When Sir Philip Sidney first mentions the theatre in A Defence of Poetry he asks rhetorically "What child is there, that, coming to a play, and seeing Thebes written in great letters upon an old door, doth believe that it is Thebes?" (p. 53). This allusion to the generally accepted fictional status of the world of the theatre is later qualified when he advocates adhering to the classical unities in order to maintain the dramatic illusion. The popular theatre of the day "where you shall have Asia of the one side, and Afric of the other that the player when he cometh in, must ever begin with telling where he is, or else the tale will not be conceived" (p. 65) is criticised for putting too much strain on the audience's imagination, thereby weakening the plausibility and completeness of the imagined play world. In A Midsummer Night's Dream, Shakespeare's mechanicals go to great pains to destroy the dramatic illusion, to lay bare the artifice of what Theseus calls a "palpable-gross" construct. The play of Pyramus and Thisbe, Shakespeare's comic anatomy of sixteenth century stagecraft, takes its onstage and off-stage audiences behind the scenes to explore the poet-dramatists's art through the lens of parody.
Parody can break down its hypotexts into something like nonsense ("the silliest stuff" in Hippolyta's terms) or, conversely, map out the boundaries of a more meaningful text. The play-within-a play structure lends itself naturally to burlesque since it allows the playwright to display the stigmatised practice in a relatively secure manner. The Pyramus and Thisbe play is held up as a critical mirror to the theatrical competence of sixteenth century playmakers, players and audiences. It disfigures the fundamentals of stagecraft in various ways that seek to guide the audience's re-evaluation or refiguration of them. It parodies Shakespeare's own dramaturgical practices at the same time, but presents the credentials of its author's stagecraft as being somehow exemplary.
The artisans' "tedious brief scene (5.1.56) offers an inversion of the matter and manner of the framing play, and focuses the tragic potentiality of the conflict between Egeus and the lovers Lysander and Hermia. However, the main emphasis is on the "intents/Extremely stretched, and conned with cruel pain" (5.1.79-80) that the would-be professional players put into their production of "The Most Lamentable Comedy". Although they never intend including scenes of comic by-play in their staging of the tragic love story, they get all the codes and conventions wrong and metamorphose the whole endeavour into a farcical tragedy.
The play-within-the play scene is juxtaposed to the emblematic dream of Bottom, deliberately contrasting two differing modes of perception. Bottom awakes from his dream with the awareness of the futility of his trying to define the indefinable, or trying to report in ordinary language a moment that transcends ordinary experience. What he had perceived, he realises, could only be expressed in poetic terms in the imitative synthesis that emanates from the poet's imagination - those shaping fantasies that the poet's seething brain projects. Shakespeare's comic anatomy of sixteenth century stagecraft reveals how a poet dramatist of Peter Quince's calibre would inevitably fail in the enterprise of writing a ballad about Bottom's dream experience. Only the poet who speaks "metaphorically" to use Sidney's expression, "lifted up with the vigour of his own invention, doth grow in effect another nature, in making things either better than nature bringeth forth, or quite anew, forms such as never were in nature" (p. 23).
The seemingly artless "palpable gross" play is paradoxically itself art that conceals art: in the manner of the fool who hides meaning in metaphor and uses covert allusions, Shakespeare's anatomised clowns offer the spectator/reader what can be considered a close approximation to a "defence" of dramatic poetry in general.

Bibliography

Barish, Jonas, The Anti-theatrical Prejudice. Berkeley: University of California Press, 1981.
Elam, Keir, The Semiotics of Theatre and Drama. London & New York: Routledge, 1994.
Sidney, Philip, A Defence of Poetry, ed. J. A. Van Dorsten. Oxford: OUP, 1997.
Taylor, Anthony B., "Golding's Ovid, Shakespeare's 'Small Latine', and the Real Object of Mockery in 'Pyramus and Thisbe'", Shakespeare Survey, 42 (1990).