Anybody want to hear a joke?

I'm not sure why I think this joke is funny, but when I heard it a long time ago, I laughed really hard. Then someone emailed it to my mom a couple of weeks ago and I still thought it was funny. Here goes:

A duck walks into a store , hops up on the counter and ask the clerk " hey, you got any grapes?

The clerk say's No- I don't have any grapes, and we don't do business with ducks . Now scram.

The next day the duck goes back into the same store, hops up on the counter and ask "got any grapes?

The clerk say's I told you yesterday, we don't have grapes, and we don't serve ducks, now get out of here.

The next day, the duck goes in the store, hops up on the counter and says to the clerk " got any grapes?

The clerk says" Look Duck, I've told you for the last three days, we don't have grapes and we don't do business with ducks. Now if you come in here one more time I'm gonna nail your flat webbed feet to that counter.

The next day the duck walks into the store , hops up on the counter and say's" Have you got any nails?"

The startled clerk say's No.

The duck say's " Good, Got Any Grapes."