Zodiac

The Bill Cipher Wheel is a symbol associated with Bill Cipher.

Background
The wheel is quickly flashed at the end of the theme song. When it is shown there is a fast whisper that reveals the code needed to translate the cryptogram seen at the end of the episode.

The wheel is also written in Journal 2 when Gideon is searching how to summon Bill Cipher. The page in the journal featuring the wheel looks different than the page featured in the theme song. Some content on the page is the same, and other is different. The page in the journal contains information regarding Bill Cipher, as well as the wheel. The author states that he had been dreaming of Bill and the symbol for weeks, and he questions the significance of the symbol.

As the wheel appears to represent Bill, he seems to have the ability to summon it around him.

Appearance
The image flashed at the end of the theme song appears to be drawn on a page from one of the journals. The paper has various symbols, writing, and other content written on it including a phrase which can be deciphered with Caesar cipher and reads "STAN IS NOT WHAT HE SEEMS."

When Bill summons the wheel it is a bright, glowing blue. A blue light then flickers around the wheel, briefly highlighting each symbol.

Around the circle are ten small images that have been seen throughout the series. These images, their placements, and the people they represent include:
 * A pair of glasses: the author - on a table in the hidden bedroom ("Carpet Diem"). The author is seen wearing a pair of glasses like this, though they are cracked ("Not What He Seems")
 * A question mark: Soos Ramirez - Soos's tee-shirt
 * An open bag of ice: ??? - the ice that Dipper retrieves for his friends ("The Inconveniencing")
 * A crescent shaped symbol: Stan Pines - Stan's fez
 * A pine tree: Dipper Pines - Dipper's hat
 * A crossed, five-pointed star with an eyeball in the center: Gideon Gleeful - the figure on the top of the Tent of Telepathy
 * A hand with six fingers: the author or Bill - the tracing of the author's hand seen on Journals 1, 2 and 3; when Bill summons the Cipher wheel, the six-fingered hand is the first thing to appear
 * A llama/alpaca: Mabel Pines, Pacifica Northwest or neither - one of Mabel's sweaters; a painting of llamas in the hidden room in the Northwest Manor ("Northwest Mansion Mystery")
 * A shooting star: Mabel - one of Mabel's sweaters
 * A heart with a stitch in the middle: Robbie Valentino - Robbie's sweatshirt

Trivia

 * In Journal 2, on the page with the cipher, the journal has three exclamation points and an arrow pointing to the glasses symbols, suggesting that the author was beginning to see the connection between people and the symbols.
 * The crescent symbol representing Stan's hat was originally different but it changed when the symbol on Stan's fez changed. However, in the theme song the wheel remains the same.
 * The llama/alpaca on the wheel is facing in the opposite direction as the one on Mabel's sweater and the ones on the painting in the Northwest Manor.
 * The wheel is also called "Bill's wheel" and "Cipher wheel" for short.
 * The fan website The Mystery of Gravity Falls coined another name for the wheel, dubbing it the "Wheel of Intrigue."