An elementary or intermediate level exercise/game. It´s pretty hard to find exercises that keep low level students talking for a whole hour(even in a controlled situation) while keeping them thoroughly amused. This does the trick. Also just upgrade the questions & use the same activity for all level classes/groups. I actually also use this after I have introduced questions without auxiliaries as it has a mix of both question forms. Should keep a class happy & laughing & debating for the entire lesson. Otherwise just use it to give yourself & the kids as a break from normal lessons.