Earlier quoted context omitted.
Ego issues sometimes apply to the interviewee as well. I once had to interview someone that clearly thought the interview process was beneath them. This person answered every question as if it was a stupid endeavor and we should just hire them since it was just obvious how great they were.
What would have been a way to find out s/he had that mindset, before having the interview?
All jokes aside he was not foaming at the mouth or unpleasant when we first started the meeting, and I'm not the quickest one to pick up on subtle body language cues. So your guess is as good as mine.