Were you expecting a lullabye?

Whenever I get really tired, and I start to think about how wonderful sleep is, a little snippet of song goes through my head. It is often one of the last things that I think to myself. I'm not sure exactly why my brain chooses this particular little melody line to segue into dreamland, but almost every night, just when I'm about to drift off, I hear in my head: "I neeeeeed to sleeeeeeep.......in a van down by the riverrr."