Got called for the interview in DC. Walked in to the embassy about 20 minutes early. There was a waiting room with a previous JET teacher and a video about the JET experience. The woman I talked to was very nice and personable, willing to answer any question. Then I was led to an interview room with three interviewers. Two women who had done JET, one Japanese man who worked for the embassy. Basic question - why JET, what skills do you have that would help you, talk about when you've taught children, challenges you faced (I did volunteering with teaching kids music). Lots of questions based on my resume/application/personal statement. Also had to do a brief section in Japanese (because I speak it) talking to the Japanese man and then reading a selection and answering questions in Japanese about it.

You will be interviewed by a panel of around 3 people. One person was kind of the "bad cop" who would ask tough questions, so be prepared for that. The main interviewer will ask you about your professional and educational background, and be sure to highlight any activities that involve cultural exchange or involvment in the Japanese community, rather than strictly interest in Japan. Another interviewer will try asking you questions in Japanese, but this is usually only bonus points for the interview.