Early modern theatre
In early modern English theatre, characters often adopt a downstage position in close contact with the audience and comment on the actions of others sarcastically or critically, while the other actors assume the convention that the first remains unheard and unseen while so doing. Following the work of Robert Weimann and others, theatre studies uses the terms locus and platea (relating to "location" and "place", borrowed from medieval theatre) to describe this performance effect—the locus is localised within the drama such that its characters are absorbed in its fiction and unaware of the presence of the audience; while the platea is a neutral space in close contact with the spectators that exists on the boundary between the fiction and the audience's reality.
When the defeated Cleopatra, performed by a boy player in act five of Shakespeare's Antony and Cleopatra, fears her humiliation in the theatres of Rome in plays staged to ridicule her, she says: "And I shall see some squeaking Cleopatra boy my greatness in the posture of a whore". While the actor is not necessarily engaged at this point in the direct address of the audience, the reality of the male performer beneath the female character is openly, and comically, acknowledged (qualifying in important ways, supported further in the scene and the play as a whole, the tragic act of her imminent suicide). Metatheatricality of this kind is found in most plays of that period.
In Hamlet, there occurs the following exchange between Hamlet and Polonius:
Hamlet: ... My lord, you played once i'th'university, you say.
Polonius: That I did my lord, and was accounted a good actor.
Hamlet: And what did you enact?
Polonius: I did enact Julius Caesar. I was killed i'th'Capitol. Brutus killed me.
Hamlet: It was a brute part of him to kill so capital a calf there.
If the only significance of this exchange lay in its reference to characters within another play, it might be called a metadramatic (or "intertextual") moment. Within its original performance context, however, there is a more specific, metatheatrical reference. Historians assume that Hamlet and Polonius were played by the same actors who had played the roles mentioned in Shakespeare's Julius Caesar a year or two earlier on the same stage.[1] Apart from the dramatic linking of the character of Hamlet with the murderer Brutus (foreshadowing Hamlet's murder of Polonius later in the play), the audience's awareness of the identities of the actors and their previous roles is comically referenced.
Another example from Shakespeare is in Act V of A Midsummer Night's Dream. The rude mechanicals present Pyramus and Thisbe to the Athenian nobles, who openly comment on the performance as it unfolds. The storyline of Pyramus and Thisbe closely parallels Lysander and Hermia's story, which suggests theirs could have ended tragically. Then Puck, who has broken the fourth wall multiple times to share asides with the audience, steps outside of the action of the play to address the audience directly. His final speech bids farewell to the audience members and asks them to think of the play as only a dream if it has offended. This relates to the way Bottom rationalizes his experience in the forest as only a dream. These metatheatrical layers suggest that we all inhabit the roles of observer and observed on the worldly stage and that it's possible to dismiss strange experiences as dreams.
Modern theatre
The fourth wall
In the modern era, the rise of realism and naturalism led to the development of a performance convention known as the "fourth wall". The metaphor suggests a relationship to the mise-en-scène behind a proscenium arch. When a scene is set indoors and three of the walls of its room are presented onstage, the "fourth" of them would run along the line dividing the room from the auditorium (technically called the "proscenium"). The fourth wall is thus an invisible, imagined wall that separates the actors from the audience. While the audience can see through this "wall", the convention assumes, the actors act as if they cannot. In this sense, the "fourth wall" is a convention of acting, rather than of set design. It can be created regardless of the presence of any actual walls in the set, or the physical arrangement of the theatre building or performance space, or the actors' distance from or proximity to the audience.
"Breaking the fourth wall" is any instance in which this performance convention, having been adopted more generally in the drama, is disregarded. The temporary suspension of the convention in this way draws attention to its use in the rest of the performance. This act of drawing attention to a play's performance conventions is metatheatrical.
A similar effect of metareference is achieved when the performance convention of avoiding direct contact with the camera, generally used by actors in a television drama or film, is temporarily suspended. The phrase "breaking the fourth wall" is used to describe such effects in those media.
Modernism
Instances of metatheatricality other than "breaking the fourth wall" occur in plays by many of the realist playwrights, including Henrik Ibsen, August Strindberg, and Anton Chekhov. As with modernism more generally, metareference in the form of metatheatricality comes to play a far more central and significant role in the modernist theatre, particularly in the work of Bertolt Brecht, Vsevolod Meyerhold, Luigi Pirandello, Thornton Wilder, Samuel Beckett, and many others.
In more recent times, With the People from the Bridge by Dimitris Lyacos employs metatheatrical techniques whereby a makeshift play centered on the vampire legend is viewed from the angle of a spectator who records in his diary the setting and preparations as well as the sequence of the actors' soliloquies interspersed with personal notes on the development of the performance.