Jose Cuervo did an ad about "living the high life", which was all about this trope.
Anime & Manga
Virgin Night: Hiroki tries to pass himself off as a scion of a family of business bigwigs in "Nadeshiko Innocence", because he's so utterly ashamed of the fact that he's nearly the polar opposite (it may be implied in the beginning that he's a Ronin, but he might also or instead be a Starving Artist in training, given all the sketches of Nanako), and can't bring himself to "afflict" Nanako with the truth.
Ayame in Silver Spoon is from a perfectly ordinary family who just got rich by some circumstances, but she acts like an arrogant Ojou, with all theassociated tropes. She acts normally with her parents though.
One of the murderer in Detective Conan pretends to be the daughter of a rich family so that her friends like her. She works very hard to be able to take them hiking, camping, and even to Hawaii. Turns out her friends and her boyfriend know about her and are only using her for her money and are planning to suck her dry. She ends up killing her so-called 'best friend' and blame it on her boyfriend
Kaby Melon in Fairy Tail desperately wants someone to burn a certain book, so he promises Natsu and Lucy a lot of money that he doesn't have. In order to seem like he actually has money, he dresses in fine clothes and borrows his friend's huge mansion. However, Natsu reveals the act by realizing that Kaby's smell and the mansion's smell are different.
There's a Will Eisner comic depicting a well-dressed couple on a dinner date at an expensive restaurant. When they go to their respective homes at the end of the date, each are revealed to be Mock Millionaires, and obviously unaware of each other's lack of wealth.
In a comic version of Mickey's Rival, Mortimer turns out to be one of these.
In one Sherman's Lagoon arc, in order to impress his classmates in a high school reunion, Sherman has Hawthorn help him pose as a CEO. Things go sour when Hawthorn takes the ruse too far and starts selling fake stock for a fake company.
Sherman: So now I'm going to fake jail?
Hawthorn: Here's where the reality kicks in.
The original Puss in Boots has the cat Puss convince the king his master is a nobleman.
Films — Animation
Al's first wish in Disney's Aladdin amounted to this, though it might be a borderline case. After all, depending on how the Genie's magic worked, Al really is a millionaire after his wish is granted.
A variation occurs in The Princess and the Frog, where Prince Naveen really is rich, but has been cut off by his family. He still pretends to be well-off in order to marry a rich woman. Also Lawrence, since he is disguised as Naveen as part of Facilier's plot.
Detective Carter follows a Hong Kong crime boss onto a yacht party. He hits on an attractive woman by claiming to be the owner of the yacht.
Later in the movie, Carter and Lee are at a Las Vegas casino in pursuit of counterfeiters. To distract the guests from Lee's attempts to sneak into the back, Carter begins gambling wildly and waving bundles of (counterfeit) money.
In Bottom, Richie and Eddie join a dating service, and Richie gets a date with Lady Natasha Letita Sarah Jane Wettesley Olstomsky Ponsonsky Smythe Smythe Smythe Oblomov Dub, Countess of Moldavia. Richie pretends to be an eccentric millionaire with Eddie as his butler.
The Frank Capra film Lady For A Day has a woman named "Apple Annie" who has been telling her daughter in Spain that she's part of New York's high society. When her daughter arrives with her fiancé, the son of a Spanish count, Annie has to be a genuine Mock Millionaire and Princess for a Day to avoid derailing the engagement.
A similar vein was explored in Six Degrees of Separation with Will Smith. Smith poses as the illegitimate son of a famous celebrity and while he does not pretend to be rich himself he implies that his father is paying for his education at an exclusive school and that he knows all the right people in upper class society.
In an old black'n'white movie, an actual millionaire who fell in love with a poor, aspiring actress, and pretended to be a normal guy (a traveling salesman, to be precise) because he figured she'd be intimidated if she knew. Hilarity Ensues, and eventually, he's asked to act like a Mock Millionaire to fool the girl's boss, with nobody involved (except for him) realizing that he's actually a millionaire. Would probably count as a subversion...
In City Lights, the Tramp uses his friendship with the Millionaire to allow his (blind) love interest to believe he is rich.
The movie Metropolitan is about a group of young upper-class Manhattanites blithely passing through the gala debutante season. They are stirred by the arrival of Tom, a Mock Millionaire who's actually a middle-class boy.
In the movie Penelope, "Max Campion," the child of a wealthy Blue Blood family that gambled away the family fortune, is recruited by a tabloid reporter to court Penelope, the reclusive daughter of a wealthy family who is secretly cursed. Her curse can only be lifted when she is accepted "by one of her own," so her parents are soliciting other blue bloods as prospective husbands and Lemon (The reporter) figures a broke blue blood can get in and will need the offered reward. It is revealed, however, that "Max" is actually Johnny, broke musician and gambler who was sitting next to Max Campion at the poker table when Lemon showed up for the recruitment.
Gone with the Wind has Scarlett trying to pass off a set of curtains as an expensive gown in order to impress Rhett Butler.
In Disney's The Monkey's Uncle, Darius Green III not only turns out to be one of these, it's revealed he has escaped from a lunatic asylum.
The Mask of Zorro has Antonio Banderas' character, a bandit, posing as a Spanish aristocrat, with the original Zorro pretending to be his valet.
In Some Like It Hot, one of the two main characters pretends to be the owner of Shell, even going so far as to host a dinner date on someone elses yacht to convince Marilyn Monroe to fall in love with him.
(talking on cellular phone) "How did the market close? Uh-huh. Well, roll over my amalgamated, split my utilities, and double my capital venture overlays. Now call me in an hour, and tell me what the hell I'm talking about!"
In getting into character in Cypher, Morgan begins effecting traits of a globe-trotting playboy; wearing finer clothes, indulging in top-label scotch and cigarettes, referring to exotic locations he's traveled to on his yacht. Subverted, as those are all qualities of his true personality, a genuine billionaire.
A variation occurs in Fitzwilly, where Miss Woodworth is unaware she's a Mock Millionaire.
In Lord of War, budding Arms Dealer Yuri pretends to be a millionaire to impress his supermodel wife-to-be. Of course, when his business takes off, his wealth ends up "surpassing the lies about [his] wealth".
Essential in the plot of Spanish movie Hay que educar a papá.High-Class Glass -wearing Count De Ronda is discovered to be a con man.
It is the plot of the french Movie Jet Set. A poor actor pretends to be an Italian prince to hang out with movie stars. Some of the rich people he hang out with discover the truth, but choose to help him anyway.
"Oily" Carlisle, among quite a few other P. G. Wodehouse characters, pulls this as a scam. Several other Wodehouse characters stumble into it as well, such as Sue Brown in the Blandings Castle novels Summer Lightning and Heavy Weather.
In an O. Henry short story, "Transients in Arcadia", the hero and heroine do this to each other.
"The Necklace" by Guy De Maupassant is about a woman who borrows a friend's diamond necklace for a party to pretend she's well-to-do but then loses it and spends the rest of her life trying to pay for a new one only to be later told it was fake.
In The Count of Monte Cristo, the Count gets a disreputable old soldier and Benedetto, a career criminal, and son of one of Dantes' enemies to pose as father and son and pretend to be wealthy Italian aristocrats. Dantes as the Count might also count (pardon the pun) — he is legitimately wealthy, but he's posing as an aristocrat, although being familiar with the peerage, the other character know that the island of Monte Cristo doesn't have a count.
Technically he's really a Count, but he bought the title, rather than inherited or earned it. Owning land is one of the requirements, so he used the uninhabited island of Monte Cristo for this purpose.
Reacher Gilt from Going Postal might qualify. Though he conducts himself in a very lavish manner, throwing grand parties and dining at expensive restaurants, it might all be part of his masquerade as a Corrupt Corporate Executive. He himself teaches that wealth is an illusion, and stole the Grand Trunk through embezzlement and accounting tricks. It's never clear how much actual liquidity he actually has; in the end, when he is caught by Vetinari after fleeing the city, he's clearly disheveled and impoverished.
Granny Weatherwax in Maskeradedefinitely does. To try to get into the opera house, Nanny Ogg uses the proceeds from her book to make Granny look like a lady. Granny just acts like herself, and her overbearing, towering arrogance is enough to intimidate everyone into not questioning it.
The Mark Twain story The £1,000,000 Bank-Note — a poor American traveler in London is given this by two men as part of a bet. He is expected to return it in a month. By presenting it and asking for change, he obtains a reputation as an eccentric American millionaire, obtains credit, and becomes rich in the end through investments. This story was adapted into the movie Man with a Million starring Gregory Peck.
In the Dawson's Creek episode "Kiss", Joey pretends to be wealthy to avoid looking like a small-town girl when she pursues a handsome stranger named Anderson.
In the Baywatch episode "Vacation", Guido pretends to be "Count Guido Popadokulous" in order to romance Mrs. Kenilworth, a wealthy middle-aged widow. It backfires when she wants to sleep with him; even after he tells her the truth, she still pursues him.
Was also explored recently in an episode of Castle. That Mock Millionaire is a con artist initially intent on bilking his heiress fiancée, who then fell in love with her. He is then killed by his partner to avoid potentially ruining the con.
White Collar has Neal do this a good chunk of the time during investigations, especially since he's already got several rich fake identities already set up (to say nothing of the fact that he's The Charmer and a verySharp-Dressed Man, adding credibility to the image). Plus, it's fun to make the government pay for you to throw a bitchin' party.
When they can't use Neal in the role, Peter will usually step in as a self-made down-to-earth millionaire.
The team themselves use this on a regular basis to con their targets.
An episode has a client house-sitting for a millionaire and pretending to own the house to impress his new girlfriend. The deception works just a little too well: he attracts the attention of some kidnappers, who assume anyone living in a house like that can easily obtain 5 million dollars to pay the ransom.
Kramer on Seinfeld attempted multiple times to pull this off under the pseudonym H.E. Pennypacker. Jerry also tried it once using the name Kel Varnsen ("Advantage Varnsen!"), as did George as Art Vandelay.
Done twice in The Monkees; once so that Peter could romance a debutante, and another time to convince Davy's grandfather he is a success so he won't force Davy to return to England.
One episode of Veronica Mars introduces the richest kid in Neptune, who arrives to school in a limousine and lives in the biggest house in town. The twist ending is that he's the son of the butler, and thus is actually not rich.
Anthony DiNozzo Sr., Tony's dad, on NCIS, is a formerly wealthy businessman, who is trying to keep up the appearance that he is still wealthy.
It later turns out that while Tony believed his father had been wealthy until recently, DiNozzo Sr. had actually been near bankrupcy several times during and after Tony's childhood, but managed to avoid it every time by pretending to be wealthy until he found a way to bounce back.
Done on a regular basis by the crew on Hustle. Sometimes the mark turns out to be this as well.
One Victim of the Week in Unforgettable was an abused West Virginia housewife who fled to New York and successfully passed herself off as the heiress to a fictional Texas oil tycoon. She was murdered by her publicist when she tired of living a lie and wanted to come clean.
An episode of The Love Boat had one of the ship's laundry workers pretend to be wealthy to court a young woman who had been dragged onto the cruise by her mother trying to marry her off to whatever rich man they could find. Naturally the ruse is exposed but they still end up together and even the mother accepts it ("I didn't lose a daughter, I gained free dry cleaning!").
An episode of House had Taub running into and treating his former high school classmate Neil who invites him to his fancy office and asks him for advice on improving a medical device he invented. Taub, who misses his former privileged life, had just lost a bunch of money in the housing bubble crash and had gone through a particularly humiliating day with House asks him for a job and he proposes they become business partners. Taub hands his resignation to House and goes to meet Neil with the money...and finds a secretary who tells him that Neil was just a temp using the CEO's office to con a bunch of doctors out of their money (using the "high school classmate" and fake illness ploy for all of them) and was just arrested. Taub then spends the entire following episode trying to convince House not to fire him.
In Game of Thrones, it turns out that the legendary vault of Xaro Xhoan Daxos, "the richest man in Qarth" is completely empty. However, this looks like a case of the character being genuinely rich, but pretending to be even richer, since he still lives in a lavish palace.
In the second season of Mork and Mindy, Mork comes into Remo and Jeannie's restaurant bragging how he "made millions last night in real estate." Mr. Bickley looks at the "cash" and exclaims, "Wait a minute. This is Monopoly money!" He responds, "Of course. You don't think it would be that useless U.S. currency." Unfortunately, a wannabe gold-digger only overhears that he "made millions." Hilarity Ensues.
The premise of the Bobbie Gentry song Fancy - where a desprate mother living in a shack uses every last cent to buy her eighteen year old daughter a beautiful dress so that she can woo rich gentlemen into giving her an uptown lifestyle. Her Mom dies shortly thereafter, but over fifteen years she comes to own a flat in New York and a mansion in Georgia.
The whole point of Gangnam Style is to mock the people who do this. The title refers to the Gangnam District, a place that is like a Korean Beverly Hills, and the people that hail being from there.
Kisaki actually pulled off posing as one of the richest bandmen and label owners in Japan for a short while, until his signed bands all started wondering where their pay was, and the Japanese counterpart of the Intimidating Revenue Service paid a visit. The result was that Kisaki was actually near-bankrupt and had been evading taxes for years.
In Ace Attorney, Ron DeLite somehow manages to convince his wife that security guards have really good salaries. When he loses his job and can't maintain any salary at all, he resorts to stealing priceless artifacts.
In one episode parodying Seven Up!, Homer pretends to be a millionaire by moving into Mr. Burns's house without his knowledge (Burns is out of town).
In an earlier episode, Homer gather the extended Simpsons family to prove Lisa that they're not all failures. It however turns out most of the men are, including one who pretends to be a millionaire at parties for a living. He then admits he doesn't actually play a millionaire at parties, he just wishes he did.
Subverted in SpongeBob SquarePants when Squilliam Fancyson pretends to be a Mock Millionaire to bait Squidward... only to finally reveal he actually is rich.
In an episode of The Looney Tunes Show, Daffy Duck pretends to be this, among other things, in order to impress his classmates at their high school reunion.
Top Cat once pretended to be a Texan millionaire to out con a couple of con artists who had tricked an immigrant hot dog vendor (who T.C. was apparently going to con himself) into investing in some worthless stock.
Eddy from Ed, Edd, n Eddy has done this several times, such as when he made a video to send to his brother.
In Real Life, especially during the Edwardian Period, social climbers faked their way up using this method. By hanging out with the well-to-do and appearing wealthy they could find a marriage that would usually be outside of their class.
The Fake Sheikh Mazher Mahmood, who uses his disguise to further his nefarious undercover reporting goals.
This was one of the many controversies that surrounded the notorious Fox reality special Who Wants to Marry a Multi-Millionaire? The titular "multi-millionare" Rick Rockwell turned out to have only about $750,000 in liquid assets and a net worth of just over $2 million dollars at the time of the show's airing — a fairly well-off man, but far from the elite member of the One Percent that the show promoted him as. Further digging revealed a history of domestic violence and stalking.
Many families and individuals do, in fact, live well beyond their means in order to create an image of living "the high life." Unfortunately, doing so for even relatively short periods of time tend to lead to massive debt (and possibly bankruptcy). The concept of "keeping up with the Joneses" can lead to this when taken to its logical extremes.
Aristotle Onassis, as a young man trying to make his fortune but still quite broke, stayed in a very expensive hotel. He once borrowed $20 off a friend and bought a packet of cigarettes from the front desk, telling them to "Keep the change". When his friend asked why, he explained that if they thought he wasn't rich they'd ask him to pay his bill.