Corpse mod allows for devil fruit duping.
To recreate this, you follow these steps:
- Die with a devil fruit in your inventory,
- Find the fruit you died with inside a box, don't open your corpse,
- Consume said found fruit,
- Open your corpse and now you have a duplicate of your fruit
2 or more players can have the same devil fruit with all the abilities, but the check fruit command lists the fruit only being consumed by the last user to eat the duped fruit.