RORY: When is dinner ready?
LORELAI: Do I look like a timer?
RORY: I thought you might have set one.
LORELAI: Silly rabbit.
RORY: Timers are for kids.
Lorelai and Rory are referring to the advertising campaign for Trix – a corn-based, very sugary, artificially coloured and flavoured breakfast cereal manufactured by General Mills, and first brought out in 1954. The highly popular marketing campaign began in 1955, and shows a cartoon rabbit who tries to trick children into giving him their cereal. The tagline is, “Silly rabbit – Trix are for kids!”.
Whether the breakfast cereal had anything to do with Richard Gilmore’s pet name for his mother is unknown, but he would have been ten or eleven when the cereal came out, and part of the company’s target demographic.