Honestly, there's not too much prep to do. I interviewed last year (the first year they did these) and I was super worried about preparing too but once I actually did them I realized I was panicking for no reason. The best thing you can do is make sure you are confident talking to people in interview situations--practice time management, transitions, eye contact etc. Definitely make sure you are familiar with the format too. It's really different from other kinds of interviews so check them out on MSUs CVM page if you haven't already. I actually liked the MMIs because it's not something you can force or fake. The questions aren't related to your outside knowledge of vet med, or even your own experiences. Every applicant gets the same question and the same amount of time to discuss it. One thing I did was I went to a session about MMIs last year before my interview and they gave us a list of practice questions but I don't think they're doing that this year. The questions were completely varied and may or may not have to do with school or animals. It's impossible to say what kind of questions they will ask. If you're really nervous, find a friend/family member and just talk about a subject, any subject, in a professional manner while timing yourself. Also don't forget that a strong handshake is very important for first impressions!