Nine-year-old son:  Wait, ice cream has milk in it?  That means it's good for you, right?

(Nine-year-old son has a new favorite song.  He's been singing it all day.  He's good, but it's getting a little tired.)
Five-year-old daughter:  Would you please stop that??
Nine-year-old son:  Sorry, sorry.
(three minutes later)
Five-year-old daughter:  You know I can still hear your brain singing it, right?