What is intertextuality?
Intertextuality is the shaping of texts' meanings by other texts. It can include an author’s borrowing and transformation of a prior text or to a reader’s referencing of one text in reading another.
An example of intertextuality:
Psycho Shower Scene
In this scene we see a woman having a shower, peacefully. The camera is positioned above her chest, focusing on her face.
Then we see a shadow approaching the shower curtain, when the shower curtain is pulled open, we hear screeching music, getting louder. This shocks the audience.
After we see a close up of the woman's mouth who is screaming. It then goes back to the person who has a knife in his hand, who starts stabbing the woman. The camera switches between each character. While the music is still the same screeching music.
This scene by Alfred Hitchcock has become famous and many other director's borrow this scene for their own films.
The Stepfather borrows the same sort of scene from "Psycho", when they are in the bathroom and the man is trying to stab the woman with the same sort of knife used in "Psycho". But in this film instead of the woman getting stabbed, it is the man who gets stabbed.