No need to be nervous - I thought the MWU MMI format was pretty relaxed. There were a couple interviewers that definitely tried to throw curveballs in the form of altered demeanors, which in my opinion was simply to see how we'd react/whether it would throw us off. Don't let it 🙂 There were also multiple interviewers that made it a point to make the applicants feel comfortable/remind them not to be nervous.
If it's a Tuesday or Thursday interview, I'm sure I'll see your group stroll thru while we're in the sim clinic. Best of luck