From Wikipedia, the free encyclopedia:
"'Happenings' are a form of participatory new media art, emphasizing an interaction between the performer and the audience."
"Happenings take place anywhere, from basements to studio lofts and even street alley ways..."
An example of a modern happening would be the popular interactive comedy "Shear Madness", in which, after an introductory sequence that leads up to an unseen murder, the audience takes part in questioning the actors and ultimately takes a vote to determine "whodunnit". Whomever the audience declares is the murderer assumes the role of murderer, confessing to the crime and explaining how it was perpetrated as if it were a written role (when in truth any of the actors could have been the murderer, by how the audience voted). The show is based heavily in improvisation, and is defined primarily by the audience.