Kristen Kingle/Isabelle is made up to look like Kim Novak in the film Vertigo ('58) A film which deals with a man obsessed with the double of a woman who's death he feels responsible for.
The Latin phrase inscribed on Gordon's father's ring, "Dum Spiramus Tuebimur"(While we breathe, we shall defend) is also the motto of the United States Army National Guard's 133rd Field Artillery Regiment.
Valerie Vale's line to Jim Gordon when he comes to visit her in the hospital at the start of the episode ("Stop the press") is the same line The Joker says when he first sees a photo of Vicky Vale in Batman (1989).
The Penguin's tie changes from a purple one in the scene with Edward's girlfriend to the black and silver one at the dinner.
Isabella mentions "Anthony and Cleopatra, Romeo and Juliet, Othello and Desdemona". These are characters in plays by Shakespeare. Namely "Anthony and Cleopatra", "Romeo and Juliet", and "Othello" respectively.