I'm a writer, and I do some of my best thinking just by talking things out. So I'm constantly walking around, talking to myself. I try to quiet down as I pass people on the street, but I have gotten some pretty funny looks from people regardless. No one ever says a word about it though... maybe because they think I'm crazy, I don't know.
And yeah, when I'm bored, I'll start doing goofy shit just to entertain myself. It drove my ex-girlfriend nuts. It's funny how entertaining horribly offensive humor can be when you're bored. And by horribly offensive, I mean puns.