In the beginning of the movie, there are several photographs on the wall of Jane and Roxy Ryan as young kids with their mother who passed away. These are actual photos of Mary Kate and Ashley Olsen, but with their own mother Jarnette Olsen cut out and replaced.
Bob Saget: As the Olsen twins (wearing bathrobes), go running past him in the streets of New York, he turns around and stares at them, as if he knows who they are but cannot remember their names. Bob Saget played Danny Tanner on the sitcom Full House (1987), in which he was the father of Michelle Tanner (played by the Olsen twins).
The trivia item below may give away important plot points.
The sisters pass by a street vendor in Chinatown selling bootleg DVDs of "Holiday In The Sun 2" (a bogus movie). This is a reference to the Olsen twins made-for-video release Holiday in the Sun (2001). This bootleg DVD is also seen later on among the bootleg merchandise that Jane finds in Ma Bang's Nail Parlor. Other bootleg merchandise she finds include a "Final Recourse" DVD (another bogus movie) and a Simple Plan "Vacation" CD (a bogus CD single for the song the band performed in the film, which also appears on the soundtrack album).