Duck Under the Table

Raina asked what was for dinner and I said she'd better go and ask Grandma since she's the cook tonight. This is the conversation that followed:

Raina: "Grandma, what's for dinner?"

Grandma: "I think we might have bread and butter. Would you like bread and butter for dinner?"

Raina: "Yes, I like bread and butter."

Grandpa: "Maybe we could also have duck under the table."

Raina: "What?"

Grandpa: "Duck under the table."

Raina, after a second's thought: "But there's not enough space!"