Or, if you like, intertextuality. Lots of movies today are chock full of references to related movies or other source material. If you're a fan how does it make you feel when, say, in The Force Awakens a bunch of old Star Wars characters return? If you're not a fan do you feel intrigued or maybe left out? Are these shared stories a good thing, letting us have more nuanced characters and plots, or are they a cheap grab for our heartstrings and wallets?