The opening credits changed slightly every week, reflecting Jake's changes to the time line and/or foreshadowing events in the episode.
The story that Jake tells Mimi is taken from the films El padrino (parte II) (1974) and El padrino (parte III) (1990).
In the Stephen King novel which serves as the basis for the TV show, the main character travels back to 1958. In the show the rabbit hole takes him to 1960.
During the opening credits of some, but not all episodes, a diagram of a serpant eating its own tail is shown in yellow with a black background. This symbol is known as the ouroboros. The ouroboros has several meanings interwoven into it. Foremost is the symbolism of the serpent biting, devouring, or eating its own tail. This symbolizes the cyclic Nature of the Universe: creation out of destruction, Life out of Death.
Another one of the many references to other Stephen King books and movies: one of the stores visible on the Main Street in Lisbon, Maine, is Blue Ribbon Laundry--also the name of the business where Margaret White (mother of Carrie) worked in the novel Carrie.