The Duck

A duck walks into a bar, sits down and asks the bartender for some peanut butter. The bartender replies "I'm sorry we have no peanut butter." The duck leaves. He comes back the next day sits downa and again asks the bartender for peanut butter. The bartender says, "no we dont have any peanut butter, we dont carry peanut butter." The duck leaves. The duck does this two more days, and on the fifth day the bartender is very frustrated with the duck. Once again the duck walks in and asks for peanut butter. The bartender replies, "now I have told you 5 times that we do not have nor do we carry any peanut butter. If you come in and ask again i will nail your bill to the bar." The next day he duck comes in sits down and asks the bartender if he has any nails. The puzzled bartender says "No?" The duck replies, "do you have any peanut butter?"