What is the proper use/copyright requirements if I want to allude to a copyrighted character in another work? Can I do it? Specifically, I’m looking at a single reference – as in a single line of dialog, something like “You’re quite the Nancy Drew, aren’t you?” (this is an example, not a quote). Am I required to get permission to use the term “Nancy Drew” from the copyright holder (I am referencing their description of the character, I suppose, but it’s a term that’s commonly used), or is noting the copyright holder enough?
Copyright becomes an issue if you plan to use that character in your work. If, for example, you want Nancy Drew herself to be a character in your work. To talk about a pop culture reference, whether it’s a character, a famous person, a book, a movie, etc., is not a copyright issue. Therefore your example is not a copyright issue at all, and you don’t need to reference the copyright holder or obtain permission.