LORELAI: There has not been one moment over our entire stay when she [Sammy] has not been right there.
LADAWN: On the stairs?
LORELAI: Yes.
LADAWN: Oh, she’s hardly ever on the stairs.
RORY: Forget it Jake, it’s Chinatown.
Rory is referencing the 1974 mystery film Chinatown, directed by Roman Polanski, with screenplay by Robert Towne, and starring Jack Nicholson as private investigator J.J. “Jake” Gittes. Set in 1937, the film was inspired by the Californian Water Wars, disputes over southern Californian water where Los Angeles interests gained water rights in the Owens Valley (in actuality, these occured at the beginning of the 20th century).
At the end of the film, the antagonists force Jake to drive them to Chinatown, where his love interest Evelyn (Faye Dunaway) has sought temporary refuge at the house of her butler. Police are already waiting to arrest Jake, and during the confrontation, they kill Evelyn. The police free Jake, and his associate Lawrence Walsh (Joe Mantell) advises him, “Forget it, Jake. It’s Chinatown”.
Chinatown is regarded as a classic film, and Robert Towne won the Academy Award for Best Original Screenplay. The screenplay has a legendary status among film makers, and is often cited as the greatest example of film writing.
In this scene, we discover that Sammy the cat is actually a female, with her name presumably short for Samantha.
The Annotated Gilmore Girls 