The movie is dedicated to Lorraine Warren (portrayed in the movie by Vera Farmiga) who passed away two months before the film's release.
(at around 50 mins) The real Annabelle is at the Warrens' Occult Museum in Monroe, Connecticut, kept in a glass case with warning signs. Unlike the doll in the film, it is a Raggedy Ann doll. In one scene, Judy is watching a game show when a couple win a trip to Vegas and a Raggedy Ann doll. This is a nod to the real Annabelle.
The character of Anthony Rios was created as a proxy for Judy's real life husband, Tony Spera. While she and Spera didn't actually meet until adulthood, Gary Dauberman asked their permission to create the childhood bully character to potentially serve as a romantic interest for Judy if the series continues to follow her character as she grows up.
The samurai armor that features in the Warren occult museum is based on Japanese mythology's demonic warrior, the Oni, marking along with the Ferryman the second cultural mythology entity appearing.
Like in Conjuring 2 : Le Cas Enfield (2016), Patrick Wilson does his own singing, as he is an accomplished singer and musical star.