Time
Time is especially crucial to the plot of the first-half of the movie: Cop 223 is obsessed with expiration dates on food, the woman in the blonde wig kidnaps a man's daughter and threatens to keep her for 24 hours before killing her, Cop 223 and the woman in the blonde wig spend the eve of his 25th birthday together. But more broadly, the film's narrative treats time in an impressionistic, slippery way, making the viewer unsure of how the film's events relate to one another. He blurs the short-term chronology of events with woozy editing techniques and through repetition of specific scenes and pieces of music. Just about the only point when time makes sense comes with the end of the film, when we return to the Midnight Express a year later, when Faye has come to visit her uncle, only to find that Cop 663 has bought the restaurant.
Longing
Longing is a common theme in Wong Kar-wai's films, and his stories are often driven by missed possibilities, unrequited love, and regrets about what could have been. Significantly in Chungking Express, we encounter two heartbroken police officers. They are aimlessly forlorn, torn up over their recent exes, but also quickly hung up on new women. We see those women longing too. The woman in the blonde wig, in her own cold way, obviously longs to be out of the crime business, while Faye both longs for Cop 663 and yearns for an independence that living in Hong Kong and working for her uncle just can't afford.
Doubles
The double is a classic cinema trope used most famously by Alfred Hitchcock in Vertigo. In Chungking Express, Wong Kar-wai employs the theme to build a dream-like logic in the film, giving the viewer a sense of uncanny similarity in a bustling Hong Kong where so many of the faces that pass on the street are ones our characters will never see again.
Sometimes, Wong illustrates parallel lives, such as the two police officers who are the focus of two different stories, or the two women in blonde wigs involved with the same crime boss. Sometimes, Wong simply tries to instill a curious sense of coincidence, such as the fact that the first cop's love interest is named May and the second's is name Faye, or through both of Cop 663's love interests working as airline attendants. We also see visual doubles many times throughout the film, especially in shots where Faye's likeness appears in a mirror, creating an on-screen symmetry.
Food
Much of the film's plot and comedic relief involves food. The Midnight Express fast food spot is the one of the main locations of the film, tying both stories together, and much of what we learn of the two cops' lives is teased out through their orders at the restaurant. Furthermore, in the first story, Cop 223 is obsessed with the expiration date on packages of food, a motif that is poetically tied up in the shot when the woman in the blonde wig kills her superior in the drug operation, revealing his "expiration date." Food is also what Faye uses to get Cop 663's contact information, stopping him in the middle of his lunch in a market to make him help her carry a box of food back to her uncle's restaurant. Food is a thread that ties together the relationships in this film.
Pop Music
Over and over again, we hear the same handful of songs, namely "California Dreamin'" by The Mamas and the Papas, "Things in Life" by Dennis Brown, "Zombie" by The Cranberries, and "What a Diff'rence a Day Has Made" by Dinah Washington. Wong Kar-wai uses these pop songs over and over again to lend the film a cyclic feeling, enhancing its overall dreamy atmosphere. But they also function as an extra-narrative tool, helping us to reflect on the progression of these character's stories every time we hear a song play. This is a savvy maneuver in a film with such a barebones plot, since it might be otherwise difficult to trace the movement of these character's inner lives.
Ennui
Ennui, or boredom, is one of the defining moods of art and culture from the 1990s, and Chungking Express is no exception. Faye lives Gen X ennui in the most typical way: she's unable to care about her job or even commit to pursuing Cop 663 directly, and all that gets a rise out of her is playing "California Dreamin'" at top volume. But we also see ennui in the main characters of the first half of the film, with the aimless Cop 223 and the detached woman in the blonde wig.
In and Outside the Bounds of Law
The two main cop characters in this film are juxtaposed with their supposed outlaw opposites. Cop 223, of course, falls for the woman in the blonde wig, who commits a bevy of crimes including drug smuggling, kidnapping, and murder. It's a funny example of just how poor of a fit our first cop is for his job. Later on, in the second half of the movie, Cop 663 runs into his ex into a convenience store, and watches her run out and hop on the back of a motorcycle. This one is less explicit, but the motorcycle outlaw is a classic type in movies dating back to the '60s, and surely we're supposed to believe that Cop 663's girlfriend left him for someone wilder, dangerous, and maybe even criminal.
