Satchel Switcheroo

There are three or more identical bags. One bag contains jewels or top secret documents, other bags contain other items of a random nature (and in wildly variable values) and one bag ALWAYS contains underwear.

Through a series of random accidents and deliberate thefts the bags get switched. Repeatedly. The remainder of the story is a form of a farce based on people trying to get the "right" bag. The bags will change hands many times through many different players, and always on camera so that the audience can actually try to play the Shell Game and keep track. Unfortunately, they never actually open the bags to check that the contents are correct until they find themselves in utterly humiliating circumstances. Except for the person with the jewels: chances are they're the unlucky one who lost their underwear. Chances are once they see the jewels they won't really care too much anymore.

The funny pretty much requires at least three bags. If there are only two then the players who are trying to get the bags will easily be able to hunt down the only other bag. But with three or more bags things just get insane.

A common joke in a Screwball Comedy.

There's also a variant where the wrong lunch was grabbed - apparently, in television shows, kids always pack their lunch in a plain brown bag instead of an easily-identified character on a reusable box or bag. Note that in this case three bags are not needed. The humor can come from the child getting raw giblets for lunch instead of their peanut butter and jelly.

Compare Switched At Birth, Shell Game. See also Stolen MacGuffin Reveal.

Comic Books

 * Tintin (Comic Book) was once framed for drug-running this way. The bad guy stole his real suitcase and replaced it with an identical one full of heroin.

Film

 * Blame It on the Bellboy is entirely based on this, with a hitman, a guy considering a real estate purchase, and a big schmuck there for a Medi-Date, each given the wrong envelope at a hotel in Venice. This results in the hitman thinking that he has to kill the real estate buyer ringing the doorbell of  and the schmuck expecting a  to sleep with him.
 * In What's Up Doc, there were four cases, having government papers, jewels, rocks for a scientific presentation, and underwear.
 * In the movie El Mariachi, the bad guys have the titular character mistaken for a hitman with a guitar case full of weapons who is trying to kill their drug lord leader, a situation that is only exacerbated when at one point, the two cases end up switched and the mariachi and the hitman end up with each other's stuff.
 * The fantastic movie Eight Heads in a Duffel Bag embodies this trope.
 * The movie Push does this in a rather unusual way by adding in a bit of precognitive sleight of hand on top of multiple cases.
 * Home Alone 3 starts with two identical shopping bags in an airport. One contains a toy car with a microchip stolen from the Army hidden inside it. The other contains French bread.
 * The ultimate conflict in Police Academy 5 comes about because a group of criminals who have smuggled diamonds into the country have placed the package in which the diamonds are concealed in a bag which is externally identical to Commandant Lassard's luggage, who is taking the same flight as the criminals. They end up claiming the wrong bags when they get to Miami, forcing the villains to try to track down Lassard and reclaim the diamonds.
 * Sylvester Stallone's mobster farce Oscar contains a textbook example: 3 black satchels containing cash, jewels, and the former maid's unmentionables.
 * The Jackie Chan film Legend Of Drunken Master starts with one of these. One package holds a stolen cultural artifact, the other holds a ginseng root that Jackie's master purchased on a shopping trip. The packages get swapped by accident when Jackie tries to smuggle the ginseng past customs.
 * Averted in Fight Club: while the two suitcases are identical, the reason why is something entirely different...

Literature

 * Used in the very first Father Brown story with a package containing a valuable cross..
 * A series of books based on Clue have all of the guests arrive at Mr. Boddy's mansion with identical-looking suitcases. Some contain valuables, and others contain valueless personal items. Given the characters involved, it should be no surprise that the ones who own the cheap items attempt to swap suitcases with the other guests, resulting in one character attempting to steal valuables but winding up with mouthwash.
 * One Lord Peter Wimsey story has a bag of jewellery accidentally swapped for an identical-looking bag containing an actress's severed head.

Live Action TV

 * Done with sausages in Allo Allo - at one time they had a sausage with a stolen painting, a sausage with a fake painting, a sausage with dynamite for La Résistance and an ordinary sausage for Herr Flick's dinner.
 * Used in a more serious vein in Hustle. The grifters often swap out the case full of money at the last second, save for a few episodes where the switch does not go as it should and they lose a lot of money, giving them an incentive to take on a riskier con to make up the cash.
 * Fawlty Towers: Basil has to pick up a roast duck from Andre's restaurant in order to salvage his gourmet night. Unfortunately right next to the duck somebody sets down a trifle with an identical cover.
 * An episode of Will and Grace used the brown paper bag variation of this: the contents being exchanged included Jack's soup, Karen's booze, Rosario's floor polish and Will's sperm sample.

Radio

 * Adventures in Odyssey: It's two identical laptop computers in their identical cases -- one being Whit's, the other being a top secret government computer full of military secrets stolen by Dr. Blackgaard -- that get switched in a hotel shuttle van while Whit and Connie are in Chicago for a conference.
 * In The Goon Show episode "Foiled by President Fred" the payoff involves a red sack and a blue sack. Which sack contains the real money and which contains forged notes? Eccles claims to know, but he's colour-blind. Or is he?

Role Playing Games

 * One D 20 Modern adventure features no fewer than four characters with identical (gaudy and "unusual") bags, each with vitally important and for the most part incriminating contents. Compounding matters are two additional characters who plan to intentionally switch their own (again, identical) bags with someone else's. The Game Master is instructed to treat the adventure as a corporate espionage thriller, so that the players will be surprised when Hilarity Inevitably Ensues.

Theatre

 * In Oscar, there were three cases, having jewelry, cash, and lingerie. Angelo keeps thinking he's finally got the one with something valuable (money or jewels), only circumstances have given him the one with women's underthings... again. And because nearly all comedy protagonists choose the route most designed to embarrass them, he never bothers to check what's inside before dumping it out on the table in front of guests.
 * It ultimately saves him when the police show up to arrest him. Toomey concludes that Snaps is using the bankers to launder money, and has his men look for the black bag as proof (not knowing there's more than one.) Fortunately for Snaps, Nora (the owner of the underthings) comes in and takes the more visible bag of jewels, leaving the bag of underwear for the police. Toomey then opens the bag, thinking it's the final nail in Snaps' coffin, and dumps its contents on the table, right in front of the reporters.
 * The Importance of Being Earnest "A handbag?"

Video Games

 * One of the revelations of The Rashomon in Need for Speed: Carbon is the switching of two bags, one of them with money.

Western Animation

 * Hey Arnold: Arnold, Gerald, and Sid find a shopping bag full of money, and decide to take it to the police station in the morning to collect a reward. But when Arnold arrives with the bag, it's full of birdseed. He tries to explain, "There was this old woman next to me on the bus, and she had pink hair, a peg leg, and one eyebrow. She had a whole bunch of shopping bags just like mine, and she must have taken my bag by mistake." Nobody believes him.