Happening
An unpredictable situation, performance or a series of events that often tries (and succeeds) to cause the viewer’s participation. Appeared and developed in the late 1950’s and early 1960’s in the United States and was aimed at breaking the barrier between the "art" and the "life". The eighteen happenings in the six parts of A. Caprow (1959) and the Days Shop (1962) of Claes Oldenburg are some of the famous and remarkable samples of the species.