Fuse was amazed that, like Nowhere, Gravity Falls was inhabited by monsters. At the time of the Fusion Invasion Mabel was launched by an otherwise harmless beam of light all the way to Murky Woods; it is unclear who was behind this. Though Dipper has sworn revenge against Planet Fusion, his attempts to hinder the infection of the area by Fusion Matter have so far proven ineffective.
Later on, it is revealed that Mabel was exiled to Murky Woods by none other than Li'l Gideon, Mabel and Dipper's sworn enemy, who had escaped from prison, stolen Dipper's journal, and gone to Volcano Mountain to conduct its unholy rituals.
Following the devastation of the surrounding kingdoms, Princess Anna and Queen Elsa of Arendelle were sent here to hide from Fuse. Though Anna longs to leave the town and explore her new world, Elsa seems resigned to staying in Gravity Falls, if only to keep Anna and herself safe.