The TECDP Interview process is very intense to ensure they hire the best. The first round interview (done on campus) involved typical behavioral questions.
The 2nd round, which is on-site in CT, is a day long program done with all TECDP candidates present. It involves another behavioral interview, a group project, a presentation about yourself, a round-table discussion (not part of the interview decision), and a case study - all in front of at least 3 interviewers.
Each part is at least half an hour long (aside from the presentation, which is about 5 minutes), and are all extremely intense. You will feel worn out afterwards, but the experience was entirely worth it.