can also happen visually,
for example, in Bas Lurhmann's Moulin Rouge, where the lovers are on top of the elephant with their arms out... it's making an intertextual reference to other love tragedies such as James Cameron's the Titanic.
That was the first example ever given to me about intertextuality and I understood that instant.
Then you use this by saying the intertexual reference suggests parrallels such as that their love is pure, they're meant for each other but it will end tragically... stuff like that.