As a kid my mom used to always say to me "Zui ba bi qi lai" which means close your mouth (although I do believe she had an implied "damn" in front of the word mouth). I would sit at the computer, or dinner, or anywhere, and eventually my mouth would go from shut to open. I call it phantom talking, as displayed above.
sidenote: this one was also taken in a bathroom. i apparently need a private place for these pics.