Where wild minds come to rest
I also love it when two or three characters have a silly or witty banter back and forth. They always manage to make such sharper come-backs then I feel like I ever could, but they came from my imagination so I guess I can... When ever I imagine a particularly funny scene it usually makes me smile or snicker. Which can be a little embarrassing if I'm in a class and happen to be staring intently at a person. I often dream in my bed at night though, so if doesn't often matter.
Hmm... This reminds me of something else I do... If's I'm drawing a character's face, my face often makes the same expression that character is making. I know of other artists who do this as well, so I'm not sure if it's really related.