- Main article: Arachnimorphs
Arachnimorphs, also known as Spider People, are seen in "Roadside Attraction" as attractions for tourists. They can disguise as humans and lure their victims with their charisma.
- Main article: Bigfoot
Bigfoot, also known as the Sasquatch, is a beast shown for one frame in Gravity Falls' opening credits in the woods, looking at the camera. It is an allusion to the famous film that allegedly contains footage of Bigfoot. Grunkle Stan has made a "Sascrotch," a parody of the Sasquatch that wears underwear.
- Main article: Cooler monster
The Cooler monster is a brain-like creature that Dipper finds in the ice cooler at the Dusk 2 Dawn, in the episode "The Inconveniencing" It is unknown whether this is an independent creature or simply a creation of Ma and Pa Duskerton's. The latter is more likely, as the cooler monster is gone when Dipper checks the ice cooler again. It is probably the ghosts attempting to scare away the teenagers.
- Main article: Dipper clones
In "Double Dipper," Dipper and Mabel use Stan's old photocopy machine and then discover that it is able to clone life-forms, which disintegrate if they come in contact with liquid. All the band members of Sev'ral Timez are clones as well.
Cursed Egyptian super termites
- Main article: Cursed Egyptian super termites
Cursed Egyptian Super Termites are a species of insect that behave similarly to regular termites, though they are much more destructive. They are most likely featured in 2. Gideon Gleeful tried to use them to claim the Mystery Shack in "Dreamscaperers."
Cursed wax figures
- Main article: Wax figures
Stan Pines reveals a bunch of wax figures he had in the Mystery Shack, not knowing that they are cursed to come to life. He is not the original owner, as he stole them from a garage sale.
- Main article: Bill Cipher
Demons are featured in Journal 2 and 3. Bill Cipher is a dream demon that can be released into a person's mind. Demon caterpillars were mentioned by Gideon in "Little Dipper." During a flashback in "The Last Mabelcorn," Bill tells Ford that he can't stop his demons cohorts from coming into Gravity Falls' dimensions.
- Main article: Dinosaurs
- Main article: Pterodactyl
The pterodactyl is an ancient beast that resides in a land trapped in time. In "Land Before Swine," it takes the roof of a cop car and kidnaps Waddles. Later, the pterodactyl's baby hatches and, to the horror of Mabel, Dipper, and Soos, swallows Old Man McGucket whole.
- Main article: Eye-Bats
- Main article: Fairies
A fairy is briefly seen in "Land Before Swine" before Soos kills it with a flyswatter. While looking for ideas to defeat Gideon in Journal 3, Dipper mentions a page describing a "barf fairy." A fairy is seen again in "Dungeons, Dungeons, and More Dungeons," but Stan swats it when it landed on his back.
- Main article: Floating Eyeballs
As the name implies, Floating Eyeballs are eyeballs with no retinal cords that float in the air. They have not been shown in the show, but the intro depicts eyeballs in a jar looking at the camera. They have only been mentioned in a page in Journal 3.
- Main article: Flying skulls
Flying skulls are a type of creature within Gravity Falls, Oregon that resemble one-eyed skulls with bat wings. Although they have not yet appeared in any episodes, they serve as enemies in the games "Fright Night" and "Rumble's Revenge."
- Main article: Ghosts
Ghosts are incorporeal beings of people or spirits that have not passed on after death. According to 3, ghosts always have a reason for staying in the mortal world. So far, only two have been seen. In the episode "The Inconveniencing," they are known as "Ma and Pa." Dipper was "basically a ghost" when Bill took over his body, though it is unknown whether he was truly a ghost or Bill Cipher was simply comparing him to one.
- Main article: .GIFfany
.GIFfany is a digital girl haunting the video game Romance Academy 7. In "Soos and the Real Girl" she said that programmers tried to delete her so instead, she deleted them. Despite seeming sweet and loving towards her owner, if the owner gets on her bad side, she can be a nightmare.
- Main article: Gnomes
Gnomes are small men who live in the forest of Gravity Falls. They seem to have an extreme level of coordination with each other, and are able to form one enormous gnome monster simply by latching onto each other and moving according to a leader's direction. According to Journal 3, gnomes have no known weakness (until Gideon Rises when it's revealed that Dipper put "Leaf Blowers" in the space). There is also no known danger or threat from the gnomes. They seem to be somewhat dysfunctional without a head gnome directing or commanding them.
- Main article: Gobblewonker
The Gobblewonker is a Loch Ness-like monster living in Lake Gravity Falls. Though the Gobblewonker that Dipper and Mabel discover in "The Legend of the Gobblewonker" is only a machine made by Old Man McGucket, it is shown that there is a real Gobblewonker living in the lake.
- Main article: Gremloblin
The Gremloblin is a monster that appears in "Boss Mabel," in Dipper's attempt to create an exhibit for the Mystery Shack that was not a hoax. It is a hybrid of a Gremlin and a Goblin. It was put in a cage as a new attraction, but caused a couple to visualize their worst nightmare, and they were sent to the hospital. If it is exposed to water it becomes angrier and scarier.
- Main article: Hide Behind
The Hide Behind is a creature based on real folklore briefly seen in the "The Hide-Behind." The Hide Behind is a tall and lanky creature that emits a rattling sound who typically follows lumberjacks in the woods behind them, but is never seen as it quickly hides before anyone can look at it. Dipper attempts to catch a glimpse of the beast, but never manages to do so, and reluctantly accepts the monster as just a legend. The teaser poster for Season 2 shows that the Hide Behind will be returning in some form.
Island Head Beast
- Main article: Island Head Beast
The Island Head Beast is a massive creature living in Lake Gravity Falls. It dwells just beneath the surface, with only its top showing. When its like his, it resembles an island, but can fly above the water, revealing its hideous human face.
- Main article: Lilliputtians
The Lilliputtians are tiny, golf ball like creatures living in Ye Royal Discount Putt Hutt. They play a key part in how the golf balls the user strikes outcome is. They seem harmless but they've shown to be dangerous little things in "The Golf War".
- Main article: Mailbox
The Mailbox is an omniscient, omnipotent and omnipresent. Found in the woods in "Mailbox," without an address or name, whenever a letter is inserted, a reply will instantly appear inside. When Mabel inserted a video of herself putting 100 gummy worms in her nose, the Mailbox thought it was disturbing, and self destructed.
- Main article: Manotaurs
Manotaurs, similar to mythological Minotaurs, are half man and half bull.Seen in "Dipper vs. Manliness, they are extremely manly, going to great lengths to be physically fit, and often getting in fights with each other at random.
- Main article: Merpeople
Merpeople were briefly mentioned in "Dipper vs. Manliness" by the Manotaurs. They are stated to live in the water. It can be inferred that they are largely the same as mythological merpeople and are some combination of half-man, half-fish. The episode "The Deep End" features Mermando, a merman stuck in the public pool.
- Main article: Multi-Bear
The Multi-Bear is a magical creature seen in "Dipper vs. Manliness" that lives in the mountains of Gravity Falls. It is a bear with eight limbs and eight heads, one of which is extremely intelligent, capable of human speech, and seems to have control over the other heads.
- Main article: Rumble McSkirmish
Rumble McSkirmish is a video game character that appears in the episode "Fight Fighters." He protects Dipper from Robbie under the belief Robbie had killed Dipper's father until Dipper confesses that he lied to Rumble. Rumble McSkirmish is a playable fighter in Fight Fighters, an arcade game that Dipper and Wendy like to play. Once, Dipper brought him into the real world by using the ultimate power code that he found on the lower left side of the arcade game.
- Main article: Shape Shifter
The Shape Shifter is a creature that appears in the episode "Into the Bunker" which has the ability to shape-shift into anyone or anything it sees. It is the result of an experiment most likely performed by the author of the three journals. The Shape Shifter is quite intelligent and has the ability to talk and trick humans easily. The Shape Shifter is currently frozen in the Author's fallout shelter.
- Main article: Summerween Trickster
The Summerween Trickster was a monster shown in the episode "Summerween." It consists of thrown away candy and likes to punish people who don't appreciate all types of candy.
- Main article: Time BabyThe Time Baby is a giant, time-manipulating baby, as well as the tyrannical supreme ruler of the future.
- Main article: The Undead
The Undead are one of the many creatures of Gravity Falls, Oregon to be documented in Journal 3. According to the number six next to its name, it can be deduced that it is the sixth creature to be written about in the book. Zombies have made their first and only appearance in the episode "Scary-oke". Journal 3 writes extensively on them. They are bodies reanimated from the dead, known for their pale skin and bad attitudes. According to the book, they are often mistaken for teenagers because of these traits.
- Main article: Unicorns
Unicorns reside in the Enchanted Forest within Gravity Falls. They are reclusive creatures, lying that their valuable hair can only be claimed by those of pure heart in order to keep humans away.