Minecraft wiki entry for Block_and_item_duplication, associated text: This method exploits the fact that zombies can transform into drowned while they are dying. If you coax a zombie to pick up an item by throwing one at it and then kill it right at the moment that it converts to a drowned, the zombie will die and drop what it was holding but the newly spawned drowned will be holding a duplicate of the item. This can also work with husks transforming into zombies.