[The girls start dancing. Kirk watches them as Rory walks over to him.]
RORY: How come you’re not up there Kirk?
KIRK: Oh, I don’t tap anymore. Bum knees.
This is the first indication we have of Kirk’s artistic leanings and dance training, later retconned so that he is actually a past student of Miss Patty (even though he had never met her in their first encounter on the show, in Cinnamon’s Wake).
The Annotated Gilmore Girls 