In S1E13, Rory tells Lane that Paris, Madeline, and Louise are coming over the next day for a school project. Lane says, “All three of ’em, huh?” Rory responds, “Double, double, toil and trouble.” Lane adds, “Well, it should make for an interesting afternoon.” Rory says, “With the pricking of my thumbs, something wicked this way comes.” Lane comments, “You’re doing very well in that Shakespeare class, aren’t you?”
Both of Rory’s quotes are lines from Shakespeare’s “Macbeth.” “Double, double, toil and trouble” is part of a song that the three witches sing in their cave as they are working over their cauldrons. “With the pricking of my thumbs, something wicked this way comes” is a prediction from one of the witches that Macbeth is about to arrive at their cave in search of prophesies.
Personally, I always think of the melody these lyrics are set to in “Harry Potter.”