X THEORY3 Postmodernism Deconstructionism Intertextuality and Simulacra

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POSTMODERNISM

Argues that all the 'isms', eg. capitalism, communism, are now meaningless - the meta-narratives no longer have the power to explain the world or reality.  It is of course self-contradictory: postmodernism is an ism!
Strinati argues there is a collapse in the high/popular culture divide - all are now equally valid.
Such notions lead to playfulness.
The concept of postmodernism denies definition to some extent, but Dominic Strinati outlined 5 key characteristics in 1995 that are often cited:

1. Breakdown of the distinction between culture and society
2. An emphasis on style over substance
3. Breakdown of the distinction between high art and popular culture
4. Confusions over time and space
5. Decline of metanarratives ['grand theories such as Marxism, Christianity and ... modernism have lost their currency for modern societies']*

DECONSTUCTIONISM

The ironic use of existing conventions in a knowing way; the audience is assumed to be in on the irony.  EG: in Scream the Matthew Lillard character cries out dramatically "I'll be right back", an old horror trope being that this denotes a character will be killed.  The other teens at the party respond with that in mind, in a scene where they're sat watching Halloween.  Craven is poking fun at, or critiquing, the very genre he helped to create with 1972's The Last House on the Left.
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This occurs across all media - this Depeche Mode video is a classic example, deconstructing the band's poor, tawdry image and the male gaze.
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via GIPHY
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INTERTEXTUALITY

A simple but profound concept originating with Kristeva - the preferred reading (Stuart Hall) of two texts are linked; the viewer needs knowledge of the earlier text to be able to follow the preferred reading of the newer text.  TV shows like The Simpsons are built on this, and there is a strong vein of this running through the slasher genre.
To help generate cheap publicity for his 1978 proto-slasher Halloween, director John Capenter cast the daughter of the Psycho's scream queen.
In Scream, the characters are watching Halloween.

SIMULACRA

Scary Movie exemplifies the ideas above - it takes intertextuality to a new level: Scream had the working title of Scary Movie, and this film is a satirical remake, quite literally signposting the conventions (eg the Carmen Electra scream queen sees a sign giving the options for either death or safety... and runs up the stairs where the death sign points to, as the dumb scream queens tend to).
These movies have been much analysed, not least for gender representations.  Baudrillard might argue that this leads nowhere as there is no ultimate meaning behind an endless sea of signifiers; Scary Movie is an expression of many existing ideas or signifiers, which cannot be tracked back to any concrete 'true reality' or meaning.
Ideas like encourage playfulness, as seen in these two films.