"Tell Me About When You Are Lazy."
That's not a bad request of job applicants. Even if you gave them advance notice, the discussion could be profitable. Discovering how they define the request would be revealing and it probably wouldn't be hard to spot self-serving versus candid replies.
It's not a question of whether people will goof-off or day-dream, but a question of how often and when. You want to know their priorities and their proclivities. Do they know when to back-off? Are they capable of relaxing? We usually hear more about the first than the second.