If you drop an item (or a stack of items) and switch to a different hotbar slot at the same time, you appear to drop the item (or stack) that you pressed 'q' on, but it doesn't actually duplicate. You can pick the item(s) up again, and nothing appears to change. If you click on the hotbar slot in your inventory that you switched to, the item(s) that were there will reappear. The dropped items still emit a sound when picked up.     Note: This only works in survival mode, it doesn't work in creative.