As Nintendo tries to furiously patch Animal Crossing: New Horizons to nerf certain ways to make money, players continue to find ways around it.
Let’s start with the new duplication method, as there’s a new one every week and it’s easier to break down. As you may remember, folks have been duping items in inventive ways for weeks (Nintendo patched the first widespread method near the game’s launch), but this method involves mail.
Do Whatever Games explains that by using multiple characters on the same Switch, they noticed that they were suspiciously getting extra items in the mail after sending their villagers stuff. They sought to find out how this glitch works, and discovered that it requires two extra characters and two extra controllers (for same-screen multiplayer).
Basically, you need to send items you want to dupe to Player 1, then call them on the phone and quickly swap to Player 1. Player 1 then grabs the presents from the mail and drops them on the ground; swap leaders, then press +/- to “pick residents,” choose Player 2, connect the controllers, then press +/- to end the session. More details are in the video below, where they walk you through it.
Source: Destructoid Players discover a new round of Animal Crossing: New Horizons glitches and exploits