I worked in a call centre breifly many years ago, and we decided to play a trick on one particularly dumb (blonde) colleague. (yes, she was hot though...)

We did the old Ctrl+Alt+down trick as above to rotate the layout of the screen so it was upside down.

We then turned the physical monitor upside down so that the screen orientation was the right way up.


She came back to her desk and saw her monitor upside down told us all we were "silly boys" and picked it up and righted it. Looked confused for a minute as the view was now upside down, and then picked it up and upended it again, then again and again and again until she started to get frustrated and tired and ended up dropping it...

HILARIOUS!