Penny Among Diamonds

Spencer: "I toldja, its like an turning an old lamp into a chandelier"

—Half & Half

A commoner (or poor person) is thrust into rich culture for whatever reasons, but without becoming rich themselves. Most commonly, it will be a poor student who receives a scholarship to a prestigious school, or a commoner hired to work as a butler/maid for someone rich. Usually the story is portrayed from the view of the commoner. Contrast Rags to Riches, where the commoner becomes rich but may still face taunts and derision from those with OldMoney.

This is a Super-Trope of Princess for a Day and Scholarship Student. Sub-trope of Fish Out of Water. Also see Mock Millionaire.

Examples of Penny Among Diamonds include:

Anime & Manga

He Is My Master: Two sisters are forced to work off a very large debt to a filthy rich kid, and become his maids.
Ouran High School Host Club: Haruhi is a commoner who manages to make it in to a private school, comprising mostly rich folk. Hilarity Ensues.
Hayate the Combat Butler: Hayate is left with a huge debt from his parents, and works to pay it off as a butler under a small rich girl.
Hana Yori Dango.

Film

In Casino Royale, Vesper sizes up James Bond by stating that he doesn't come from money, and was put through school on the charity of others, despite having no money of his own. He neither confirms nor denies this, and his background remains ambiguous.
Metropolitan^[context?]
In The Skulls, the main character has a blue-collar background and is working a succession of odd jobs in order to pay his way through Harvard law school. He sees his association with the eponymous secret society as just one more step up the ladder.
In Miss Pettigrew Lives for a Day, the eponymous Miss Pettigrew gets this treatment, pretending to be an upper-class social secretary in order to find work.

Literature

Jo's Boys (the second sequel to Little Women) musician Nat goes to Europe for school. Due to having wealthy and influential friends everyone thinks that he's wealthy and influential as well. Too bad he's an orphan who spent a number of years as a street musician, and thus has little idea of how to handle money. Cue the nineteenth century version of a Credit Card Plot.
The Great Gatsby is the Trope Codifier, especially since F. Scott Fitzgerald was an example of a Real Life version of this Trope.
- The author himself may count as an example, but none of the characters in this book actually fit. Gatsby himself is Nouveau Riche amongst a bunch of people from Old Money families, while the narrator is personally a bit poor (by upper class standards), but he has only just set out on his own and still has support from his wealthy family.
The Kiki Strike series has Ananka, who subverts this as well as Scholarship Student. At her elite private school, where there are a lot of actual scholarship girls, Ananka is the outsider because one of her relatives left the family money that can only be spent on education and nothing else. So she is neither a scholarship student or rich enough to fit in.
In the Private series, Reed is a Scholarship Student at the elite Easton Academy. Many of the girls hate her for becoming a Billings Girl despite being at the school on scholarship.
Mark Twain's short story "The Million Pound Bank Note" (read it on Wikisource) has the penniless protagonist receive a ₤1,000,000 note issued by the Bank of England. The situation by which he received the note includes a stipulation that he can't spend it (and nobody can make change for it, anyway), so he's still penniless, but he still uses the existence of the note to make his way through London's high society.

Live Action TV

Gilmore Girls: Rori goes to a private high school and Yale thanks to some funding from her grandparents, but her family remains rather poor.
The Nanny: The entire show revolves around Fran Fine leaving Flushing to become the nanny for a rich Broadway producer's children.
The Fresh Prince of Bel-Air revolves entirely around a West-Philadelphia-born-and-raised hoodrat named Will catapulted into his rich Aunt and Uncle's Bel Air community, resulting in many humorous moments as he finds himself at odds with the townspeople and characters, socially and financially.

Tabletop Games

The core book for Hunter: The Vigil mentions that Ashewood Abbey will, once a year, take in a vagrant and give them the good life. If they prove decadent enough, the Abbey extends membership - and, presumably, keeps them buoyed.

Theatre

Any number of variations on Pygmalion (George Bernard Shaw version) fit here.
- Pygmalion (of course)
- My Fair Lady
- Hoi Polloi (by The Three Stooges, no less)
- Trading Places

Video Games

Final Fantasy XII: Vaan and Penelo are poor orphans who go on an adventure with Ashe (The queen of Rabanastre, who's on the run) and Balthier (formerly a Judge of the Arcadian Empire)
Delita starts as this in Final Fantasy Tactics. Arguably Rags to Riches (to tragedy) by the end.

Western Animation

Family Guy: one episode has Chris sent to a prestigious school with some influence from his grandfather, but he is teased as he still doesn't actually have any money. The rest of the family all take on part-time jobs to pay for his tuition.
The Simpsons: When Marge buys a designer dress at a discount and gets invited to a country club.