Possibly two or three different questions here. I often see the names of famous people and other properties name-dropped (such as in the old "Sailor Moon" novels, which name-dropped Backstreet Boys, X-Files, and Buffy). In my fanfics, I often do similar name-dropping as a way of establishing things about a character. In Stephen King's works, he often includes song lyrics before the story (or before parts of a story) to establish a theme. Similarly, I sometimes quote song lyrics before sections of a fanfic. What are the legalities, though, of doing so in an original published work that's sold for profit? Would I have to contact the owners to get permission to name-drop a movie/series or quote a line or two of song lyrics? Would I have to contact a celebrity to get permission to mention that my character is a fan?