Kotaro in Papuwa. Keeping in mind that this Dude Looks Like a Lady (to the point that some viewers have refused to believe that he's a boy), he occasionally has fantasies along these lines... which involve him living in a castle in an elaborate dress, like a princess. As it happens, his family actually is rather wealthy, he just doesn't know it.
What would Lawrence from Office Space do if he were a rich man? "...two chicks at the same time, man." What would Peter Gibbons Do? "Nothing."
Mamma Mia! has the heroine and her friends sing 'Money, Money, Money' by ABBA while having a fantasy about lying around on a private yacht being waited on by handsome sailors.
Played with in High Society, where two reporters, while taking in the luxurious home of the high society family they're writing a story about, sing "Who Wants To Be A Millionaire!" ("I Don't!"), listing in the song all the luxuries they could afford if they were rich, and for each one, claiming not to want it. By their expressions and the effort they put into the song, it's implied to be a case of Sour Grapes, however.
At the start of the remake of The Italian Job, the robbers fantasize about what each will do with his share of the loot. Lyle wants an expensive stereo set-up (speakers so loud they blow a woman's clothes off, literally), Handsome Rob wants a car, and Left Ear wants a mansion with a room just for his shoes. You get to see their dreams come true at the very end of the film, once they get the loot back from Steve who, with no ideas of his own, stole each of theirs along with the money.
Willy Krueger in Mr. Krueger's Christmas frequently has these fantasies, distracting him from his lonely life as a custodian at an apartment building.
The Twelve Chairs / The Little Golden Calf: This is Ostap Bender's motivation in both books he appears in. The third and final part of The Little Golden Calf is actually a deconstruction: even after Bender gets his long-desired wealth, it turns out to be near-useless in the Soviet Union, where he can't be openly rich, while goods and services are mostly gained for government favors, not money.
Dorothy Parker wrote a short story called "The Standard of Living" about two girls who like to play "If you had a million dollars..." It ends with them going to a jeweler's to look at a necklace, guessing that it costs a thousand dollars, or maybe ten thousand.... The jeweler tells them it's $250,000. As they walk away, one of them asks the other what she would do if, say, someone died and left her ten million dollars.
In the treasure hunt episode, everyone in the main cast has one. Zack imagines that he's married to Maddie and has his own private arcade, Cody imagines winning the Nobel Prize in every subject (plus baking), Maddie imagines becoming the president, Esteban imagines becoming manager of the Tipton Hotel and making London a bellhop, and London... imagines it to be just like her life is right now, as she's already filthy rich.
When the Scrubs gang enters the lottery, they imagine what they'd do with millions of dollars. This provides a few opportunities for other characters to do JD's "imagine for a bit, oblivious to the world, then come back with a bizarre statement" thing. Dr. Cox imagines putting Jordan into a box. "I gotta call my glass guy."
The show also features the Barenaked Ladies song in the page quote.
Jackie has one of these in the That '70s Show episode when she find out that Hyde has potential, judging by his SAT score. "Now we don't have to be poor!" After, Hyde remarks "Was there a string quartet? If we're rich, we're getting Led Zepplin or something" and Fez complaining about always being the butler/servant in their fantasies.
Only Fools And Horses is made of this trope. Every single business deal Del enters into is part of his get-rich plan. He is constantly saying "This time next year, we'll be millionaires!" He and Rodney actually sing the song in the hilarious episode "And the Unlucky Winner Is ...", when they thought they'd won a million pasetas. Of course, because they told all those lies, they are unable to collect the money.
In one episode of Little House on the Prairie , Laura and one of her schoolmates discover what they believe to be gold in a nearby stream, and secretly begin sifting it out into a wheelbarrel. In the days it takes to do this, Laura has ongoing dreams of her and her family being gorgeously dressed while everyone else in town looks on enviously while covered in filth and rags. Of course, the 'gold' turns out to be pyrite.
One musical number in The Muppet Show inverts this with "What Do the Simple Folk Do?", which features a lord and lady wondering about the peasantry. At the end, they decide that the peasants wonder what the nobles do.
The Trope Namer is a song from Fiddler on the Roof which also toys with it. The only real thing he shows humbleness towards is that he would be able to work less so he could spend more time in Synagogue praying, which points up why he is willing to have his daughters tutored.
Perchik: Money is the world's curse! Tevye: May God smite me with it. And may I never recover!
Higher And Higher: The song "Disgustingly Rich" from the obscure Rodgers and Hart musical.
In The MusicalIn the Heights, there's a song called "$96,000", which is all the characters fantasizing in counterpoint about what they'd do if they were the ones with the winning lottery ticket.
Allegro: The ironically titled song "Money Isn't Everything" from Rodgers and Hammerstein's play.
Twelfth Night: Malvolio has quite the indulgent one about marrying the rich Olivia.
Ben Jonson's "The Alchemist" has many characters fantasizing about what they'd do with the Philosopher's Stone. Sir Epicure Mammon gets the longest speech; he plans on feasting on exotic delicacies like quail tongue and lampreys, and he'd be so rich that feather mattresses would be too coarse—he'd have to have air...he'd set up a system of aqueducts to carry milk and rose-water to everyone...
Upon hearing of an opportunity to "become a moderately wealthy man", Homer imagines himself rolling in a small pile of money and shouting, "I'm sort of rich! I can rent anything I want!"
Making $11 on the stock market, and fantasizing about getting a carwash.
One of his odder ideas was that winning the lottery would let him become a 100-foot tall gold-plated demigod.
He imagined himself living in a house made of pearls and losing his teeth to his breakfast, a bowl of pearls.
He had a fantasy of having his own recording studio.
He imagines what his life would be like if he robbed the Kwik-E-Mart, and sees himself sitting in a rocking chair outside a huge mansion, wearing a top hat, smoking cigars, monocle and a sash saying "Senator", while Marge go-go dances in a swimsuit next to him. By the time he decides he will rob the place, he has already done his shopping and is driving away from it.
After sinking his money into a doomed stock, he assures the broker that he knows the risks... as he imagines himself in a Broadway revue, singing "We're in the Money" with a group of scantily-clad female dancers as the curtains open to reveal a giant gorilla roaring and holding fistfuls of cash.
Homer: You heard the monkey, make the trade.
"With ten thousand dollars we'd be millionaires! We could buy all kinds of useful things, like... love!"
Bart got in on this once. After being told of winning $500 in a lawsuit, he imagines hitting Vegas, betting it all on roulette. And loses. He still chuckles after the dream plays out.
Lisa had one, briefly—when the FBI informed the family that Homer had stolen the trillion-dollar bill, Marge says it's going straight in the college fund. Lisa—this was before much of her development into the hippie of the family—yells "who needs college?! We're trillionaires! Let's buy dune buggies!"
One episode has Bart dreaming that he is a rich and famous rock star. Of course, his dream just shows him insulting his fans onstage, throwing a liquor bottle at Milhouse after being criticized for his spoiled, hedonistic attitude, and (strangely) having a British accent.
Family Guy: Peter Griffin, though he usually think of some ridiculous thing he would spend the money on. In fact, in the very first episode, a computer error at the welfare office resulted in them getting a huge check from the government, which he used in part to build a moat around the house (to keep the Black Knight away, of course).
Done in Xiaolin Showdown in an illusion made by Wuya to help her We Can Rule Together Speech. Raimundo sees himself in a mansion with his own video arcade, a skateboard park, and a butler serving him pizza and soda — basically, anything and everything he wants or could ever want... She does however give him these things later after his Face-Heel Turn, though.
In Jimmy Neutron, the kids ponder what they will do with the money they'll get after they acquire Astro Rubies.
Radcliffe in Pocahontas has one when he imagines how rich he will be once he finds gold in the New World.
Beavis and Butt-Head: Monsieurs Butt-head and Beavis do this when they hear that there's a reward being offered for their missing friend. Butt-head imagines laying next to a pool while a girl brings him a drink. Beavis does the same thing — except his girl brings him a detonation plunger.
When they considered what they might get for copying David Letterman, they just imagined sitting on the couch with piles of cash and some chicks.
Futurama: Mom started to wonder about what she would do if she had all the money of the world but stopped when she remembered she does have it.
Recess: In one episode, the gang finds a hundred dollar bill, and each of them fantasizes what they'd do with it. All of their fantasies include a jetpack.
On The Wild Thornberrys, Eliza told Darwin she'd buy, among other things, a swimming pool full of chocolate. When Darwin asked whether she could eat it all, she said, "No, and I don't care!"
In King of the Hill, Bobby comes to the mistaken assumption that his father is a millionare* He overheard Hank talking about his $1000 bonus, assumed it was his daily paycheck, and then added it up through bad math. What follows is an Imagine Spot where the Hills are portrayed as a combination rich hip-hop artists and Scrooge McDuck, with a pair of white tigers, a personal helicopter, and a dollar sign-shaped swimming pool.
Who hasn't fantasized about what they would do if they won the lottery?
Glam Rap runs on this trope. Especially since most such rappers aren'trich at all, or get their money through some non-music means (such as launching a clothing line.)