This duck walks into a bar, and asks the bartender, “Do you have any grapes"? 

The bartender says, "No we only sell beer here". The duck leaves. 

The next day the duck walks back into the bar and asks the bartender, "Do you have any grapes"? 

The bartender says, "No I told you we only sell beer, and if you ask me again I’m going to nail your beak to the bar.” So the duck leaves. 

The next day the duck walks back into the bar, and asks the bartender “Do you have any nails"? The bartender says "no". 

Ahhh okey !! Do you have any grapes"?