A movement in art started in 1914 during World War 1 where artists displayed their disgust at the propaganda being spread and how the public accepted and promted it. They displayed this disgust through disturbing images, or images that dispict no definite object. Different media maybe also be used to shock the viewer.
Dadaism shocked many and stimulated the viewer to reading the artists statement(often politcal) in their work.
To sneak up to someone in the dark and beat them with a clock, light, fan, or broken shower head. You can also drop these objects on your victem while they are asleep. Feel free to squirt water on them and/or turn on their lights to better surprise them if they've really made you mad. Often screaming the word "dairdair" gives a more creeped out effect.