'Metatheatre' can also include the use of the play within a play, which provides an onstage microcosm of the theatrical situation, and such techniques as the use of parody and burlesque to draw attention to literary or theatrical conventions, and the use of the theatrum mundi trope.
Stuart Davis suggests that "metatheatricality" should be defined by its fundamental effect of destabilizing any sense of realism: ""Metatheatre" is a convenient name for the quality or force in a play which challenges theatre's claim to be simply realistic -- to be nothing but a mirror in which we view the actions and sufferings of characters like ourselves, suspending our disbelief in their reality. Metatheatre begins by sharpening our awareness of the unlikeness of life to dramatic art; it may end by making us aware of life's uncanny likeness to art or illusion. By calling attention to the strangeness, artificiality, illusoriness, or arbitrariness -- in short, the theatricality -- of the life we live, it marks those frames and boundaries that conventional dramatic realism would hide.
Shakespeare employs metatheatrical devices throughout his plays. Some examples include The Taming of the Shrew, Hamlet, A Midsummer Night's Dream, and The Tempest. In each of these plays there is a play or masque presented as part of the larger plot.
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 mentioning of fictional dramatic characters within another play, it would be called a metadramatic moment. Within its original context, however, there is a greater, metatheatrical resonance. Critics assume that the roles in each case were played by the same actor in their original productions by Shakespeare's company; Polonius and Caesar by John Heminges and Hamlet and Brutus by Richard Burbage. Apart from the dramatic linking of the character of Hamlet with the murderer Brutus (and Hamlet as a murderer of Polonius in particular, as will occur in 3.4), the audience's awareness of the actors' identities and previous roles is being triggered.