The Gravity Falls Forest is a large area surrounding most of Gravity Falls, Oregon. The forest is teeming with mystical entities, including a variety of supernatural and paranormal creatures, objects, etc.
In "Tourist Trapped," Stan Pines tells the employees of the Mystery Shack to go and put up signs in the forest to advertise the Shack. After a brief discussion, Dipper is elected as the one to put them up, and begrudgingly ventures into the forest to do so. In the forest, while Dipper is nailing up the signs, he discovers that one of the trees makes a metallic ringing sound as the nail is hammered in. He then discovers a secret panel in the fake tree, which conceals a strange box with two switches on it, one of which reveals the hiding place of Journal 3.
Later on, the gnomes, who are disguising themselves as a teenage boy named Norman, bring Mabel there to attempt to force her to marry them and become their gnome queen. Dipper rescues Mabel in the Mystery Cart and they flee the forest to fight the gnomes at the Mystery Shack.
Part of the forest contains height-altering crystals, as shown in "Little Dipper." These crystals have caused legends of tiny buffalo and giant squirrels and has created miniature deer, gigantic butterflies, a small puma, and giant caterpillars. Dipper takes one of the crystals and attaches it to a flashlight to take advantage of its powers (which by flipping the crystal to a specific side, switch on the button and point it at the target, the ray will increase or decrease the target).
In "Boss Mabel," Dipper captures a Gremloblin in an unknown area of the forest to bring into the exhibit of the Mystery Shack, to show something that wasn't one of Stan's hoaxes. Ironically, everybody else thought it wasn't real.
In "Gideon Rises," Dipper and Mabel go into the forest to recruit the gnomes.
In "Into the Bunker," Wendy finds a branch lever on a metal tree which leads to the bunker, and at the end of the episode, Dipper admits his feelings to a Shape Shifter who pretended to be a drowned Wendy. The actual Wendy overhears, and they later talk things over on a log outside the bunker.
In "Little Gift Shop of Horrors," it is revealed that somewhere deep within the forest are mushrooms called percepshrooms, which improve the user's brain power when mashed up and applied to the forehead overnight.
In "Dipper and Mabel vs. the Future," Mabel runs off into the forest as a result of overhearing Dipper's plans to stay in Gravity Falls with Ford.
In "Weirdmageddon Part 1," the Forest's denizens are shown fleeing from Bill Cipher's emergence, stampeding past Dipper and Ford, who had come out to look for Mabel.
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