I don't think this is done all the time, but a recruiter was hired to find an external candidate back when I was hired. I was interviewed by him and completed several tests for him. I then met the supervisor of the job privately, one-on-one; again, I don't think this is usual procedure, but she really wanted to be certain of a good "fit" between herself and the candidate due to the close working relationship. Then I had a panel interview: I think there were 5 people present asking me questions.