King Henry V in Kenneth Branagh's film on William Shakespeare play Henry V. King Henry dresses himself as an archer and visits his troops during the night before the battle of Agincourt, using a pretty transparent name "Harry Leroy". Harry is, of course, colloquial from Henry, and while Leroy is a Welsh name, it is also French for le Roi, "king". When one of the archers asks him if he is of Welsh origin, he answers affirmatively; before he became king of England, he was Prince of Wales.
Lampshaded in Mystery Men, when the city's resident superhero appeared as his mundane counterpart. There was an argument between two of the titular Mystery Men at one point, in which The Shoveler insisted that they couldn't be the same person because the regular guy wore glasses - and the superhero didn't. "He wouldn't be able to see!"
Subverted in Men in Black. When Agent K points Frank out to Agent J, appearing to indicate a weird-looking man at a newsstand, Jay says, "Bad disguise, that guy is definitely an alien." However, as it turns out, Frank is actually the pug dog next to the guy.
Played for laughs at the end of the same film. When Jay tells Weaver that Dennis Rodman is an alien, she says, "Really? Not much of a disguise." (Any NBA fan would probably "get" the joke quickly; those not in the know would probably be helped by knowing that Rodman is square in The Tyson Zone.)
The titular character in Corky Romano's skinhead outfit screams "I'm trying to pretend to be a skinhead" His bald head wig his so obvious and he as a fake "No menorahs" tattoo that state how he's trying way to hard.
He's found out because he's trying way too hard to blend in.
Corky: "Wanna go commit some hate crimes"
The Princess Bride: Despite being his true love, Buttercup can't figure out who the Dread Pirate Roberts is based on the fact that he wears a Zorro mask and hair wrap. She's also blindfolded when they first meet and has plenty of time to listen to his voice before looking at him. Justified because up to this point Buttercup believed the man in question was dead, and the Dread Pirate Roberts' sharp and authoritarian tone is very different from the soft and loving words he had used before.
In The Seeker, the Black Rider spends most of the film disguised as an extremely goofy country doctor with huge glasses and a tweed suit.
In A Hard Day's Night, all it takes for Super Famous Beatle Ringo Starr to slip into anonymity as he wanders around London is a cloth cap and an overcoat. The disguise even lasts when he loses the overcoat, so the cloth cap must have special powers. Reaches heights of absurdity when, having been arrested, Ringo insists to the policemen that he's Ringo Starr, but they refuse to believe him - because he's wearing the cloth cap.
A couple of fangirls see through the disguise at one point, forcing Ringo to make a hasty retreat.
Similarly in Help!, the Beatles go to the airport in fake beards and mustaches to avoid being noticed by Cult members.
To be fair, in Help! those were much more elaborate costumes. John even went so far as to stay in a wheelchair to avoid recognition, far from simply wearing a cloth cap.
In Enchanted, Nathaniel goes unnoticed in a restaurant kitchen because he is wearing a chef's hat as his only disguise element. And his disguise when he's peddling apples from a cart in Central Park isn't much better either.
Done in the old WWII propaganda film Beasts Trom The East. The Japanese soldiers are disguised as trees throughout, even when moving or shooting.
In Attack of the Killer Tomatoes!, a guy tries infiltrating the Tomatoes at a campfire wearing a tomato suit; he actually fools them until he blows his cover by asking for some ketchup.
This trope was quite commonplace in the short films of The Three Stooges. In one, the boys end up cooking/catering at a party for a judge who wants to send them up the river. Moe: "Oh, he'll never recognize us in these outfits!" (Apparently, just wearing a white jacket and chef's hat renders you totally unrecognizable.) In another Western-themed short, Curly masquerades as a Justice of the Peace, but is not recognized by Christine McIntyre until he lifts the tiny (and I mean tiny) little toupee off his head, points at his face, and mugs.
In the Live-Action Adaptation of Cutey Honey, the title character had several costumes/disguises, but she invariably had bright red hair. Imagine it; you're in a Tokyo train station full of girls with black hair, and you're trying to find Cutey Honey. How long would it take you to spot the redhead?
In Velvet Goldmine blue-haired rock star Brian Slade turns up to a concert in a "disguise" consisting of a large hat and coat. Although his ex-wife reveals that she recognised him, and public opinion towards him had already soured somewhat, it seems a bit odd that no one bats an eyelid at his appearance, given that he is still very famous, and very poorly disguised◊.
In What's Up, Doc?? one of the characters attempts to disguise himself by wearing a fake mustache. Not only that, but it's upside-down. The main characters seem to realize who he is, though.
Two female soccer players in Shaolin Soccer disguise themselves as men by sporting a fake mustache and goatee and talking in a deeper voice.
In Friday the 13th Part 2, Ginny convinces Jason she's his mother by simply putting on Pamela's sweater and acting like her. Jason eventually does see through the ruse, but only after spotting his real mother's severed head.
In the live-action version of Teenage Mutant Ninja Turtles (1990), the turtles wear trench coats and fedoras when walking around the city. Even though they're worn at night, these disguises do nothing to hide their bulbous noses, bulky shells, or the fact that they're far more massive than most humans. This is even lampshaded when Raphael rolls over the hood of a taxi cab.
Passenger: What the hell was that?!
Cab Driver: Looked like sort of a big turtle, in a trench coat.
In The Legend of Zorro, Zorro's son is unable to recognize his own father's face or voice, while talking to him, because part of Zorro's eyes are covered by his facemask.
Parodied in Hot Shots! Part Deux in a Shout-Out to the film The Guns of Navarone. When intercepted by an Iraqi patrol boat, the heroes pretend (poorly) to be local fishermen. Ramada's disguise consists of a very fake looking mustache. The soldiers don't notice anything amiss until they enter the ladies' room, but even then they assume that the fishermen are just perverts.
The Rocky Horror Picture Show: Dr. Frank. N. Furter fools both Brad and Janet with his paper thin disguises, first as Brad to seduce Janet and then the other way around, and all he's wearing for a disguise are glasses and a wig for Brad and a wig for Janet. Then again, it's dark in both of their rooms and he seems to be able to imitate their voices perfectly.
In the Star Wars Prequel Trilogy, Palpatine doesn't do much more than wear dark robes and speak in a raspier voice to disguise his identity, in spite of being a public figure. (Of course, one thing that helped was, until Palpatine was revealed as a Sith Lord, very few people knew that "Darth Sideous" existed. Only a few of his minions and the leadership of the Separation Forces knew about him, and other than Darth Maul and Count Douku - first probably knowing about his dual-identity and the second certainly knowing - he only communicated with them via a hologram, which blurred his image and helped hide his identity.)
Played straight and averted in The Major and the Minor, where Ginger Rogers' character dresses like a little girl to take a train for half price. The Major falls for it, as do the cadets at his school, but most other people realize that she can't possibly be under twelve, with an actual teenage girl pointing out her distinctly adult features and the fact that she's acting more like she's six than eleven.
In Heroic Trio, Anita Mui's character wears a small mask that molds to her face so much that it shouldn't really fool her husband. Judge for yourself here◊ and here.◊
Played with in the first of The Green Hornet movie serials. One episode has the gangsters trying to steal an election, and they use the classic "wear disguise and vote multiple times" method. Some of the reporters watching the polls see through the rudimentary disguises. However, it's not clear if the disguises were paper-thin to make things easier for the audience or an attempt by the gangsters to give the poll workers Plausible Deniability — the gangsters used bribes other times ....
In a later episode of that serial, we learn that Kato's costume as the Green Hornet's chauffeur is exactly what he wears as Britt Reid's chauffeur, right down to the same driving goggles. No one ever makes the connection. To be fair, Reid normally drives himself unless he's going someplace fancy, in which case paying attention to the servants is Not Done.
Played with in Green Lantern. Hal Jordan's Domino Mask is supposed to protect his identity. After saving Carol Ferris' life, Hal appears at her window in his Green Lantern persona in an attempt to "get the girl". Carol almost immediately sees through his disguise, pointing out that she had known him all her life and she wasn't dumb enough to not recognize him because she couldn't see his cheekbones.
Parodied in the Telugu film Alluda Majaka where the main character, Sitaramudu, puts on a wig (which is an exact copy of his hair) and a moustache (that is an exact copy of his own), doesn't change the way he speaks at all and nobody recognises him.
From the film, The Devil and Miss Jones, Joe puts on a fake mustache and a hat and thinks nobody will recognize him as the leader of the rebelling workforce. It doesn't work.
The 'men' at the stoning in Monty Python's Life of Brian are all women with fake beards. They keep forgetting to speak in a lower voice and refer to each other as "she" before catching themselves. Ironically, many of the women in drag are actually played by members of Monty Python, who often play female characters.
In Zookeeper, Griffin (Kevin James) and Bernie the gorilla (voiced by Nick Nolte) sneak out of the zoo and go to a TGI Friday's (It Makes Sense in Context). How is it pulled off? Griffin simply has Bernie wear a shirt and they pretend to have come from a costume party. Works like a charm.
In Chitty Chitty Bang Bang, the Child Catcher disguises himself as a candy vendor by putting a coat on over his normal clothes. Yeah, that coat made him look completely different. But said coat was enough to fool Jeremy and Jemima, who had seen him earlier.
Likewise, the two spies' various outfits.
In She's The Man, it's fairly obvious when twins Viola and Sebastian (played by Amanda Bynes and James Kirk) are on screen together no one could possibly confuse them for the same person. However, it is lampshaded and justified in the beginning because no one at the school had seen Sebastian before. But later on, it becomes less plausible.
In Sky High, The Commander almost only differs from Steve Stronghold by the glasses the latter wears, as Layla points out...
This trope gradually came into play for the 1972 film adaptation of Sleuth. The young Michael Caine's "Inspector Doppler" disguise was genuinely convincing to audiences forty years ago, and resulted in an astonishing reveal moment. But to current audiences sitting down for a re-watch, the fake inspector looks uncannily like a present-day Michael Caine, so the surprise has been retroactively spoiled.
In The Phantom of the Opera (2004), the Phantom uses a Don Juan disguise for "The Point of No Return." It just about works, but fails because Piangi (the real Don Juan) is noticeably heavier-set than the Phantom, and, as it turns out, a little more dead.
The stage version tries to make this slightly more plausible by using a heavy floor-length cloak with a deep cowl for the "Don Juan" costume. Some Phantom actors even emulate Piangi's Italian accent in the scene. It still doesn't explain why nobody notices the guy performing with Christine is suddenly about a hundred pounds lighter, though...
A particularly baffling example occurs in an old Polish comedy Poszukiwany, Poszukiwana ("Wanted" in masculine and feminine forms, respectively), where the protagonist, accused of art robbery, has to prove himself innocent while disuised as a woman. The thing is, 1) he doesn't wear any makeup at all, 2) he uses his normal voice all the time, 3) he doesn't fill his flat chest with any fake cleavage, not to mention that 4) his clothes and hairstyle are very outdated even for 1970s Poland. He basically looks like a man wearing woman's clothes and a wig, and yet somehow everyone around falls for it. In one example particularly, a guy he works for as a house help walks in on him shaving, without any disguise, in male's pyjamas... and all he has to do is to quickly put on his wig and cover his stubble with a towel, explaining that he has a toothache.
In the filming location sense, in the first two films of The Dark Knight Saga, Batman Begins and The Dark Knight, Christopher Nolan did practically very little to hide the fact that Gotham City is represented by Chicago, to the point that there are people who spend more time trying to see what Chicago landmarks they can recognize than following the story.
The same goes for The Dark Knight Rises and its filming location of NYC. In one aerial shot you can clearly see the new World Trade Center being built. Also, taxicabs that clearly have the words "NYC Taxi" on the sides can be seen in a number of scenes.
You can also clearly see the Heinz signage on Heinz Field in Pittsburgh, used for filming Bane's football stadium attack.
The film version of How the Grinch Stole Christmas! this ugly cave creature puts on a red coat and Santa hat. Boom! He automatically looks "just like Saint Nick."
Partially justified as a way of keeping people from noticing him from a distance (i.e. "a figure on the roof tops in a Santa's hat on Christmas eve must be Santa!") When Cindy Lou approaches him, he tries to keep the tree between them to help keep her from seeing him properly.
In The Muppets, when the Muppets become "Muppet Man", Miss Piggy doesn't notice the head looking like Fozzie with a mustache. After she finds out it's them she says that she can't believe she fell for Muppet Man.
In Muppets Most Wanted, all that Constantine needs to do to disguise himself as Kermit is to put makeup over his mole. While he does look exactly like Kermit otherwise, he barely tries to act like him or hide his accent.
Mostly avoided in The Film OfThe Return of the King. In the book, Éowyn was able to hide her identity from everyone while she rode with the other Riders, including Merry, who was with her. In the film, there was no way for Éowyn to be disguised in a way that the audience wouldn't know it was her straight away, so while she rode in a helmet that concealed part of her face (which would keep those less familiar with her from realizing who she was, thankfully, in an army of several thousand people from all over the country, she could probably find some unit to hide within that wouldn't know the king's niece on sight), she didn't bother hiding her identity from Merry.
Subverted in The Man with the Golden Gun where James Bond tries to pose as the assassin Francisco Scaramanga and gain information from one of his clients simply by wearing a fake third nipple. (Bond thinks this will work, because nobody knows what Scaramanga looks like, and he has always, up to now, dealt with his clients via intermediaries; the third nipple is his only known distinguishing feature.) Unbeknownst to Bond, Scaramanga has a new goal in mind and has met with this client personally this time, so the guy isn't fooled, but plays along with Bond for now.
Parodied in the spoof movie Loaded Weapon 1 with Jigsaw (Tim Curry) in the beginning. He's dressed up as a Wilderness Girl (basically a lawyer-friendly version of the Girl Scouts), but he has a thin beard, is tall, and doesn't make any attempt to disguise his male voice. Somehow, he still manages to gain entrance to York's house despite the horrible disguise.
In North by Northwest, Roger Thornhill briefly tries to avoid drawing suspicion in a train station simply by wearing a pair of sunglasses, but the staff aren't fooled for a minute. Arguably justified as at that point the sunglasses were probably the only thing he could find that had any chance of concealing his identity. Subverted later on when his newfound friend Eve Kendell helps him get off the train by borrowing a luggage handler's uniform.
Averted in Cinderella (2015). Ella brings up that her step-family will see her so in a Hand Wave the Godmother makes it so the family won't recognize her. And then Lady Tremaine figures out it's her anyway.
Parodied in Bill by King Philip II of Spain who disguises himself by wearing a false moustache (over his real one), everyone is fooled and shocked to see it's him when he removes it.
Averted in Hussar Ballad, as the main character, Shura, looks very much like a young man while in uniform, despite being an attractive girl. Director spent a lot of time looking for an actress capable of pulling this off.
It gets better: her body double was a young male stuntman, and it's nearly impossible to notice him replacing her.