4 up. They are all workers in a place specified by the instructor – A cake shop, bowling alley, canoe rental, somewhere where they could all be working in the same room. Let them work in silence for a few minutes and discover a dea, mood and backstory for their character.
When it seems like they have a deal, interview them individually about their name, job, aspirations. The interviewee and everyone else should continue to work throughout the interviews. The players can react to others interviews but not try to pull focus.