So I'm sitting here in the computer lab. Since it's exam time right now, no-one is using the labs. In fact aside from me, this lab is empty. 25 computers all sitting empty, and me typing away in a corner.
So this genius pokes his head in through the door, obviously wanting to use a computer, and asks me... "is there a class going on in here?"
Yeah. Sure. There's a real important class going on. Right now. Except I'm the only one that showed up. The teacher is standing right in front of you -- he's just invisible.