Good one, goldie!
A duck walks into a supermarket and asks the manager if they have any duck food. The manager recoils and says, "No we don't have any duck food. And we don't allow ducks in here, so get out!"
The next day, the duck goes back into the supermarket, sees the same manager, and asks, "do you have any duck food?" At this point, the manager is pissed and says, "No! We don't and if you come in here again, I'm going to nail your feet to the floor! So get out and stay out!"
Undeterred, on the third day, the duck goes into the supermarket, sees the manager and asks, "Do you have any nails?" The manager, puzzled, responds, "No. Why?" The duck replies, "Got any duck food?"