The line spoken by Sir Michael Caine, which is a constant theme in the movie, "There's a crack in everything, that's how the light gets in", is lyrics from the Leonard Cohen song "Anthem".
When you see the pictures in Sir Michael Caine's apartment, you also see a framed Batman logo, Caine played Alfred in The Dark Knight trilogy, and Hans Zimmer also does the movie score for this movie, as well as the aforementioned trilogy.