In S1E18, Lorelai is talking to Sookie about Gran offering Rory a trust fund. Lorelai sees that it’s getting late and says, “I have to change and go to tea with Gran and the cast of ‘Gaslight.'”
“Gaslight” is a 1944 movie (based on a 1938 play) starring Charles Boyer and Ingrid Bergman. The story is about a murderer who marries a woman and then convinces her that she is going insane just to access the woman’s aunt’s fortune. He manufactures strange situations and then tells the woman that she must be imagining things. In the end, the woman finds out what’s happening and tortures her husband briefly before having him arrested.