A duck walks into a store and asks the cashier, “Do you have any grapes?”
The cashier says, “No, we don’t sell grapes.”
The next day, the duck returns. “Do you have any grapes?”
The cashier, annoyed, says, “I told you, we don’t sell grapes!”
The day after, the duck comes back again. “Do you have any grapes?”
The cashier yells, “If you come back and ask for grapes one more time, I’m going to nail your beak to the floor!”
The next day, the duck walks in and asks, “Do you have any nails?”
The cashier sighs. “No, we don’t have any nails.”
The duck grins. “Good. Do you have any grapes?”