I've recently noticed that in a lot of pop culture reference heavy shows or movies, like Community, Suits, Deadpool... they always mention the movie they took it from. As in, another character is confused about the line and they need it explained, or something like that.
Is that required? To name the place you took the quote from or can a character just say a line if he does it in a way that contextually implies he's quoting something, or if the quote is famous enough that the majority of readers recognize it?
For example - is it safe and sound to quote something like the "One Ring to rule them all" short poem from Lord of the rings? Or would that be complicated because it's also from a novel that has different copy rules to movies?