Pop Merrill's Enlisted Records Brief (ERB) denotes assignments to the Army's 1SFOD-D, which stands for 1st Special Forces Operational Detachment - Delta (Delta Force). This is the Army's elite counter-terrorism unit.
During Pop's speech, while talking about his shop, the Emporium Galorium, he mentions a sign that says "Caveat Emptor", meaning "buyer beware". The same sign was inside of Leland Gaunt's shop in Needful Things.
Alan Pangborn's name can be seen on a letter when Nadia is looking through Pop's files. In addition to being a character in season 1, Pangborn was also a major character in both Stephen King's The Dark Half and Needful Things.