The Mute Button
Idea for an activity: in trios, one player is the couch potato, the other two are actors in a TV show. The actors improvise a dialogue. At any time, the couch potato can say, "mute!" as if hitting the mute button on a remote control. When s/he does that, the players continue their dialogue without any sound.
The players have to pay attention so that when the couch potato turns off the mute, they have something to say.