The show uses backwards messages, riddles, and a variety of codes and cryptograms for viewers to crack in order to uncover secret messages. These messages can be found in plain sight at the end of the credits in every episode and hidden throughout the actual episodes. Sometimes the messages can be decoded into something comical, but other times it will be something more serious that will reveal hints and important clues for future episodes or even extra lore on the story and characters. According to Alex Hirsch, the codes for every episode are written out by him and inserted into the episode at the last minute.
Unlike most Western animated TV series where characters have either 4 or 5 fingers, Gravity Falls manages to mix characters having either number. According to former series writer/creative director Micheal Rianda, this is because some characters look better having 4 or 5 fingers on them.
The Mystery Shack is based on the Oregon Vortex, a tourist trap that Alex Hirsch visited while visiting Oregon during his college years.
The character of Mabel is based on Alex Hirsch's twin sister, Ariel. Alex Hirsch used his own grandfather for the inspiration for Grunkle Stan. Soos is based on an old college buddy of Alex Hirsch's named Jesús Chambrot.
At the end of the opening intro, a picture is displayed of a wheel with Bill Cipher in the middle and symbols around him. Each symbol represents a character in the show, though the meanings behind the symbols are not revealed until the series finale. The picture also shows the Konami code and a cryptogram that says "Stan is not What He Seems." This is a reference to "The Owls are not What They Seem" from Twin Peaks and is a foreshadowing to the episode "Not What He Seems."
Bill Cipher, the dream demon, can see through his depictions (a triangle with an eye). His depictions are everywhere in the show, which means he has an appearance in every episode of the show. The crew behind the show put his depictions everywhere so the audience knows that he is watching the Pines family ALL the time.
Alex Hirsch based the entire series on the exciting summer he wished he and his twin sister, Ariel could have had as children. Since most of their actual summers were pretty boring, Hirsch would spend time daydreaming about encountering gnomes or solving mysteries.
On November 20, 2015, Alex Hirsch announced via his Tumblr that Gravity Falls would be ending with it's second season in the form of the hour-long series finale. In the Tumblr post, Hirsch stated that the show wasn't being canceled, it was being finished and that this was 100% his choice not Disney's. Hirsch said he had planned out a story for Gravity Falls from the beginning and that it was simply reaching it's natural conclusion. Hirsch never wanted Gravity Falls to continue on with multiple seasons, just because it was popular, until it jumped the shark or faded into obscurity like numerous other children's cartoon shows. Additionally, Hirsch also said that by ending the show after it's second season, it just means that this chapter of the story is done and for now, he's done telling the story. However, Hirsch has been keen to remind fans that he has left the door open for future Gravity Falls stories and that he would be willing to return to the Gravity Falls world someday in the future.
The symbol in Stan's fez (a form of crescent shape) was changed in the middle of season 1, due to an issue with a country where the symbol was considered offensive. In Gravity Falls: Boss Mabel (2012), the goat Gompers ate Stan's fez during the credit scene. In the next episode, Gravity Falls: Bottomless Pit! (2012), Stan appears with a different symbol on his hat (a shape resembling Pac-Man). This same symbol was also used in the opening sequence. Oddly enough, the symbol was not changed in the picture with Bill Cipher's wheel displayed during the final split-second frame of the intro.
Wendy and Robbie met at a 5th grade birthday party. He pulled her pigtails and she punched him in the face, chipping his tooth. He remembers but she doesn't.
At the end of the intro song, there is a whisper that sounds like "I'm still here." Reversing the audio reveals that it says "three letters back." later it says "switch a with z" after that it says "26 letters" in season 2 it says "key vigenère" all of these are hints to the cryptogram at the end of the episode in the episode "not what he seems" the whisper is changed to "not what he seems"
According to Alex Hirsch, Dipper and Mabel's first names are their parents' middle names.
There is a lot of continuity in Gravity Falls. Often times something will be changed and stay changed. This includes but is not limited to the "S" in the Mystery Shack sign getting knocked off in the sign in "Head Hunters", Stan wrapping his hand in a bandage at the end of "Society of the Blind eye", and many other things, some of which have a special significance to the show's lore, which is discussed in the behind the scenes special, "Between the Pines".
Creator Alex Hirsch appears in the background of several episodes. He is the man in a red flannel jacket and red-ish brown hair.
If you search for the Gravity Falls location on Google Maps it'll take you to The Oregon Vortex.
Film director David Lynch was asked to voice Bill, but declined. Alex voices the character with what he calls a "bad impression" of Lynch.
Dipper and Mabel Pines are from Piedmont, California, the place where show creator, Alex Hirsch, is from.
The Time Baby is "the last son of an extinct race of time giants" (according to Bill Cipher).
Stan did "The Stan Wrong Song", featured in the end credits of Gravity Falls: Boss Mabel (2012), 48 times before he got it right.
A supernatural creature highlighted in the show's mini-series, "Dipper's Guide to The Unexplained," called the Hide-Behind, was described first in a manner similar to the popular urban legend, Slenderman. On a similar note, a popular Gravity Falls meme was Slenderman making numerous vague appearances throughout episodes, which showed him photo shopped into episode screen caps, despite never making an official appearance.
The soda Pitt Cola is not only a joke (because of the peach pit inside it) but is a reference to Joe Pitt, one of the directors of the show.
Gideon is at least 10 years old and can be seen as a baby when Dipper and Mabel travel back in time in Blendin's Game.
Grunkle Stan has been practicing the same coin trick since 1982 and still can't master it.
During an interview with creator Alex Hirsch, he revealed that he is a huge fan of the X-Files and has been since he was a kid, and that Gravity Falls was influenced greatly by it during its creation.
All throughout Season 2, at various points in episodes, random words can be found etched into the background. These words are actually keys for solving Vigenère ciphers provided on a puzzle piece after the credits. These puzzle pieces fit together to create a Cryptic Page, with Grunkle Stan and Grunkle Ford's faces in the center of it. Along with these ciphers, combinations of Atbash, Caesar and numbered ciphers are seen after the credits in sections of a "Cryptic Page".
Alex Hirsch created a real life treasure hunt called "Cipher Hunt". The goal of the hunt was to find an actual statue of Bill Cipher, briefly glimpsed in the credits of the series finale, by retrieving clues and decoding codes, riddles and backwards messages hidden in various locations all around the world! Some clues were found in places as far away as Russia and Japan, but most were located within the USA. One clue involved a 2,000 piece puzzle, which took fans nearly a week and a half to complete with almost always someone working on it. While working on the puzzle, some fans took sleep shifts and others didn't sleep at all. After two long weeks, the statue was found in a forest in a small town called Reedsport, Oregon. The first ones to the statue received a prize, although the hunt was mainly about the journey and not the destination. The hunt began on July 20, 2016 and finished on August 2, 2016. Both the Bill Cipher statue and the Cipher Hunt puzzle are now on display at Confusion Hill, a tourist trap very similar to the mystery shack. There is also a treasure chest in the gift shop for fans to take and leave treasures for future Cipher Hunters, as well as a log book for fans to write down what state or country they traveled from, the time and date they "found Bill" and also list the item(s) they left in the treasure chest.
Northwest Mansion Mystery was the first episode that Stan didn't appear. He was not even mentioned. It was the second time Soos didn't appear but it was the first time he was not even mentioned.
Bigfoot can be seen in the opening for a split second. This is brought up by Bill Cipher in Gravity Falls: Dreamscaperers (2012) when he displays a sequence of images showing that he knows lots of things though it probably is just an Easter egg.
Even though voicing Gruncle Stan and Soos, the oldest of the main characters, Alex Hirsch is actually the youngest of the the main cast. He is younger than Jason Ritter by 5 years, Kristen Schaal by 7 years, and Linda Cardellini by 10 years.
Dipper's favorite band is a nerd rock band called "The Bad First Impressions." But he secretly listens to Top 40 hits as well.
In the real-life edition of Journal 3 it is revealed that Gruncle Stan stole a dinosaur egg from the caverns in the episode "The Land Before Swine" and it hatched into baby Compsognathus which they named Compy. Compy picked the pockets of tourists and scared away customers, taking their money. As a result, they had to give Compy away to Farmer Sprott.
The Gravity Falls Pilot that was used to sell the show to Disney initially went unaired and unreleased to the public for several years. A few screenshots of it were available online, but no voices, music, animation etc. It wasn't until the "Cipher Hunt" in 2016 that Alex Hirsch made the promise to finally release the unaired Pilot to the public, but only if fans completed the 2000 piece puzzle that was a clue in the hunt. It took a week, but fans succeeded in completing the puzzle. Upon its completion, Alex Hirsch made a surprise appearance and signed the puzzle and then signed autographs and took photos with the fans who were there. Hirsch kept his promise and uploaded the Gravity Falls Pilot to the Internet in weeks following the hunt. The Pilot can now also be found on the Gravity Falls complete series collectors edition DVD/Blu-Ray which was released in 2018.
In the Gravity Falls Pilot, the book that Dipper has is called "Dr. Crackpot's Book of the Damned" rather than "Journal 3".
Blendin's name (Blendin Blandin) is a pun, because he is hidden in the background. He is "Blendin'" with the crowd.
The evil demon, Bill Cipher, is based on the Eye of Providence symbol, but wearing a top hat and a bow tie.
The names of multiple characters make references to things in real life. Dipper is named after the Big Dipper constellation (due to him having the Big Dipper in the form of a birthmark on his forehead), Bill Cipher is named after the dollar BILL and the CIPHER wheel, and Pacifica Northwest is named after The Pacific Northwest.
"Gravity Falls" has two ties to Scooby-Doo. The character of Wendy is voiced by Linda Cardellini, who played Velma in the two live-action theatrical Scooby-Doo movies, and Grey Griffin (formerly Grey DeLisle), who voices Daphne in many of the Scooby-Doo animated movies, provides additional voices on a regular basis for "Gravity Falls".
Alex Hirsch provides the voice talent for more than five characters in Gravity Falls, including Grunkle Stan, Soos, Old Man McGucket, Bill Cipher and the gnomes.
Several episodes make reference to the phrase, "Trust no one." This is a direct quote from "The X-Files", which heavily influenced the show.
Dipper is the only character to appear in every episode of the series. Mabel is in every episode except "Weirdmageddon: Part 1," Grunkle Stan is in every episode except for "Northwest Mansion Mystery," and Soos is in every episode except for "Irrational Treasure," and "Northwest Mansion Mystery."
In 2013, Alex Hirsch and the Gravity Falls crew took a 4-day road trip called, "Mystery Tour 2013", to find "the weirdest tourist traps" all across Oregon and Northern California. Hirsch and company left behind several drawings of Bill Cipher in various spots, such as telephone poles, signs and trash cans, and released photos of them over Twitter for fans to find. The fans who took a picture of themselves in the same spots received varying "Mystery Prizes".
Episode titles are often movie references, examples include: The Time Traveler's Pig, Fight Fighters, Little Gift Shop of Horrors, Soos and the Real Girl, and Tourist Trapped.
In the episode's "The Time Traveler's Pig" & "Blendin's Game" The two agents who take Blendin in and chasing after him are named "Lolph" and "Dundgren" an obvious reference to the Action Star: Dolph Lundgren.
The only sweater Mabel wears more than once is her shooting star sweater. She wears it in S1 E1 "Tourist Trapped", S1 E4 "The Hand That Rocked Mabel", and in parts 2&3 of the "Weirdmageddon" series. She also wears it in the title sequence. Mabel also technially wears the same sweater in the episodes "Not What He Seems" and "A Tale of Two Stans," but the events that happen in both episodes are back-to-back, so she wouldn't have been able to change her sweater.
In the next three years following Gravity Falls' conclusion we got at least two new things related to Gravity Falls each summer. In summer 2016 we got "Journal 3", "Dipper and Mabel and the curse of the time pirates treasure", the "cipher hunt" and the official Gravity Falls art show. In summer 2017 we got the "Journal 3 special edition" and the official Gravity Falls coloring book, "don't color this book! It's cursed!" And in summer 2018 we got the Gravity Falls complete series DVD/Blu-Ray and "Gravity Falls Lost Legends".
Acclaimed filmmakers and authors Guillermo Del Toro and R. L. Stine are fans of the series.
To coincide with the release of journal 3, Gallery Nucleus in Alhambra, California held a Gravity Falls art show called, "Farewell to the Falls: A Gravity Falls Art Show" on August 6-21, 2016. 50+ artists, many of whom worked on the series, exhibited their work and series creator Alex Hirsch was there signing autographs. Some fans camped out overnight to see the show and some works of art sold for more than $500.
According to Dipper, Gravity Falls is not on most maps. On Stan's campaign Twitter page, Stan explains that the reason for this is because he "got in a fistfight with the state mapmaker" causing Gravity Falls to be removed from maps years ago - part of Stan's campaign was to put Gravity Falls back on the map.