No Such Thing As A Stupid Question

Everyone has heard that saying "There's no such thing as a stupid question"? Or, "The only stupid question is the one you don't ask".
Yeah. Right.
The longer I teach, the more I'm convinced that there IS indeed such a thing as a stupid question. The stupidest questions I get are the ones that we've already answered as a class, or the ones with answers written on the board. Usually the stupid question comes from one of the students who talks to his neighbor most of the period. The other person who asks stupid questions is the kid who asks one that has already been answered THREE or FOUR times. And this guy doesn't ask it for mere clarification - he is completely unaware that there is anyone else in the room besides him.

I have this other student, who in the middle of class will randomly raise his hand and ask "Is my grade improving?" "Am I missing any assignments?"

A couple of years ago, a student of mine (whom I refer to as Hothouse Flower) raised her hand as I was passing out a quiz. "I have a headache. Do I have to take it?"
"You can go to the nurse if you want. You'll have to make up the quiz later."
"But I don't want to miss class. Can't I just sit here?"
I shook my head No. "If you're here, you might as well take the quiz"
Later that afternoon (thanks to cellphones), I got an email from Hothouse's mom telling me how embarrassed her daughter was that in front of the class, I told her she had to take the quiz. Remember: Hothouse Flower asked in front of the whole class.

Once as I was handing out a study packet (stapled and collated), a student asked "How come you never three-hole-punch things for us?"

And, my personal favorite "Did we do anyting in class yesterday?"