Intertextuality is the word used when directors/film makers become inspired by other movies, incorporating them within their own pieces.
A few examples of Intertextuality is within The stepfather we find the spiral staircase in the high angled shot a lot, this idea was originally taken from the thriller what lies beneath.
another example of intertextuality is the shower scene within the stepfather here we see the murder in the plain white bathroom with the victim as in the same way we see the murder in the plain white bathroom with the victim in the film physco. its identical in the way that the non digetic sound of water running is used allow we see a close up of the shower railings being ripped off. the Intertextuality was successful in this case.
Knife blocks is another one for intertextuality, we see knife blocks in The Stepfather and the same knife blocks in fatal attraction whenever we see knife blocks we instantly know danger is about.