Zodiac

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

History
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: Old Man McGucket believes that the glasses represent 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 needs to stay cool or else he'll melt, or Blendin Blandin (no reason is given but it's likely because Dipper ran into Blendin when getting a bag of ice to help Wendy).
 * 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 Tent of Telepathy symbol seen on the top of the tent and the back of Gideon's cape
 * A hand with six fingers: Ford Pines - the hand on all of the journals.
 * A llama: The 2nd episode of the mini-series "The Mystery in Gravity Falls" suggests that the llama could represent Mabel Pines, as there is a llama on one of her sweaters. (NOTE: This series originated in Scandinavia and isn't official. As such, the short itself shouldn't be taken as law). However, some of the symbolism in "Northwest Mansion Mystery" suggests that the llama could instead refer to Pacifica Northwest, as the symbolism is both in her appearance and in relation to her family.
 * A shooting star: Mabel Pines - one of Mabel's sweaters
 * A heart with a stitch in the middle: seen on Robbie's sweatshirt

When seen in "The Stanchurian Candidate," there are several differences. The six fingered hand is on a journal and the order of the symbols on the wheel are all mixed up.

In The Last Mabelcorn, Bill exits Ford's mind in the display of what some call the Advanced Cipher wheel, representing the different generations in which he had unsuccessful opportunities to bring about Weirdamageddon.

Trivia

 * In Journal 2, on the page with the cipher, the journal has three exclamation points and an arrow pointing to the glasses 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 and Dipper's symbols, as well as the broken heart symbol, 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.
 * Several of the symbols on the wheel can be seen on the infinity sided die.