entertainmentjunkie I think what shocked me most about Super Saturday was that everything leading up to your interview was designed to calm you down and get you relaxed before your interview.
If you've been to an open house, Super Saturday is reminiscent of that - networking and refreshments in that main foyer area, and almost feeling like you're pre-interviewing when sharing your background with other students.
What's nice about it though is that by the time you get to the interview, even if you arrived only 30 minutes before, you've already had a "warm up" so to speak so you're not going into the interview cold.
Interviews are done by a mixture of admissions staff, some alumni, but mainly second year students. They almost exclusively go through your resume (90% of the interview is resume based) so just be prepared to speak on every stop on your resume and what you learned from it, or what you contributed.
Because it's FEMBA, they'll want to know how thoughtful you've been about planning the commute (if you have one) and time commitments since apparently it's a hard adjustment for most people when they start the program.
One last thing, I've noticed that UCLA tried to pair applicants with an interviewer whose MBA focus closely mirrors what you've expressed on your application. All in all, just be yourself and it'll be a pretty chill experience.