It looks like they’re trying to communicate by yelling into each other’s mouths.
Arthur: Karen, were you doing that in the mirror all of yesterday lunchtime?
Karen: Pretty much. To The White Stripes.
Karen: (to Arhtur) Shut your face. (to Matt) What vegetable would you be? A pepper? Why?
Matt: Because they’re super-food, and they’re red, and they’re crunchy, and you can cook them, or you can just have them fresh.