What Does ____ Say?

So, I was quizzing the kiddos a few days ago on the sounds different things make.  We started with animals (What does the cow say?), and then moved onto different types of vehicles (What does the train say?).  Both kiddos were having fun with this and so I kept going, until I ended up with this gem:

Me: What does Mommy say?
Little Brother shakes his finger in my face*: NO NO NO!!

*For the record, I don't remember ever shaking my finger at the kiddos, but I do tell Little Brother "no no no!".  Apparently a lot.