Encounter 1:

I was walking back to my office and heard this deep voice behind me say ‘thesis thesis’, and when I turned around, there was nobody there.   My supervisor had evidently ducked into an office.

Encounter 2:

I was standing in the corridor talking to a couple of colleagues when my supervisor walked past in a rush and asked ‘Sarah, what are the three magic letters?’

My colleagues looked at me bemused as I called to his now disappearing back, ‘P H D?’.    ‘Exactly’, came the faint reply from down the stairs.

[And isn't it telling that I don't actually have a category related to my PhD on this site?]