A duck walks into a store and says "Got any duck food?" The store manager tells the duck, "Get outta here, we don't serve ducks and we don't have any duck food."
The next day the duck is back again asking "Got any duck food?" The store manager says, "I told you yesterday we don't have any duck food!!", and kicks the duck out again.
Third day, same thing. "Got any duck food?" Store manager says "If you come in here asking for duck food again, I'm gonna nail your webbed feet to the floor!!!!"
Sure enough, next day the duck walks in the store and right up to the store manager, "You got any nails???" The store manager says "NO!!!!" The duck then says "Good, you got any duck food????"