What's weird? I don't even know anymore.

At Beat practice tonight we attempted to learn this song on a whimsical whim. How it came up? It just started playing in our practice. I didn't bring it up. I have no idea how or why this song started playing, but I just followed along once it did.
The funny thing - It has been rolling around in my subconscious for a week or so. It is one of those songs that gets half stuck in your head somehow, someone threw a slice of the record and it penetrated my skull, and you wonder what song that is, or you wonder how it all goes, or you wonder who it is written by or something- you can hear a distinct guitar tone or drum pattern or set of vocal pipes that you know who they belong to but just can't identify...your mind gives you bits and pieces and they just roll around in your dome like a broken stain glass window and you can't really tell what it going on. Then someone gets out the glue and puts the pieces together and you realize, "Oh shit, that is it, that is the song that has been in my head all week." And you realize that while you are playing it - after the first verse, even though you don't know how to play it or never did. It's like a rock and roll exorcism.
Sometimes things are strange like that, but only in hind sight. With out thinking too hard it seems so natural that it isn't weird at all.