Annie taking the hammer out while talking about torture is an obvious nod to her famous leg breaking of Paul Sheldon in Misery.
"Caveat emptor" is Latin for "buyer beware."
Frances Conroy very briefly reprises her role as Martha Lacy from season 1. The actress also appeared in another Stephen King story adapted into a TV series, The Mist (2017)
The camera on Pop's shelf is a Polaroid Sun 660, the model from Stephen King's novella, "The Sun Dog."
Pop opens up an envelope addressed to Alan Pangborn. In addition to being a character in season 1, Sheriff Alan Pangborn was also a major character in The Dark Half and Needful Things.