When Trish dumped her bodyguard at the record store and hides in the cab, the bodyguard comes out and yells, "Trish! I'm gonna find your Aaliyah-lookin' ass!" "Trish" was portrayed by late vocalist, Aaliyah.
While in the record store we see many posters of different artist (such as R. Kelly) after Trish leaves the store Maurice stays and when he realizes that Trish has left, it shows him running towards the door and there is a poster of Aaliyah (the actress/singer that plays the character Trish) by the window.
In one scene, Han breaks into apartment number 2600 by picking the lock. The number 2600 comes from Computer Hacking subculture, and is a symbol for the type of technical insight involved in circumventing security measures (such as picking a lock).
Jet Li, DMX, and Anthony Anderson also star together in the action flick "Cradle to the Grave". Aaliyah was also set to star alongside them until her untimely death. Her role was later given to Gabrielle Union.
The x-ray "bone-breaking" sequences in the film are similar to a famous scene in Sonny Chiba's The Street Fighter[Gekitotsu! Satsujin ken (1974)]. However, the ones in Romeo Must Die are far more advanced, presumably through the use of CGI.
The trivia items below may give away important plot points.
An alternate version of the ending was filmed in which Han and Trish kiss. It was reported that this ending was not liked by the test screening audience who were uncomfortable with an interracial romance. But according to Jet Li, it was deemed inappropriate for Han to be too romantic after seeing Chou's suicide so the ending without the kiss was used instead.