In the end scene where the boys are having Christmas, Sam hands Dean a glass of Eggnog and asks him if it needs more kick. The glass was supposed to be nonalcoholic but Jared Padalecki actually dumped most of a bottle of rum into the glass without telling Jensen Ackles. Dean's look of surprise and cough when he drank were both genuine reactions.
During the filming of this episode, Jared Padalecki, who had been having some personal issues, had a panic attack. The doctor suggested that he may have been clinically depressed. While Jared seems to have overcome this or at least manage it well, it was still a factor for him when he ran his "Always Keep Fighting" campaign in early 2015, selling shirts with Sam Winchester's portrait and the slogan to benefit the charity 'To Write Love On Her Arms'. This is a charity that raises awareness and provides aid to people suffering from depression and related illnesses.
Dean asks Sam, "So was I right? Is it the serial-killing chimney sweep?" To which Sam replies, "Yup, it's actually Dick Van Dyke". Dick Van Dyke is famous for playing Bert, the singing/dancing chimney sweep from the Disney classic Mary Poppins (1964).
Dean says the creepy, limping, craptastic Santaland Santa smells like candy and Sam says no, that's ripple. In 1960 E&J Gallo introduced Ripple, a very sweet, slightly fizzy fortified (spiked with extra alcohol) wine. This very low price overly sweet wine was marketed for casual novice drinkers but quickly became the reputed favorite of derelict alcoholics. While Ripple was taken off the market in 1984, that name has become slang for cheap, sweet wino wine.
Sam says meadowsweet is pretty rare and probably the most powerful plant in pagan lore. While meadowsweet is actually common throughout Europe, Asia, and North America it has indeed been very popular since the Bronze Age (3000BC to 1000BC). Its pleasant fragrance and taste made it useful for everything from floor covering to mead flavoring.