Neither as interviewer nor as interviewee but thought I'd share a friend's experience.

My friend's office is small-ish and easily accessible, not a big office tower with security guards and receptionists.

So my friend, who was the CEO and founder of his company, was trying to fill a mid-level position and had a bunch of interviews set up one after another. Just as he was ushering in his next candidate, a golden retriever that had a collar but no leash walked in alongside the candidate.

He was naturally quite bemused but rolled with the punches like a true entrepreneur. Interview begins, dog saunters around, doesn't really bother anyone, lies down under the table for a bit and then leaves the room out the same door it entered.

The interview isn't over yet.

My friend can't take it any more. He likes the candidate and the interview was otherwise normal so now he bursts out, not angrily but very curiously, with, "Why did you think it was normal to bring your dog to an interview?"

The candidate's reply was, "My dog? I thought it was your dog! I wanted to ask you the same question!"

Turns out the dog had just been out for a loiter and decided on a whim to traipse in an opening door.