If you give mouse cookie, he'll probably ask for glass of milk. Then, he will probably need straw for milk. His whiskers will be dirty, so he will ask for napkin. Napkin will be dirty, so he'll need to throw it away. He'll see that garbage is full, so he'll offer to take it out. His hands will be dirty, so he'll want to wash them in sink.
He'll probably ask for towel. Towel will remind him of his blanket and his bed. Then, he'll ask for blanket to take nap. While he takes nap, you'll probably want to remove mouse from your house. Otherwise, he will ask for cookie all over again.
whiskers (n.) – coarse long hair around the mouth of a mouse
Adapted from"If You Give a Mouse a Cookie." Numeroff, Laura Joffe. Link
Also see "If You Give a Moose a Muffin", "If You Give a Cat a Cupcake" and so on.