The "Gravity Falls Main Title Theme," composed by Brad Breeck, is the opening theme song played over the title sequence to Gravity Falls. The official theme song is available on iTunes for $0.99. Beginning with "Northwest Mansion Mystery," a shortened version of the theme is used in episodes that are longer than usual. The "Weirdmageddon" episodes use a corrupted version of the song.
A shortened version of the main title —15 seconds long instead of the regular 41— is used in episodes that are longer than usual. These are:
- "Northwest Mansion Mystery"
- "Not What He Seems"
- "The Stanchurian Candidate"
- "The Last Mabelcorn"
- "Dipper and Mabel vs. the Future"
The Weirdmageddon story arc episodes use corrupted versions of the theme song, along with apocalyptic opening sequences showing the destruction and weird changes Gravity Falls suffers during the event, like an up-going waterfall or Paul Bunyan's statue coming alive, and many Bill images and references.
"Weirdmageddon Part 1" uses an opening sequence replacing every single main character with Bill and his friends. In this apocalyptic version, Dipper is the only character normally in the opening screen that still appears: he's seen as a human skeleton wearing the blue and white pine hat that appears instead of the normal horned monster skeleton, even if only as a resemblance. Bill Cipher's page is seen with a hole where Bill's picture should be, nodding to the fact that he has finally entered Gravity Falls' world.
"Weirdmageddon Part 2" uses a shortened version of the corrupted theme song and opening sequence.
"Weirdmageddon Part 3" also uses the corrupted song and sequence, but it has the regular images for introducing Dipper, Mabel and Stan.
Gravity Paws version
Unused and alternate theme songs
A demo reel of music for the show was released in 2011 by Dan Cantrell with singers chanting the title of the show. Neil Cicierega also made two more theme songs.  There were two other themes considered for Gravity Falls: one instrumental and the other lyrical. These were relegated in favor of Breeck's work. Breeck had also composed an alternate theme song which would eventually be used in the 2014 San Diego Comic Con trailer for the then-upcoming season.
Alternate theme songs used in special episodes
W-H-A-T weather vane spins; Dipper pulls his jacket close to himself as the wind blows fiercely; moon develops a pupil and looks at Dipper (it was actually Bill Cipher's eye) - S02 E04 Sock Opera
Dipper holds a lit portable lantern; Dipper, Wendy, Soos and Mabel descend a flight of stairs; Wendy opens a circular metal door - S02 E02 Into the Bunker
Dipper talks as he holds Journal 3 up, in front of his Big Mysteries bulletin board (with string linking Bill Cipher, Gideon, Town, Shack, Author) - S02 E01 Scary-Oke
Rodent (wearing cap with the word pizza) and bird (wearing a cowboy hat) mechanical robots come to life; both robots' eyes turn red and light up - S02 E05 Soos and the Real Girl
Dipper wielding a spade as he stands guard in front of Mabel and Waddles while shadows of zombies approach the three - S02 E01 Scary Oke
Golf cart leaps over a volcano labelled "Bonus Hole!", volcano erupts sending the golf cart up even higher; golf cart lands on the ground, showing its passengers to be Dipper, Pacifica, and Mabel - S02 E03 The Golf War
Puppets of Grunkle Stan, Dipper, Mabel, Soos, and Wendy - S02 E04 Sock Opera
Rodent mechanical robot wearing cap with the word pizza, slices through a wall with its paw and slams its paw into the ground, missing its targets: Mabel, Melody, and Dipper - S02 E05 Soos and the Real Girl
In a darkened attic, Dipper opens Journal 3 on the ground to read it, with Mabel and Grunkle Stan quickly moving in to also read the Journal; Zombies walking, more zombies emerge from the ground - S02 E01 Scary Oke
Dipper and Mabel walk while Dipper talks, a shadow of Bill Cipher eerily follows the Pines twins - S02 E04 Sock Opera
Front view of Grunkle Stan illuminated by a spotlight; then back view of Grunkle Stan standing in front of the portal, two bolts of electricity fire from the portal - S02 E01 Scary Oke
Mabel, Dipper, Soos, and Wendy in a room with mysterious red symbols, the room begins closing in on them from all sides - S02 E02 Into the Bunker
Lolph, Blendin Blandin (pointing at himself), Dundgren - S02 E08 Blendin's Game
Lazy Susan at a phone booth, being approached from behind by two hooded figures - S02 E07 Society of the Blind Eye
.GIFfany and Soos - S02 E05 Soos and the Real Girl
Dipper and Mabel at a mini golf course at night, standing in front of a windmill with light emanating from inside the windmill - S02 E03 The Golf War
Dipper and Stan, a giant clay hand grabs Stan from behind - S02 E06 Little Gift Shop of Horrors (S02 E06.3 Clay Day)
Pacifica getting dragged from behind into vegetation - S02 E03 The Golf War
Wendy kneeling to wrap her right knee with her green flannel shirt, and then standing up - S02 E02 Into the Bunker
Gideon lying in his prison cell bed, then he opens one eye as something from outside the prison cell window is bright enough to cast a beam of light upon Gideon; Agents Power and Trigger show their badges - S02 E01 Scary Oke
Dipper on the roof at night, holding a laptop in his hands, a spotlight shines on Dipper; back view of Dipper as he faces an eye which forms into Bill Cipher; blue light emanates from Bill Cipher - S02 E04 Sock Opera
"You Made Me Realize" misconceptions
The main theme is often mistaken for the song "You Made Me Realize," due to its strong similarities to the real "You Made Me Realize" song Breeck wrote for MTV's Awkward. "Made Me Realize" is commonly mistaken for the extended version of the Gravity Falls theme song. It is also stated on Breeck's website that the two songs are indeed different, and not related to each other.
- Intro: "Gravity Falls Main Title Theme"
- See also: List of allusions
- There is a quick glimpse of a large, hairy figure that appears to be Bigfoot.
- Towards the end of the song, a whisper plays and sounds like "I'm still here." But if it is played backwards, the whisper is revealed to be "Three letters back." This is how one solves the cryptograms at the end of each episode.
- In "Double Dipper," a new message is whispered: "Switch A with Z." It is an explanation to the "ATBASH" cipher.
- Starting in "Bottomless Pit!," the whisper changes to "26 letters," a reference to the "A1Z26" style substitution cryptogram, which uses numbers to stand for letters of the alphabet.
- In Season 2, starting with "Scary-oke," the whisper is now "Key Vigenère," referring to the fact that the cipher at the end is a Vigenère cipher that requires a keyword hidden in each episode.
- In "Not What He Seems," the whisper is changed to "not what he seems."
- It changes back to "Key Vigenère" the episode after that, "A Tale of Two Stans."
- Towards the end of the theme song when the title shows up, a stamp can be seen near it. The number 618 can be seen on it, which is a reoccurring number in the show.
- In the episode "Little Dipper", right before cutting to the theme song when the Pines are discussing what else to watch on T.V., Mabel states that 'the theme song is [her] favorite part'.
- The cryptogram at the end of the song is "Stan is not what he seems."
- The television version of the song features the whisper and a flashing scene of a journal page of Journal 2 with Bill on it. But the animatic version has no whisper and instead of the journal page, a six-fingered hand with the number 3 and astrological symbols all over it appears.
- As the pictures are thrown down, several of the antagonists in the show can be seen, including a gnome, Gideon Gleeful, Blendin Blandin, the Summerween Trickster, and the Pterodactyl.
- Additional pictures portray mythical creatures from North American folklore, including the Fiji Mermaid, the jackalopes, and the Bat Boy.
- The bottom half of Alex Hirsch's face is seen in one of the many photos between the jackalopes and the Hand Witch's hand.
- On some international airings of the show, and on SAP, the whisper at the end isn't heard.
- Dipper's bag has a sticker that says Piedmont on it, referencing the birth city of Alex Hirsch.
- Dipper seems to be inspecting some runes or symbols before he is startled by the skeleton. The symbols look similar to the ones in the game "Mystery Shack Mystery."
- The symbols are (from top to bottom) the Norse runes for U, M, O, and A.
- The runic symbol for "O" (as mentioned above) is from Elder Futhark. It is "odal" and means real estate, or non-movable property. It is the last symbol in the futhark.
- In two different scenes, Dipper appears to have much thicker eyebrows.
- At the end of the theme, Bill Cipher's entry page in Journal 2 flashes, even to the point that the lines of the character seem indented into the screen and fade from the outside in after the screen goes black.
- There are some changes between the animatic and the official theme song:
- In the animatic version, Mabel and Dipper arrive on a "Fast Dog" bus. It is changed to "Speedy Beaver" in the final version.
- One of the photos appears to be a robot, but was replaced with the Summerween Trickster.
- The photo of the gnome has a bite out of it on the right side.
- There is a picture of three spaceships and a monster, but they were replaced with the picture of the pterodactyl and a clawed hand. (The picture of three spaceships is flashed on Bill Cipher's body in 'Dreamscaperers'.)
- The totem pole is on the left hand side of the Mystery Shack in the animatic version, while it is on the right hand side on the final version.
- The matrix in the Opening Ending Image represents a scalar, rotation and translation matrix (also known as a transformation matrix), used to perform linear transformations.
- A clip towards the end of the Gravity Falls theme song shows gravity rising and falling (hence Gravity Falls) with Mabel lying on the ground and Dipper reading the journal. This is an allusion to episode 11 of Season 2 "Not What He Seems," and it even references the theme song directly with a rising black 8-ball in both clips, although the Twins are sleeping in the actual episode.
- Beginning with "A Tale of Two Stans," the full title sequence has the picture of a pterodactyl replaced with a picture of Ford Pines holding Journal #1.
- Much of the animation was done by James Baxter, best known for animating Ariel, Belle, Rafiki, and Quasimodo among other characters.
- The title card flickers from "GRAVITY FALLS" to "JUDYLWB IDOOV," which, using the show's Caesar cipher, translates to "GRAVITY FALLS." The water tower's inscription also changes to "JUDYLWB IDOOV."
- Instead of Bigfoot appearing for a frame, there is a walking pine tree. This may be due to the fact that the Pines are the ones hiding now, instead of the paranormal phenomena. It may also be just a switch of the places of Bigfoot and the pine trees in the normal version.
- Where it would normally say "Created by Alex Hirsch," in the apocalypse version it says "Created by Bill Cipher."
- When the first apocalyptic version is played backwards, Bill can be heard saying the words "I'M WATCHING YOU NERDS." The second one has him saying only "I'M WATCHING YOU!" sounding much angrier. The final one says "Good bye Gravity Falls," since it's also the final episode of the series.
- The man at the stamp at the end is replaced with his skeleton.
- The pictures are all replaced to have Bill on every one. He also does the same poses as the pictures. (Not counting one of them)
- The sign with a ? mark and four letters saying "what" is replaced with a picture of Bill's body and four letters now spelling his name. He can also be heard laughing in the background.
- 8 Ball, Teeth, Keyhole and Hectorgon all replace Dipper (Although his skeleton can be seen), Mabel and Stan, in the intro. Keyhole running with a box full of keys and the keys falling out is similar to how Stan runs with the cash register and dollar bills fall out. Hectorgon tipping his hat over also replaces Stan moving his eye patch to his left eye.
- The monster in the campfire scene is replaced with Bill. The people now camping in the same scene are now Grenda Grendinator, Sheriff Blubs, Manly Dan, and Tyler.
- The page which formerly held Bill inside is now ripped with the rip in the shape of Bill's body.
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