered a horrible emotional shock which deadened the nerves in his face which he could mold like putty. (Ah the innocence of the 30's!) He carried around a disguise kit with wig, contacts, make-up etc to go along with the putty face. Later when his face came back to life he invented a serum which had the same effect.
Doc Savage, which is pretty amazing when you consider his extraordinary physical appearance — roughly 6'6" (2 meters) tall, perfectly muscled, bronze skin and eyes, and yet he frequently fools his closest associates.
The Shadow was a disguise master in his magazine adventures; made slightly easier in his case considering how few people ever truly saw his face.
Face Loran from the X-Wing Series. He uses makeup and prosthetics, but his main tools of disguise are his extensive acting experience and the fact that he comes from a planet whose hat is observation and control of body language.
Nom Anor in the New Jedi Order. His people, the Yuuzhan Vong, have genetically engineered a creature called an ooglith masquer that acts as a second skin that can alter the wearer's features dramatically, even allowing them to impersonate members of other species (though since they're basically humanoid, impersonating some species requires more extensive alteration). Anor, though, is a master actor and spy on top of that- with a masquer and the right prep time, he can fool anyone except a Jedi (since the Anti-Magic nature of the Vong means they don't show up in the Force).
Erast Fandorin is so good at this that some characters get confused, which of his appearances is the real, original one.
Betty Bent from the Kiki Strike books: Her parents are costume designers for the Metropolitan Opera, and she's so good at disguising herself that can appear as pretty much anyone the Irregulars needs her to be.
She had a Freudian Excuse for disguising herself: Betty explains to Ananka in the first book that she used to be really weird-looking, and people would make fun of her for how she looked. So she started disguising herself so people wouldn't give her a hard time about her looks.
The villainess in The Girl With The Golden Bouffant, a Les Yay spoof of James Bond, isn't recognised despite turning up as a girl in a mink bikini or a stewardess conducting an 'intimate' lifebelt drill demonstration on the heroine.
Jay, from the Paladin of Shadows series after the first one. Kurt Schwenke is also suggested to be this, in A Deeper Blue.
Nymphadora Tonks from the Harry Potter series is a metamorphagus who can change any part of her appearance at will, which she says was very helpful in the disguise section of her Auror exams.
Count Olaf from A Series of Unfortunate Events, being an actor, has an infinite amount of costumes at his disposal, especially from his evil troupe. He's been everything from a Sikh gym teacher, to a submarine captain, to a carny. No one second guesses the tall lanky man with an eye tattoo on his ankle except the Baudelaire kids.
Fernald, a.k.a. "the hook-handed man." is arguably even better, since even the Baudelair kids fall for his disguises. And he doesn't even have to take off his hooks to do it, he just hides them.
Sauron in The Silmarillion, thanks to his Shapeshifting ability, turns himself into a giant vampire bat, a giant werewolf, and the most friendly, helpful, likeable, not-at-all-evil angelic being you'll ever meet (not). Beren and Lúthien successfully shapeshift themselves into Elite Mooks by wearing the pelts of their demonic enemies.
The Confidence Man has the confidence man himself. He sneaks on a riverboat on April Fools' Day, and puts on more than eight different disguises, becoming a different character tailored to be one that would be able to con money out of each passenger, all while testing the confidence in their morals and perception.
Moist von Lipwig. Though this is equal parts disguising himself and his natural appearance; he was born with the most forgettable face in the world, the sort of person that someone would look at and think, "I wonder if I've seen that man before", but he never seems like more than a face in the crowd. He's average in every way, which helps him blend in anywhere.
Agent Pendergast has an almost superhuman ability to look like a different person with little more than a change of clothes. In Reliquary, he even makes his disguise as a hobo more convincing by imbibing an illegal hallucinogen.
Burke from Andrew Vachss's books is no shapeshifter, given the hard-realistic setting, but with the aid of makeup, changes of clothes and putting on a different persona has been able to pass himself off as different people
Faceless Men in A Song of Ice and Fire are assassins who through their training are able to completely alter their appearances. Some kind of magic is involved, but also basic theatre techniques if that will suffice.
Toni Ware in The Pale King has at least twenty distinct voices and differently-colored contact lenses.
Time Scout's Chuck Farley. He disguises his face, his mannerisms, everything.
Tzigone of Counselors and Kings is a former street performer and natural mimic, which allows her to pull a dizzying array of impersonations- particularly since she's flat enough to pull a convincing male. It's very hard to pick Tzigone out of a group of people if she doesn't want you to (the fact that half the Big Bad Duumvirate has been after her most of her life makes such skills essential).
Vigilante ManMack Bolan calls this "role camouflage", which is based on psychology rather than physical disguises. He knows that no-one will associate the friendly telephone repairman or smooth elite hitman from New York with the notorious blacksuited One-Man Army.
The Master in the classic series tended to do this, up to the point that BBC credited the actor with an anagram to keep up the suspense. Leon Ny Taiy = Tony Ainley anyone?
The new series Master manages this due to The Nth Doctor. Nobody realizes Professor Yana is him, and he later regenerates into Mr. Saxon, a mystery figure who's been hovering at the edge of things all season. He then travels a year back in time to become said Mr. Saxon. As usual, there's a Significant Anagram: Mister Saxon = Master No. Six. However, The Powers That Be have said that was wholly unintentional, and that when a character's title is simply "Mr.," it's easier to make a Master anagram than avoid one. However, Saxon really is the sixth form of the Master: there's Delgado, zombie, Ainley, US film, Prof. Yana, and now Mr. Saxon. Assuming you count both actors playing the zombie as one incarnation, and don't count Gordon Tipple from the start of the film. Or the twelve incarnations before Delgado we never saw.
It's lampshaded, along with Paper-Thin Disguise, in "The End of Time". A botched resurrection leaves the Master stuck with his old, highly-recognisable face and no resources. He's reduced to dyeing his hair, wearing scruffy clothes and trying to stay out of sight.
The Master: The master of disguise... stuck looking like the old Prime Minister!
The revival had Nicholas Black: he was the one to wear the Latex Perfection masks because he had an acting background.
Arch-enemy Murdoc from MacGyver was said to be a master of disguise. But his disguises were so bad that viewers only fell for them because his appearances were spread out enough that the audience had forgotten what he looked like.
Christopher Chance, star of the comic book and quickly-cancelled TV series Human Target, though comicverse Chance doesn't impersonate, he becomes (often resorting to surgery, which is kind of cheating.)
In the original comic books, he often relies on disguises.
An episode of CSI: Crime Scene Investigation had an old Vegas mob boss who was thought to be dead come back as one of these, killing his betrayers with a different disguise.
Jared, the Pretender from The Pretender, had an entire series based around this. While he never changed his physical appearance, he would adopt an extremely wide array of different jobs, mastering all of them in an astonishingly short timespan.
JAG had several. The eponymous assassin Hemlock in ”Hemlock”, rouge DSD agent Clark Palmer in ”Imposter”, and Al-Qaeda associate Sadik Fahd in ”Persian Gulf”.
Parodied by Col. Flagg of M*A*S*H, who thinks he's one of these, while in reality absolutely anyone can see through his disguises. Mostly due to the ridiculous ones he tries to pull off.
The Lone Ranger put on fairly good disguises not too infrequently, since all he really had to do was remove his mask and add a beard or something - and the beard was more to keep the audience from seeing his true face, since if he were to ever show himself just plain maskless to other characters on the show, only Tonto would ever know who he was.
False Face from the Batman TV show (who was based on a one-shot comics villain).
Sylar from Heroes recently joined the members of this trope. In addition to a ton of other powers, goshdangit.
Several characters in Super Sentai can do this, mostly the Pink Rangers.
One memorable battle from Kyoryu Sentai Zyuranger even had Mei fighting the villains' master of disguise, Lamie, with both often switching costumes.
Also it is noted that in Dai Sentai Goggle Five, Goggle Pink/Miki Momozono is designed to be a Shout-Out (or Expy) to Cutey Honey above, since she just needs to spin around to change clothes without flinging them off (even going as far as switching from Goggle suit to a sexy Flamenco dancer outfit right off bat).
Shurikenger made his own version. He has no name or human appearance. As a result he has nodefiniteactor other than his voice actor. His human form is always that of some passerby, played by a past sentai hero, until he reveals himself by transforming — with the past hero's transformation pose! (Except Battle Kenya's; since they didn't have transformation poses, Kenji Ohba's Shurikenger awesomely, hilariously does his Space Sheriff Gavan pose, which is much more elaborate than any sentai one.)
The Dolls of Joss Whedon's Dollhouse are imprinted with many different personalities for their engagements.
One of them, however, is portrayed by the friggin genius named Enver Gjokaj, who can be everybody, and probably is. His acting alone is reason enough to watch the show.
Prince Ludvig the Indestructible from the second series of Blackadder is this. It proves to be his undoing, as his overly-elaborate costume at a fancy-dress party sets him apart. But then in The Stinger he somehow disguises himself perfectly as the queen (still played by the same actress but with his voice).
Get Smart has at least three episodes about Disguise Masters. First one is about the man who pretends to be Chief to kill a very valuable witness. Second one is about the leader of ACB (third organization; it has both CONTROL and KAOS as its enemies) who disguised himself as fellow agent (one of the first on-screen black agents). Third one is about Chameleon: he disguised himself as Larabee, Admiral Hargrave and even as 99, all to infiltrate a secret counsel.
Spoofed in Monty Python's Flying Circus, with a contact agent disguised as a dog. He proudly describes the painful-sounding surgery required to fit him into the costume. On screen, he looks more like a victim of taxidermy.
The Changelings in Star Trek: Deep Space Nine are actually a race of almost liquid amoeba that can change their shape to about anything. While the changeling in the main cast can only rudimentarily mimic humanoid features, more skilled ones can impersonate any person and even fooled close friends for years.
Speaking of Star Trek, Isaac Asimov once suggested to Roddenberry that Kirk might make a good one of these.
Because he's a hologram, The Doctor on Star Trek: Voyager can mimic anyone so long as an image of them is uploaded into the main computer.
In The A-Team, team leader John Smith did this at the start of every episode, but he only used it to fool potential clients until he decided they were O.K. Then he'd take off the disguise right in front of them.
Tim: You say you're the Most Naughty Man in the World, how come we've never heard of you?
Nasty Person: Because I am a master of disguises. Look, these are some of my greatest triumphs! [unveils pictures of Richard Nixon, Enoch Powell, Idi Amin and David Frost] All me!
Later they fool Nasty Person's brainless henchman into thinking he's disguised himself as the Goodies, all three of them. At the same time.
Square One TV: In the Mathnet serial "The Kalpurnian Kugel Caper" Mathnet's CIA contact is a master of disguise, at various times disguised as an old lady, a dog, and a llama. Subverted when George thinks that the CIA man is disguised as a lamp pole.
In the music video for "Beautiful Stranger" this is used by Austin Powers chief Basil to explain the many looks of Madonna, portrayed as a Mata Hari who has seduced the top agents of British Intelligence.
Gene Simmons' "Man Of 1000 Faces", from the KISS solo albums. "I can put on any face; you won't know me, but it's no disgrace."
Also a possible in-universe explanation for the "Ninjutsu" mechanic from the same block, where an unblocked attacking creature can be replaced by a creature with Ninjutsu, already attacking. A possible explanation is that they're retroactively assumed to have been perfectly disguised as the creature they replace.
Any Exalt with Charms dedicated to disguise can be this. Solars, in particular, can convincingly disguise themselves as anything up to and including a decently powerful local deity.
With the appropriate stunt in Spirit Of The Century, characters can disguise themselves thoroughly enough that they don't even have to declare in advance what they are disguising themselves as. They simply declare that they are going undercover and leave the party. At any later point, they can declare that any of the background NPCs is really the player in disguise.
There are several Pr CsPrestige Classes in third edition Dungeons & Dragons that focus on this skill, focusing on creating and maintaining cover identities and gaining certain bonuses to using them. The Pr CPrestige Class descriptions mention that use of these methods is usually cover for less legal activities. Everyone has the 'disguise' skill available to them, but these extra classes are where the masters are.
The Callidus assassins of Warhammer 40,000 wear this as their hat. They dose themselves with polymorphine, a drug which allows humans to shapeshift as long as they have the required mental discipline; everyone else gets an instant Shape Shifter Swan Song. On top of this, the Callidus are capable of mastering the voice and mannerisms of their targets after only a few moments of observation, and even store weapons inside their flesh. Their only weakness seems to be impersonating Tyranids; they can do it, but it's a one-way transformation.
A number of Inquisitors can also lay claim to this trope. Notably, enough Inquisitors have disguised themselves as Rogue Traders over the centuries that it's become a stereotype in-universe.
The Alpha Legion are an entire Legion of eight foot tall killing machines that can disguise themselves as either other Space Marines or normal humans. And if they can't pull a particular role off, they'll draft Mooks who can.
Decoy Octopus from Metal Gear Solid is quite possibly the most detail-obsessed Master of Disguise ever, being able to flawlessly mimic a person's speech and mannerisms, and either ingesting or injecting himself with the blood of the person he's imitating. But he's unable to fool The FOXDIE pathogen, which kills him.
In The Last Days Of FOXHOUND Octopus becomes a straight-up shapeshifter: He can disguise himself as anyone (including Berthold, who is a wolf) by using specially prepared solutions of the target's blood, and assimilates all of their physical mannerisms including genetics, physical abilities, and... Clothing? Better not think too much about that one. At one point, Mantis and Ocelot even force Octopus into obtaining a Liquid disguise just by force-feeding him Liquid's blood. The comic's continuity even explains how FOXDIE is able to kill him in spite of his freakish genetics: It was programmed to kill all witnesses to Shadow Moses, including the person Octopus was disguised as at the time.
Although not to the level of Decoy Octopus, Liquid Snake himself is also implied to be this as well, especially seeing how he managed to disguise himself as Master Miller.
Mimi from Super Paper Mario is astoundingly good at this, at least in looks; she can't pull off the personality of her target terribly well.
The Spy in Team Fortress 2, when in disguise, looks exactly like the person he's imitating—body shape, face, and voice.
It also shows that looking the part doesn't make a person this trope. Bad spies are fairly easy to tell apart (and kill) from real teammates, since they often don't act like the class they are playing as. Good spies, however, are often impossible to tell apart from your allies until the knife is in your back.
To add more fuel to the Paranoia Fuel fire, a Spy can disguise as his own allies. Why is this useful, you ask? You're still going to be shot down by your enemies. However, if you fake your own death using the Dead Ringer watch, your enemies will think "Okay, I just killed that enemy Medic/Pyro/etc.", making their death by backstab all the more unexpected!
The dragons in World of Warcraft are able to assume humanoid forms, generally High Elvish, but there are exceptions, such as human or even gnome forms. Notably, Onyxia used to live in the human city of Stormwind, under the disguise of human Lady Katrana Prestor, where she was subtly influencing political decisions to the Black Dragonflight's favor. Some dragons appear to be worse than others at this: thus, the leader of Red Dragons Alexstrasza takes on the guise of a Blood Elf of High Elf, but even in the guise she keeps her distinctive dragon horns and red color. Since she doesn't actually hide the fact she's a dragon, perhaps she does this on purpose.
Agent 47 in the Hitman series is truly a master of disguise. Being able to take on the identity of pretty much anyone without raising an alarm. Despite being bald and having a barcode on his head. Granted, his disguises (that is, changes of clothes) are meant to hold up to cursory examinations, aside glances, and to people who haven't met the person he's impersonating. In the first three games this often even crossed racial and ethnic boundaries, but in Blood Money he could no longer disguise himself as someone with a notably different skin tone.
Sasuke from Sengoku Basara has the ability to perfectly disguise himself as other characters using ninja techniques.
In Pokemon Heart Gold And Soul Silver, Petrel desperately wishes he was this (he keeps make-up in his belt for just such a purpose), but the two times he disguises himself (As Giovanni in Team Rocket's hideout and as the Director in the Radio Tower) are completely pointless, and his disguise fails to fool the player anyway. Amusingly enough, the player's disguise works perfectly, until your Rival comes along...
In Pokémon Platinum, Looker claims to be a Master of Disguise (he uses the exact term) and admittedly, he manages to get into the Team Galactic base undetected by disguising himself as a Grunt.
Don Paolo, in the Professor Layton games, crosses this with Latex Perfection. Thus far in the series, he's flawlessly impersonated everyone from Inspector Chelmey of Scotland Yard to teenaged girl Flora to Professor Layton himself!
Parodied in the SPY Fox games, where Fox only has to put on the Mook uniform to get past the real ones. However, he still needs to go into more depth in order to get past advanced security.
This is the talent of the Super High School Level Impostor in Super Dangan Ronpa 2. At the beginning of the game he is disguised as (and introduced to everyone as) Byakuya Togami, one of the survivors of the previous game. It's a pretty exact disguise - except that the Impostor weighs twice as much as Togami does. He isn't revealed until long after his death, but his Free Times and Dangan Island segments reveal that he has impersonated multiple people in the past and has almost no identity of his own.
To a lesser extent the Baroness and Scarlett were both masters of disguise, but they used rubber masks. Scarlett invariably botched it anyway, but Baroness could easily be, for example, a highly decorated prison warden.
Oddly enough in an earlier episode, Ron Stoppable pulled off this trope, using a latex mask to impersonate Mr. Dr. Possible. In a later episode, Monique helped Kim impersonate Camille after Camille framed Kim for stealing an upcoming fashion line.
Imp from She-Ra: Princess of Power was typically used by the Horde for information gathering against the Rebellion. He was very much able to shapeshift into any form he wanted and his transformations were so flawless the characters encountering him in a shifted state tended to treat him accordingly. Examples include Kowl perching on top of him when he was a footstep in a ladder, Bow tossing him when he became a stick, and Catra even drinking from him when he was mimicking a goblet. Though most of his transformations tended to retain his blue color scheme, on at least two occasions (as a ground rodent and as a hanging painting) Imp showed the ability to alter his coloration at will. The only limitation here seemed to be Imp wasn't able to become anything more massive than himself, although he did take on the abilities of whatever thing he was pretending to be.
Part of She-Ra: Princess of Power's every episode was to watch the scenery for the character Loo-Kee, who tended to be hidden amongst the scenery. While sometimes he was easy to find, there were several times it was very difficult to pick him out of the background. It's not sure if this would count as being a Master of Disguise, but it certainly makes him a Master of Hiding.
The title character from Walter Melon who would regularly take on the appearance of the heroes he was substituting for, could do so so well that apparently even those with intimate knowledge of the hero were unable to spot the difference (with one exception when he did his Karate Kid, the expy of Mr. Myogi claimed he watched Walter Melon and stopped him before he could kiss Daniel's girl). Simultaneously he wasn't the only one as his assistant Bitter Bug and his rival Sneero also displayed such ability, typically taking on the roles of needed sidekicks and villains respectively without anyone noticing.
Its interesting to note that, though Walter and Sneero encountered each other during almost every episode of the show, neither one ever recognized the other as a substitute hero/villain.
Also, in the same series, Amelia, who always takes the role of the female lead and yet nobody notices it.
The antagonist, Transfer the wolf, from Around the World with Willy Fog is a sinister master of disguise hired by London Club to ensue Willy Fog lose the wager. Viewers can spot his disguise from the way his one eye gleams red.
American Dad!'s Roger is perhaps one of the best example of this trope. He literally has an entire closet full of disguises, and usually ends up disguised at least once (if not multiple times) per episode. Of course, many of his disguises are Paper Thin, but no one seems to notice, most of the time.
From Transformers Prime, Makeshift. He was apparently capable of transforming into anyone he wanted. He was also killed off at the end of the episode.
Brain from Inspector Gadget is an interesting case. Whatever he wears never seems to be more than a Paper-Thin Disguise to to the viewers (due to the fact that, well, he's a dog) but he strangely seems to fool almost everyone else with them.
Doug from the Regular Show episode "Temp Check" is able to make himself look and sound exactly like Rigby, and even somehow memorizes almost everything about him, making himself indistinguishable from the real thing.
Octus (a robot) in Sym-Bionic Titan normally takes on two disguises: Newton and Mr. Lunis. It's shown that he can alter the appearance of the latter, when hiding from the cops and the former when trying on a prom tux.
The Snooper and Blabber short "Person to Prison" has criminal Quick-Change Quentin, who can perfectly disguise himself as anybody and anything.
An episode of Top Cat has a criminal who can do this, and uses this to disguise himself as Officer Dibble.
Octopuses are well known to be much better at changing their color than even chameleons. The Mimic Octopus however, has specialized in impersonating completely different creatures like flatfish, snakes, giant shrimp, lion fish, seahorses, sea anemones, jellyfish, and seemingly whatever else it wants. It not only assumes the form of the creature, but also acts like one, fooling most other animals. In fact, their existence wasn't discovered until 1998.
SS chief Heinrich Himmler was only apprehended because he'd worked so hard on preparing his forged documentation that it was actually suspicious to find someone who had all his papers in the chaotic Germany of immediately after the war's end.
Another Chilean example: actor and stand-up comedian Stefan Kramer.
Ted Bundy: Part of the reason he was able to elude the authorities for so long was his generic looks, which allowed him to completely change his appearance very easily.
Capt. Kazimierz Leski of Polish Army. After the fall of Poland in 1939 he began to operate for the Underground State as intelligence and counterintelligence officer. He was traveling across Europe, usually impersonating various German officers and specialists and extracting vital information for the Allies. He has been captured several times (by Soviets, Germans and Soviet-controlled Security Officein post-war Poland) but was able to escape using his disguise skills.
Isadore Einstein (No relation to Albert Einstein), the Man of a Thousand Faces. His talent at disguise helped him make nearly 5,000 arrests in his five year career as a Prohibition officer.
Dutch actress and media personality Wendy van Dijk◊ is famous for her tv-shows in which she disguises herself as a foreign interviewer and fools unsuspected guests. Her most famous character is the Japanese reporter Ushi◊. Other characters include Loesie◊ and Dushi◊.
Lon Chaney, the silent movie actor, was so famous for his skill with makeup that he was called "The Man with the Thousand Faces."