Opens with the quote, "O Christmas Tree, O Christmas Tree, How steadfast are your branches..." from the Christmas carol "O Christmas Tree"
In Central European folklore and tradition (specifically countries that formerly belonged to the Habsburg Empire), Krampus usually accompanies St. Nicholas on his rounds. He punishes the naughty children whilst the Saint rewardes the good ones. He reflects that balance of good and evil, reward and punishment which was a central theme of such folk and fairy tales.
The title is a play on the song "The Twelve Days of Christmas."
The location of the crime scene where Krampus attacked Derrick Bryce and hauled away Quinn Baxter in his sack was under the east end of the Hawthorne Bridge, which has periodically appeared throughout Grimm in scenic camera shots or time lapse photography of Portland.
December 13, 2013 marked the first time where two new episodes aired on the same day ("Cold Blooded" & this one).