Dennis mentions it when Nina says she saw a sad movie.
Nina watched this movie, made her sad because of all the clothes that sank.
Elliot is depressed because Christmas is too commercial, brings a sorry little tree, even wears a striped sweater.
Narrator uses similar lines, even sings parody of "You're a Mean One"; Finch ruins Christmas by replacing presents.
Nina's subplot where she doesn't believe in J. Crew.