The Melon Drop is a Confidence Game in which the scammer will intentionally bump into the mark and drop a package containing (already broken) glass. He will blame the damage on the clumsiness of the mark, and demand money in compensation.
This con arose (and was named) when con artists discovered that the price of watermelons is quite high in Japan. The scammer (based in another country) would go to a supermarket and buy a cheap watermelon, then go to a tourist attraction and bump into a Japanese tourist. The melon would fall and break, at which point the con man would demand a high price to replace his supposedly expensive melon.
Game and Story Use
- Wait for it. Wait till a PC rolls a critical failure in a public place. Then describe that they bumped into or knocked over some random NPC, and his precious piece of artwork was ruined. Since they just rolled a "1" (or the equivalent in your system of choice), the player will scowl a bit, but probably consent to pay whatever reasonable fee you "improvise" on behalf of the NPC. They may haggle a bit, or complain about their mean GM, but they'll accept this as the consequences of a critical failure. Most players will "do the right thing".
- Later in the campaign, at least a few days or a few sessions later, the same PC is walking in the same neighborhood, and he sees this happen to someone else. The same con man he'd "fumbled into" is carrying the same piece of art. Before the PC can respond, the con artist intentionally bumps into someone and tries to extort money out of them. It doesn't matter how little money the PC was taken for two sessions ago, the chase scene is about to begin.
- Adventurers tend to do a lot of traveling. When in another place, they look "exotic" and might not know that something expensive at home is dirt-cheap here. In other words, they're in the same position as the Japanese tourists.
- Doctor Dastardly has injected his super-plague into a melon, and someone is using it to take advantage of tourists! Can the PCs find the right melon before someone drops it in the middle of the town square?