Zodiac

The Bill Cipher Wheel is a symbol associated with Bill Cipher, it is believed that it represents characters and objects from Gravity Falls.

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: seen on a table in the hidden bedroom ("Carpet Diem"). The author is seen wearing a pair of glasses like these ("Not What He Seems"). Old Man McGucket, however, believes that it represents himself, though this is then suggested to be incorrect.
 * A question mark: Soos Ramirez - Soos's tee-shirt
 * An open bag of ice: the ice that Dipper retrieves for his friends ("The Inconveniencing"); the ice that Dipper goes to get for Wendy's black eye ("The Time Traveler's Pig"). McGucket suggests that it may represent Will E. Badger, because he is cool, Wax Larry King, who melted, or Blendin Blandin.
 * A crescent shaped symbol: seen on 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 Tent of Telepathy symbol seen on the top of the tent and the back of Gideon's cape
 * A hand with six fingers: the hand on all of the author's journals
 * A llama/alpaca: The second episode in the mini-series "The Mystery in Gravity Falls" suggests that the llama/alpaca (the short refers to it as a llama) could potentially represent Mabel Pines, as there is a llama on one of her sweaters. (NOTE: This series originated in Scandinavia and is not official. Not only was this posed as a suggestion to be left open to interpretation, but the short itself shouldn't be taken as law)
 * A shooting star: Mabel Pines - one of Mabel's sweaters
 * A heart with a stitch in the middle: seen on Robbie's sweatshirt

Mini-series

 * "Old Man" McGucket's Conspiracy Corner Marathon": "The Ice Man"
 * "The Mystery in Gravity Falls"

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 a connection between himself 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 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."
 * Soos, Dipper and Robbie's symbols have all been seen elsewhere. As they are all on articles of clothing, there are other articles of clothing with the same symbols on them.