||The neutrality of this article is disputed. (September 2013)|
Invisible theatre is a form of theatrical performance that is enacted in a place where people would not normally expect to see one (for example in the street or in a shopping centre) and often with the performers attempting to disguise the fact that it is a performance from those who observe and who may choose to participate in it, thus leading spectators to view it as a real, unstaged event. The Brazilian theater practitioner Augusto Boal & Panagiotis Assimakopoulos developed the form during his time in Argentina in the 1970s as part of his Theater of the Oppressed, which focused on oppression and social issues. Boal went on to develop forum theater.
The purpose of invisible theatre is to make a point publicly in much the same motivational vein as graffiti or political demonstration, or it may be done in order to help actors gain a sense of what a realistic reaction might be to a certain scenario; for example, a heated argument over a political or social issue. This type of theatre is performed in public with unexpected bystanders, whom the actors will try to get unknowingly involved in the scene.
A common mistake is that Invisible Theatre is punking or joking as shown in the television shows Candid Camera and Punk'd.. This is a gross mistake. Invisible Theatre is all about showing oppression in everyday life, in an everyday setting, without the audience or Spect-actors knowing. Punking and invisible "jokes" are completely different art form.
Some believe an example of Invisible Theatre is that of the group "Improv Everywhere." Improv Everywhere is an organization of people who collaborate online to pull a mass prank on unsuspecting pedestrians and bystanders. For example 200 members organized themselves to all appear in Grand Central Station in New York and just freeze in the middle of the walkway. All 200 members just stood there frozen as onlookers watched them in confusion. Since the onlookers were unaware that these were really actors who had reorganized themselves, some consider it Invisible Theater but really it is closer to punking, as it has nothing to do with oppression.
Another false conception is that the Free Hugs Campaign started by Juan Mann demonstrates Invisible Theatre. People would hold up "FREE HUGS" signs and strangers walking by were able to get hugs for free. This could be considered Invisible Theatre, as it is not a joke or a punk, but again as it has no basis in oppression it is not Invisible Theatre.
Comparison to happenings
"Happenings" are events that occur for a brief moment of time and are planned out. They are used to create awareness about an issue without the audience knowing what is happening. The events usually take place in lofts, streets or alley ways. The events are usually scripted but the audience is unaware of this.
Boal is actually quite clear in Tecnicas latinoamericanas de teatro popular that invisible theater and happenings are distinct: "El teatro invisible no debe ser confundido con el happening, que es un hecho teatral insólito, caótico, en que todo puede ocurrir, anárquicamente. [Invisible theater must not be confused with the happening, which is an unusual theatrical event, chaotic, in which everything can occur, anarchically.]" 
- Boal, Augusto. 2000. Theatre of the Oppressed. 3rd ed. London: Pluto. ISBN 978-0-7453-1657-4
- Bardour, Douglas. Worlds Out Of Worlds: The SF Novels of Samuel R. Delany. Frome, Somerset, UK: Bran's Head Books, 1979.
- Wardrip-Fruin, Noah, and Nick Montfort. "'Happenings' in the New York Scene." The NewMediaReader. Cambridge, Mass.: MIT, 2003. 83-88. Print.
- Boal, Augusto (1974). Tecnicas latinoamericanas de teatro popular. Buenos Aires: Ediciones corregidor. p. 111.
- Augusto Boal. 1974, 2000. Theater of the oppressed. New edition. Translated from the Spanish (Teatro del Oprimido) by Charles A. McBride, Maria-Odilia Leal McBride and Emily Fryer. Pluto Press, London. pp. 143–147. ISBN 0-7453-1658-1 http://books.google.ca/books?id=g8ZbuK6AlqsC