He used to pop every now and again where I worked a few years ago. First time I was so engrossed in what I was doing I didn't see him standing at the end of my cubicle, gave me an absolute fright. Then I had no idea of what I was supposed to say or do, did I have to curtesy or how to acknowledge him respectfully. The girls I worked with were in hysterics as I just went pale and said g'day. Absolutely mortified!