LORELAI: I have a spider whose previous credits include the bathtub scene from Annie Hall trapped under that cup.
DEAN: The size of a Buick?
Buick is a division of the US car manufacturer, General Motors. In the North American market, Buick is a premium automobile brand, selling luxury vehicles positioned above GM’s mainstream brands, while priced below the flagship luxury Cadillac division.
Dean is quoting from Annie Hall, when Alvy describes the spider as “the size of a Buick”. He obviously knows the film, and probably watched it with Lorelai and Rory.
[Picture shows a 1977 Buick – the same year Annie Hall was released].
The Annotated Gilmore Girls 