I had received an email written in two sentences to provide some days and times for a phone screen. I have responded and had assumed the phone screen was going to take place in the week I was contacted. I didn't get a response back until the following week-- apologizing for not getting back to me sooner and requesting to do the phone screen the next day. I was given a number to dial in and with no heads up with what was coming. I had found out later the no name person who had contacted me was the CEO. The interview ended less than five minutes, which made it not worth wild to get an interview in the first place.
TL;DR:
My impression of the CEO was unprofessional and rude. He wrote to me like I had already knew him. He had to apologize to me twice. He didn't even give me a chance to speak and learn about the position. I was dismissed from the interview after one off answer. I'm not being sensitive but these are telltale signs worth being noted.