Did you notice the story’s (allusion, illusion) to romeo and juliet?

An allusion is a reference to something, usually an indirect reference to a statement by another or to a hint or suggestion, a passing or incidental reference.
An illusion is a fanciful vision or a false impression or idea, a mental state in which one attributes reality to something unreal.

For example: The tv show "Castle" has made several allusions (references) to the tv show "Firefly", thrilling fans of both shows.