Height-altering crystals can be found deep within the Gravity Falls Forest and, as their name implies, they can change an object's or living being's (animals and humans) size when light shines through them.
At some point before the events of the series, Ford Pines heard legends of miniature buffalo and giant squirrels from the locals, and he soon believed that there were height-altering properties in the forest. He soon came across the crystals and studied the crystals, recording their powers, appearance, and location in Journal 3.
In "Little Dipper," after Mabel teases Dipper for being a millimeter shorter than her, Dipper looks for a way to increase his height. Upon reading about them in Journal 3, he searches for them in the forest, and after tumbling down a hill, he finds them. He removes a crystal and takes it home, where he assembles his crystal flashlight and uses it to change the size of a chess pawn and later himself. When Mabel discovers what her brother is doing, she tries to steal it from him and they fight over the flashlight. When Mabel accidentally reveals its function to Gideon Gleeful, he uses it to shrink the twins and accidentally Soos. Later, he attempts to shrink Grunkle Stan, but to no avail. Dipper and Mabel grow themselves back to their full heights and smash the crystal, but after realizing they forgot to regrow Soos, they glue it back together.
In "Gideon Rises," the height-altering crystals page from Journal 3 makes an appearance while Dipper and Mabel are thinking of a way to defeat Gideon; it is later seen again in the end credits.
In "Weirdmageddon 3: Take Back The Falls," Dipper recreates the crystal flashlight to use as a weapon in the final fight against Bill Cipher. He later uses it to increase the size of the cage Bill puts him and Mabel in, making it large enough for them to slip through the bars. Moments later, Mabel uses it to enlarge her hand, allowing her to punch a hole in the Fearamid.
To make for a more efficient use, Dipper attached a crystal to the lens of a flashlight. By flipping the crystal to a specific side and turning the flashlight on, a beam of light will fire blue light for a size increase and pink for a size reduction and will cause the subject to grow or shrink, with a more drastic change occurring the longer the flashlight is on. When the desired size is reached, the user should turn off the flashlight.
- The Twin Mystery Vortex of Doom (pictured)
- Attic Stuff Golf
- Rumble's Revenge
- Li'l Gideon Shrinks Back
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