A bookends-style joke for the episode. At the beginning, Jess was in trouble for wearing his “inappropriate” Metallica tee-shirt to work at the diner. Now he comes out dressed as a Luke clone, in his own checked flannel shirt and backwards baseball cap, claiming he assumed that it was the uniform for the job.
While Luke berates him, Rory and Lorelai look on in amusement. Jess can feel gratified that once again he has managed to get Rory’s attention through his clothing choices.
It is also another “mirroring” scene, where Luke and Jess are presented as mirror images of each other, just as when Jess first stepped off the bus into Stars Hollow.