A duck walks into a bar and asks for a peanut butter sandwich.  The bartender tells him they don't have any and the duck leaves.  Next day the duck comes in again asking for a peanut butter sandwich.  Bartender says, "listen here duck - we don't got none and we ain't gonna get none, now get outta here."  Next day, duck comes sauntering in and the little vein in the bartender's head starts pulsing.  Duck asks once more, "can I have a peanut butter sandwich?"  "No we ain't, ya stupid duck, now get outta this bar and if ya ever asks me fer a peanut butter sandwich again I'm gonne nail yer little webbed feet to the floor."

Next day the duck walks in and the bartender looks like he's going to explode.  The duck asks "do you have any nails?"  "What, you stupid duck, no I don't have any nails!" "Oh, in that case... can I have a peanut butter sandwich?"