Never leave your computer alone with bored people.
One of my mates isn't the most intelligent of men. He also frequently made the mistake of leaving his computer unattended while he went off to poo. Of course, the first thing I did was change his desktop background into a screenshot of an open firefox window proudly displaying goatse. He spent about fifteen minutes desperately trying to close the "window," while everyone giggled at him.
Still makes me laugh like a drain, and this was a couple of years ago.

I also nearly convinced him owls were a species of plant. "You're joking, right?" Good times, good times.
(TheWonderfulWombat It came to me in a dream., Mon 21 Sep 2009, 2:22, Reply)