The interview was very casual, the faculty interview was not typical. There were no set questions, I was simply told "tell me about yourself" the student interview was similar, tell me about yourself, no questions that you expect, the "tell me about a tough decision you have made", or "what would you do if you did not get accepted this year?". The interview as I interpreted it is important as I can tell you my GPA was very mediocre, (granted PCAT was very good) so I imagine that the interview carried me. The student mingling time seems to be your chance to shine, to show how you are outgoing and will act as a pharmacist. I encourage you to engage all the people there students and faculty alike. Make sure you know what Mercer offers and talk up the aspects that brought you to the school in the first place.
Good luck to you, the campus is attractive and the staff kind and courteous.