I've actually had this before. Like there's a topic that I would love to discuss and I imagine that there's an audience right in front of me and I'll keep yapping. Even though I know people aren't there, I still manage to continue and talk.

speaking of talking to oneself, my mean third grade teacher thought that I was talking to myself when I was talking to my neighbor. My neighbor would not defend me and I was pissed because if he had spoken up for me, she would at least know that I'm not crazy and that I was doing nothing unusual.