“Gross shirt”

LUKE: Hey, part of the deal of you staying here is that you work here, and when you work here you will wear proper work attire, and that is not proper work attire. Now go upstairs and change into something that won’t scare the hell out of my customers.
JESS: Whatever you say, Uncle Luke. [goes upstairs]
LORELAI: Gross shirt … good band.

Luke has made good on his promise of Jess having to work in the diner when not at school. Jess is obliging, but still teases Luke by wearing one of his heavy metal tee-shirts to work. This is the Metallica tee-shirt that Jess joked wouldn’t get along with his Tool tee-shirt.

Lorelai immediately makes a note of the fact that she and Jess share a favourite band, both being fans of heavy metal.