One person leads and selects the order of participants. Then the first person says one line like" Once upon a time in Silk board" then the second person says "there was a traffic jam" and then the third person adds one line and so on and on. This exercise ends up being hilarious and you can control the time and the rounds and give a structure to it as the intro, plot 1, plot 2, plot 3... and ending. The lead must control the story and keep things from going too off topic or become repetitive.