In S1E7, Luke rants to Lorelai about how he doesn’t want to decorate for the Autumn Festival, and he tells Lorelai that she looks concerned, which she denies. Later, after Rory leaves Lorelai sitting alone in the diner, Luke says to Lorelai, “Not going to say you look concerned.” Lorelai responds, “Not going to talk about how good you’d look dressed like one of the guys from ‘The Crucible.'”
“The Crucible” is a 1953 play that has been adapted into film several times. It centers around Puritans in the Massachusetts Bay Colony during the Salem Witch Trials. Lorelai mentions “The Crucible” because she knows Luke would never decorate for the Autumn Festival, much less dress up like a Puritan or a Pilgrim to celebrate Thanksgiving.