Twins Dipper and Mabel Pines visit their eccentric great-uncle for a summer in Gravity Falls, Oregon, where he operates the world's most bizarre museum. As soon as the twins arrive in Gravity Falls, they discover something amiss in the remote town.
When Dipper and Mabel hear rumors of a sea monster that lives at the bottom of the local lake, they enlist Soos to take them on a boating expedition to prove it really does exist.
When someone tampers with Mabel's life-size wax statue of Grunkle Stan, she and Dipper set out to find the culprit. Meanwhile, Grunkle Stan mourns over the loss of his wax doppelganger.
Dipper and Mabel discover that their seemingly cherubic new neighbor, Lil' Gideon, happens to be the town's adored psychic. But when Lil' Gideon guilts her into dating him, she and Dipper soon learn that his cuteness can fade all too quickly.
Dipper is invited by Wendy and her teen friends on a trek that leads to an abandoned convenience store that may be haunted.
In a quest to attain manliness, Dipper ventures into the forest to battle the notorious Multi-Bear. Meanwhile, Mabel tries to teach Grunkle Stan how to be attractive to women, particularly the waitress in the local diner, Lazy Susan.
Stan throws a big weekend party to promote the Mystery Shack. Dipper makes clones of himself to impress Wendy. Mabel fights for the Party Queen title in honor of her two friends.
When Dipper and Mabel discover evidence that the reported town founder is a hoax, they set out to expose the historical cover-up and prove that Mabel's silliness is not a bad thing.
Dipper wants to correct a mistake he made in the past with assistance from a time machine. Mabel is overjoyed when she wins a pet pig at a fair.
After being challenged to a video game battle by Robbie, Dipper is shocked when his favorite playable fighter, Rumble McSkirmish, comes to life to defend him. But Dipper soon loses control over Rumble McSkirmish and has to find a way to stop him.
Dipper is self-conscious that Mabel is taller than him and seeks a magic solution. Meanwhile Lil' Gideon takes advantage of Dipper's and Mabel's height discrepancy.
Dipper and Mabel go trick-or-treating in the summer and encounter a candy-loving monster who threatens to devour them if they don't bring him sweet things to eat.
Stan leaves Mabel in charge of the Mystery Shack while he is gone and the power goes to her head.
While Stan, Dipper, Mabel and Soos are falling in a bottomless pit, they tell stories to pass the time.
When Mabel befriends a cute merman trapped in the public pool, she's determined to help him out. Meanwhile, Dipper decides to volunteer as a lifeguard to see Wendy.
The twins discover a hidden room inside the Mystery Shack and compete over who should have it.
When Mabel discovers that her favorite boy band is actually a bunch of imprisoned clones, she sets them free, only to decide on keeping them for herself. Meanwhile, Dipper is convinced that Robbie plans to brainwash Wendy with a secret message hidden inside one of his songs.
When Waddles is snatched by a prehistoric beast, Dipper, Mabel, Stan, Soos, and Old Man McGucket must journey to a mysterious land trapped in time to rescue him.
Dipper, Mabel, and Soos must travel through Grunkle Stan's mind to defeat a tricky dream demon summoned by Lil Gideon.
Li'l Gideon swindles the Mystery Shack away, forcing Grunkle Stan and the kids to move in with Soos. While Stan weighs how he can still care for his grandniece and nephew, they decide to take on Gideon.
