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 and usually use the atbash, caesar or vignere cipher. 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 encountered while visiting Oregon during his college years.
On November 20, 2015, Alex Hirsch announced via his Tumblr that Gravity Falls would be ending with its 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 its 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 its second season, it just means that this chapter of the story is done and for now, he's done telling the story. 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.
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.