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The Impossible Quiz
Looking through all the rubbish I've bookmarked I found this:
http://www.notdoppler.com/theimpossiblequiz.php
Yeah, almost certainly been posted before but I can't remember it. I have no idea why some of the answers are the right ones. My favourite question is 18.
Note: best mute the sound, if the questions don't drive you mental the music will.