Answer:
What can you blow up and keep intact?
When one does not know what it is, then it is something; but when one knows what it is, then it is nothing.
4 rubber ducks were floating in the bathtub, 2 floated away and 2 drowned. How many ducks are still alive?
I always run but never walk, often murmur, never talk, have a bed but never sleep, have a mouth but never eat. Who am I?
Never swallowed but certainly chewed, tossed in the mouth but it is not food. What is it?
I am your mother's brother's only brother in law. Who am I?