You probably know mine was in sleep medicine but I think I can give you general comments that will hold true no matter what.
First, fellowship interviews are definitely more social and "getting acquainted." I was never asked a pimp question, and was only asked personal (appropriate) stuff like why did I consider their program, what got me interested in sleep medicine, was I interested in academics, etc. These questions were totally appropriate and were honest probing about my intentions and to legitimately judge my fit with particular departments/divisions. I was asked about a couple of things on my personal interest statements, and a couple of simple questions about my "research" choices (like why I picked what I picked...not fine points about the methodology).
On the whole, the fellowship interviews were a lot of fun and I remember them (and the entire fellowship year) as the very best part of all of my medical education from the M1 year through all of residency. Which I suppose is true for everyone. Being a fellow is awesome. You still have attendings who are ultimately responsible for everything, and you are freed from the medical student/resident work force. You are actually able to go and read journal articles and textbooks at whim, and see patients that are 99% of the time appropriate for you clinic. I loved every minute of it.
My advice is take every interview seriously, and play to win every single time at every single location (no matter the program's status on your wish list). If you aren't willing to move somewhere, then why interview? Be professional, be on time, be friendly, be articulate, and be fun. Just like any job interview. Don't be afraid to sell yourself. You think you'd be better than the other qualified applicants? Tell them why. Want to live in another state when you're done? Tell them where and why. It's okay. People will respect the truth. I always thought it went without saying, but don't be afraid to be honest.
