I wouldn't say that any specific question was hard or unexpected, but what I will say is that every interview was very thorough. I was asked questions about college and every job since. Not only what I liked or didn't like about each one, but what I learned (good and bad) and how I can apply that to future success. They want to make sure they are getting someone who isn't afraid to admit when they make a mistake; someone who can learn and make something better every chance they get.
