Dreams again: I awoke one morning from troubling dreams to find myself transformed in my bed into a... No, wait, that was another night. The one I'm thinking of now, I was having dreams where I had no idea who I was. I awoke having to urinate, and staggered off to the bathroom. Once I was in the act, my identity crisis swiftly resolved.
At that moment, I realized a deep philosophical truth: I pee, therefore I'm me.