Duck : Do you have any duck food?

Storekeeper: No

Duck : Do you have any duck food?

Storekeeper : No, we have no duck food

Duck : Do you have any duck food?

Storekeeper : NO!!  We do not have any duck food!!

Duck : Do you have any duck food?

Storekeeper : NO!!  WE DO NOT HAVE ANY DUCK FOOD!!  And if you ask me that one more time I'm gonna nail your little webbed feet to the floor!

Duck : <thinks> Do you have any nails?

Storekeeper: <sigh> No....

Duck : Do you have any duck food?