The Stand By Me segment makes reference to the real-life fates of two cast members. We are told that Cleve, the fat kid, grew up to marry Rebecca Romijn, just as Jerry O'Connell did. We are also told that Quag died of a drug overdose outside the Viper Room, a reference to the real-life death of River Phoenix.
The title is based on the Christian story of the birth of Jesus Christ who was visited by three kings, magi or wise men that came to worship him and brought him gifts of gold, frankincense and myrrh. It also refers to the fact that all three of the films being parodied were based on Stephen King stories.
The trivia item below may give away important plot points.
In the Misery storyline of the episode, Stewie becomes upset with Brian for bringing his children's book character, Snuggly Jeff, back to life with a child's wish, calling it lazy writing. The movie "Ted", created by Seth McFarlane and released 3 years after the episode, starts with the titular character being brought to life by a child's wish. The movie also ends in a similar circumstance.