DAUGHTER: "Why are there two cups in the bathroom?"
ME: "Well, one cup is just for putting water into and the other is only for pouring water out of. So don't pour water from the put cup or put water in the pouring cup."
WIFE: "Also one cup always lies and the other always tells the truth."
ME: "And one is half full and the other is half empty."
WIFE: "And if you find a third cup, that's the friends we made along the way."