Def.: When, while watching/listening to/reading/dealing with a thing, a voice in your head — not your primary train of thought — suddenly starts offering ridiculous input into the situation. Sometimes takes the form of a “what would such and such say about this thing.”
Usage: The most ridiculous kind of backseat commentary is when you start thinking about how fictional characters would react to seeing the actors that play their friends or enemies in other roles.
–your fangirl heroine.