Ahhhhh, so somebody had poured a load of graphite down the vents and stood back and waited. Seen that done in the monitor and PSU, most amusing.
My favourite used to be changing the orientation of the PFYs mouse, it used to be set to 180% and if you change it by around 5 % a day they adapt and get on with things. When you have got them at the apogee and they are working in an impossible contorted position you then switch it back to normal in one fell swoop.
It gets them every time, "it was alright yesterday" they say when in reality they had to twist their hand back on to the wrist and twist the shoulder and arm to use it.