LOL. I totally do that too, and I'm always surprised when I suddenly remember some obscure fact.

I was playing Trivial Pursuit with my aunt, and one of the questions was "What is the last Grand Duchy in Europe?" I said "Luxembourg!" before she'd even finished asking the question. I have no idea how I knew that - I can't remember ever having leaned anything about Luxembourg, in school or outside of it, but the answer just jumped out of my mouth without me having to think about it.